Pharmaceutical and Clinical Calculations PDF

PHARMACEUTICAL AND CLINICAL CALCULATIONS PHARMACEUTICAL AND CLINICAL CALCULATIONS 2nd EDITION Mansoor A. Khan, Ph.D. Indra K. Reddy, Ph.D. C RC P R E S S Boca Raton London New York Washington, D.C.  Library of Congress Cataloging-in-Publication Data M...

PHARMACEUTICAL AND CLINICAL CALCULATIONS PHARMACEUTICAL AND CLINICAL CALCULATIONS 2nd EDITION Mansoor A. Khan, Ph.D. Indra K. Reddy, Ph.D. C RC P R E S S Boca Raton London New York Washington, D.C.  Library of Congress Cataloging-in-Publication Data Main entry under title: Pharmaceutical and Clinical Calculations, Second Edition Full Catalog record is available from the Library of Congress This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and infor- mation, but the authors and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Visit the CRC Press Web site at www.crcpress.com © 2000 by CRC Press LLC Originally Published by Technomic Publishing No claim to original U.S. Government works International Standard Book Number 1-56676-812-8 Library of Congress Card Number 99-69344 Printed in the United States of America 2 3 4 5 6 7 8 9 0 Printed on acid-free paper  TABLE OF CONTENTS Foreword Preface Chapter 1. Prerequisite Mathematics Review Numbers and Numerals Arabic and Roman Numerals Fractions Decimals Ratio and Proportion Percentage Percent Concentration Expressions Dilution and Concentration Density and Specific Gravity Chapter 2. Systems of Measurement The Metric System Apothecaries’ System The Avoirdupois System The Household System Interconversions Chapter 3. Prescription and Medication Orders Types of Prescriptions Components of Prescriptions Label on the Container Medication Order  Common Latin Terms and Abbreviations Medications and Their Directions for Use Prescription Problems Errors and Omissions Chapter 4. Principles of Weighing and Measuring Prescription Balance and Sensitivity Requirement Aliquot Method for Solids Liquid Measurements Aliquot Method for Liquids Chapter 5. Calculations Involving Oral Liquids Calculations Associated with Bulk Preparations Calculation of Doses Percentage Strength Calculations of Oral Liquids Dilution and Concentration Milliequivalent Calculations of Oral Electrolyte Solutions Dosage Calculations Involving Milliequivalents Chapter 6. Calculations Involving Capsules, Tablets, and Powder Dosage Forms Strength of Dosages Extemporaneous Filling of Capsules Compounding Tips and Calculations for Filling Powder Prescriptions Chapter 7. Calculations Involving Ointments, Creams, and Other Semisolids Compounding Tips Calculations Associated with Bulk Preparations Percentage Strength Calculations of Semisolid Preparations Dilution and Concentration Chapter 8. Calculations Involving Topical Ophthalmic, Nasal, and Otic Preparations Isotonicity Calculation of Dissociation (I) Factor Sodium Chloride Equivalents of Drug Substances Isotonicity Adjustments by Sodium Chloride Equivalent Methods Tonicity Agents Other than Sodium Chloride Isotonicity Adjustments by Cryoscopic Method Volumes of Iso-Osmotic Solutions pH Adjustment  Conversion of Hydrogen Ion Concentration to pH Conversion of pH to Hydrogen Ion Concentration Buffers Calculations Involving pH Value of a Buffer Molar Ratio of Buffer Components in a Buffer Chapter 9. Calculations Involving Suppositories Displacement Value Preparation of Suppositories with Cocoa Butter Chapter 10. Calculations Invovling Injectable Medications Rate of Flow of Intravenous Fluids Insulin Dosage Heparin Dosage Calculations Involving Reconstitution of Dry Powders Milliequivalents and Milliosmoles Chapter 11. Calculations Involving Nutrition Calculations of Calories Parenteral Hyperalimentation Resting Energy Expenditure (REE) Calculations Geriatric Nutrition Pediatric Nutrition Chapter 12. Calculation of Doses and Dose Adjustments Plasma Concentration Versus Time Profile Some Pharmacokinetic Parameters Fraction of Drug Absorbed and the Dosing Interval Clearance Loading and Maintenance Doses Dose Adjustments in Renal Failure Dose Adjustments in Hepatic Failure Chapter 13. Pediatric and Geriatric Dosing Dosage Calculations Based on Age Dosage Calculations Based on Body Weight Dosage Calculation Based on Body Surface Area Dosage Regimen in Patients Using Aminoglycosides Critical Care Pediatric Critical Care Chapter 14. Calculations Involving Immunizing Agents and Vaccines Bacterial Vaccines  Viral Vaccines Toxoids Chapter 15. Calculations Involving Radiopharmaceuticals Units of Radioactivity Half-Life of Radiopharmaceuticals Mean Life Radioactive Decay of Radioisotopes Percentage Activity Dispensing of Radiopharmaceuticals Review Problems Answers to Practice Problems Answers to Review Problems Appendix A Appendix B Appendix C Appendix D Appendix E Suggested Readings  FOREWORD Pharmacists for the 21st Century must be patient-focused clinical prac- titioners. While the pharmacist’s primary duty has always been to ensure that his/her patients receive accurately prepared, highest quality therapeutic agents, today’s pharmacist must also be knowledgeable and skilled at calculating individualized doses of the various medications by considering the unique clinical characteristics of his/her patients. The goal is to ensure that all patients receive the highest quality pharmaceutical care possible by minimizing poten- tial medication related problems. When all the elements of patient care are considered, our patients will receive optimal outcomes from their drug therapy. This is the critical duty of today’s pharmacist. A basic premise of delivering quality pharmaceutical care is ensuring that the pharmaceutical products that the pharmacist prepares and dispenses to his/ her patients contain the correct dose of the medication. Thus, the first steps toward patient-centered pharmaceutical care are learning how to accurately interpret a prescription or medication order, calculate the appropriate amounts of ingredients and precisely weigh and measure ingredients. Following closely is learning how to accurately calculate and measure the appropriate dose of medication that meets the patient’s unique clinical needs. In Pharmaceutical and Clinical Calculations, second edition, Drs. Mansoor Khan and Indra Reddy have provided a contemporary resource that can help pharmacy students learn the basic principles of how to accurately interpret prescriptions and medication orders, measure, calculate and compound quality dosage forms. In the latter chapters, the student can learn multiple methods to accurately and safely dose patients. The computational methods to accom- plish these ends are clearly presented, and the examples used to demonstrate the concepts are relevant to contemporary practice. Pharmacy students will be presented with these very same problems in live patients during clinical rotations. This book can also be a reference source for practitioners who need to ‘‘refresh’’ basic concepts in measurements and calculations to ensure safe and effective drug therapy for their patients. The concepts and methods pre- sented serve as foundational knowledge and skills for all patient-centered pharmacists as they seek to serve their patients with the highest level of care. ARTHUR A. NELSON, JR., R.PH., PH.D. Dean and Professor School of Pharmacy Texas Tech University Health Sciences Center Amarillo, Texas  PREFACE Pharmaceutical and clinical calculations are critical to the delivery of safe, effective, and competent patient care and professional practice. The current shift in pharmacy education from product-oriented practices to patient-oriented practices makes the calculations even more challenging. Many students in pharmacy and health science programs and beginning practitioners in the related areas struggle to master these essential skills. Although many books are available on theoretical and applied concepts of calculations involving medication dosages, only a few reflect the emphasis on pharmaceutical care and the contemporary pharmacy practice. The present text is designed for Pharm. D. or undergraduate students in baccalaureate curriculum in pharmacy, contemporary pharmacy practice pro- fessionals, and other health care professionals. It provides calculations involv- ing various dosage forms in a well-organized and easy to comprehend manner. The book contains fifteen chapters. Chapter 1 presents a review of prerequisite mathematics, which includes Roman numerals, fractions and decimals, ratios and proportions, dilution and concentration expressions, and density and specific gravity. Chapter 2 deals with systems of measurement. The metric system is emphasized since it is federally mandated. Though the apothecary system of measurement is fast declining, a few prescriptions still appear with these units in professional practice. An explanation of various systems of measurement and the interconversions are provided in this chapter. Chapter 3, ‘‘Prescription and Medication Orders,’’ not only provides a thorough explanation of types and components of prescriptions, but also lists abbreviations, most commonly pre- scribed drugs with their brand and generic names, directions for use, and errors and omissions in prescriptions. In Chapter 4, principles of weighing and measur- ing including the aliquot method for solids, as well as liquids, are discussed.  Chapters 5 through 7 deal with essential calculations involving different dosage forms including oral liquid, solid, and semisolid dosage forms. Chapter 5 embodies calculations pertaining to syrups, elixirs, and suspensions. The calculations involving percentage strength, dilution and concentration, and milliequivalents and milliosmoles are included in this chapter. Extemporane- ous filling of powders in capsules and calculations involving trituration, leviga- tion, and geometric mixing are provided in Chapter 6. Calculations involving semisolid dosage forms including alligation alternate and alligation medial are presented in Chapter 7. A variety of dosage forms are applied topically to the eye, nose, and ear. Chapter 8 provides calculations involving isotonicity, pH, and buffering of topical dosage forms. Chapter 9 deals with calculations involving supposito- ries. Chapter 10 features calculations associated with parenteral medications, which include rate of flow of intravenous fluids, insulin and heparin administra- tion, and reconstitution of powdered medications. Calculations involving calo- ries, nitrogen, protein-calorie percentage, parenteral hyperalimentation, and resting energy expenditure assessments are presented in Chapter 11. The clinical calculations are included in the book to provide necessary background for the clinical pharmacy practice. Knowledge of clinical pharma- cokinetics is essential in providing an optimum drug concentration at the receptor site to obtain the desired therapeutic response and to minimize the drug’s adverse or toxic effects. For an optimal therapeutic response, the clinical pharmacist must select a suitable drug and determine an appropriate dose with the available strengths and a convenient dosing interval. To perform this task, serum or plasma drug concentrations have to be analyzed, the pharmacokinetic parameters have to be evaluated, the drug dose has to be adjusted, and the dosing interval needs to be determined. Chapter 12 deals with the determination of pharmacokinetic parameters, loading and maintenance doses, and tailoring of doses for patients with renal damage. Chapter 13 presents calculations involving doses and dose adjustments that are required in pediatric and geriatric patients. Emphasis is placed on the calculations involving the use of aminogly- cosides and critical care. Calculations involving strengths of vaccines and toxoids are presented in Chapter 14. Chapter 15 deals with calculations involv- ing radiopharmaceuticals including mean life, half-life, radioactive decay, and percentage activity. Key concepts are highlighted throughout the text for emphasis and easy retrieval. The examples presented throughout the text reflect the practice environment in community, hospital, and nuclear pharmacy settings. Answers to all the practice and review problems are provided at the end of the book. Although every effort was made to maintain the accuracy of doses and other product related information, the readers should not use this book as the only source of information for professional practice. The authors would like to acknowledge Drs. Michael DeGennaro, Amir Shojaei, and Abdel-Azim Zaghloul for their helpful comments and suggestions on various chapters of the book, Dr. Steven Strauss and Ms. Susan Farmer of Technomic Publishing Company, Inc. for their excellent cooperation and coordination, and Mr. Fred Mills, R.Ph., for providing specific case studies and information on errors and omissions. The authors would like to acknowl- edge with thanks the faculty at several pharmacy schools for their active participation in the survey prior to undertaking the task of writing this book. The participation and input by these faculty not only made us realize the immediate need for this book, but also helped us organize it. Finally, the authors would like to thank their wives, Ms. Rehana Khan and Ms. Neelima Reddy for their inspiration, encouragement, and forbearance throughout this endeavor, which made work a pleasure. MANSOOR A. KHAN INDRA K. REDDY  CHAPTER 1 Prerequisite Mathematics Review NUMBERS AND NUMERALS A number is a total quantity or amount, whereas a numeral is a word, sign, or group of words and signs representing a number. ARABIC AND ROMAN NUMERALS Arabic Numerals Arabic numerals, such a 1, 2, 3, etc., are used universally to indicate quantities. These numerals, which are represented by a zero and nine digits, are easy to read and less likely to be confused. Roman Numerals Roman numerals are used with the apothecary’s system of measurement to designate quantities on prescription. In the Roman system of counting, letters of the alphabet (both uppercase and lowercase) such as I or i, V or v, and X or x are used to designate numbers. A few commonly used Roman numerals and their Arabic equivalents are given in Table 1.1. In the usage of Roman numerals, the following set of rules apply: (1) When a Roman numeral is repeated, it doubles its value; when a Roman numeral is repeated three times, it triples its value. 1  TABLE 1.1. Roman Numerals and Their Arabic Equivalents. Roman Arabic Num eral Num eral I (or i) 1 II (or ii) 2 III or (iii) 3 IV (or iv) 4 V (or v) 5 VI (or vi) 6 VII (or vii) 7 VIII (or viii) 8 IX (or ix) 9 X (or x) 10 XX (or xx) 20 XXX (or xxx) 30 L (or l) 50 C (or c) 100 D (or d) 500 M (or m) 1000 Examples: I = 1, II = 2, III = 3 X = 10, XX = 20, XXX = 30 (2) When Roman numeral(s) of lesser value follows one of a greater value, they are added. Examples: VII = 5 + 1 + 1 = 7 XVI = 10 + 5 + 1 = 16 (3) When Roman numeral(s) of lesser value precedes one of a greater value, they are subtracted from the greater value numeral. Examples: IV = 5 − 1 = 4 IX = 10 − 1 = 9 2 (4) When Roman numeral of a lesser value is placed between two greater values, it is first subtracted from the greater numeral placed after it, and then that value is added to the other numeral(s) (i.e., subtraction rule applies first, then the addition rule). Examples: XXIX = 10 + 10 + (10 − 1) = 29 XIV = 10 + (5 − 1) = 14 (5) Roman numerals may not be repeated more than three times in succession. Example: 4 is written as IV but not as IIII (6) When possible, largest value numerals should be used. Example: 15 is written as XV but not as VVV Roman numerals are sometimes combined with the abbreviation for one half, ss. The abbreviation should always be at the end of a Roman numeral. Generally, Roman numerals are written in lowercase when used with ss, such as iss to indicate 11⁄2. FRACTIONS A fraction is a portion of a whole number. Fractions contain two numbers: the bottom number (referred to as denominator) and the top number (referred to as numerator). The denominator in the fraction is the total number of parts into which the whole number is divided. The numerator in the fraction is the number of parts we have. A proper fraction should always be less than 1, i.e., the numerator is smaller than the denominator. Examples: 5/8, 7/8, 3/8 A proper fraction such as 3/8 may be read as ‘‘3 of 8 parts’’ or as ‘‘3 divided by 8.’’ An improper fraction has a numerator that is equal to or greater than the denominator. It is therefore equal to or greater than one. 3 Examples: 2/2 = 1, 5/4, 6/5 To reduce the improper fraction, divide the numerator by the denominator. Examples: 8/8 = 8 8=1 6/4 = 6 4 = 12⁄4 9/4 = 9 4 = 21⁄4 To reduce the fraction to its lowest terms (which may be referred to as ‘‘simplifying the fraction’’), find the largest number (referred to as greatest common divisor) that will divide evenly into each term. Examples: 15/20 = 15 5/20 5 = 3/4 12/18 = 12 6/18 6 = 2/3 7/21 = 7 7/21 7 = 1/3 Addition of Fractions To add fractions, the following steps may be used: (1) Find a least common denominator or the smallest number that divides all the denominators evenly. (2) Change each fraction so that it has that denominator but retains its original value. (3) Add the numerators. (4) Reduce the resulting fraction to its lowest terms. Example: 4/6 + 2.4/4 + 2/5 4  By changing each fraction such that it has the same denominator without changing the value of the fraction, we get: 40/60 + 36/60 + 24/60 = 100/60 = 140⁄60 or 12⁄3 Some numbers are expressed as mixed numbers (a whole number and a fraction). To change mixed numbers to improper fractions, multiply the whole number by the denominator of the fraction and then add the numerator. Examples: 105⁄8 = 85/8 35⁄6 = 23/6 Subtraction of Fractions To subtract fractions, the following steps may be used: (1) Find a least common denominator or the smallest number that is divided by all the denominators evenly. (2) Change each fraction so that it has that denominator but retains its original value. (3) Subtract the numerators. (4) Reduce the resulting fraction to its lowest terms. Example: 5/6 − 4/5 = 25/30 − 24/30 = 1/30 If one of the numbers is a mixed number, change it to an improper fraction and then subtract. 5 Example: 41⁄4 − 4/5 = 17/4 − 4/5 = 85/20 − 16/20 = 69/20 or 39⁄20 Multiplication of Fractions To multiply fractions, following steps may be used: (1) Fractions are multiplied by multiplying the two numerators to obtain the numerator of the answer and then multiplying the two denominators to obtain the denominator of the answer. Example: 3/5 × 1/2 = 3/10 (2) Reduce your answer to lowest terms, when possible. (3) When possible, divide the numerator of any of the fractions and the denominator of any of the fractions by the same number. Then multiply the denominators and reduce the fraction to its lowest terms. Example: 2/3 × 7/8 = 1/3 × 7/4 = 7/12 (4) To multiply a fraction with a whole number, assume the denominator of the whole number to be 1. Then multiply the numerator and denominator in the same way as explained above in step 1. Example: 4 × 5/6 = 20/6 = 10/3 or 31⁄3 6 (5) When there are mixed numbers in the problem, change them to improper fractions and then multiply. Example: 21⁄3 × 31⁄4 = 7/3 × 13/4 = 91/12 = 77⁄12 In the division of fractions, the following terms are used: Dividend = The number to be divided Divisor = The number by which the dividend is divided Quotient = The number obtained by dividing the dividend with the divisor, i.e., dividend divisor = quotient; this expression may be read as ‘‘divi- dend is divided by divisor to obtain the quotient’’ Division of Fractions To divide a whole number or a fraction by a proper or improper fraction, invert the divisor and multiply. Example: 4/5 2/3 = 4/5 × 3/2 = 6/5 or 11⁄5 Note: Whole numbers are assumed to have a denominator of 1. When there is a mixed number in the problem, first change it to an improper function, then invert the divisor, and multiply. Example: 46⁄9 6/8 = 42/9 6/8 7 9  = 42/9 × 8/6 = 7/9 × 8/1 = 56/9 or 62⁄9 DECIMALS Decimals are another means of expressing a fractional amount. A decimal is a fraction whose denominator is 10 or a multiple of 10. Example: 0.8 = 8/10 0.08 = 8/100 0.008 = 8/1000 A decimal mixed number is a whole number and a decimal fraction. Example: 4.3 = 43⁄10 Each position to the left of the decimal is ten times the previous place and each position to the right is one-tenth the previous place. The position to the left or right of the decimal point is referred to as place value, which determines the size of the denominator. Figure 1.1 indicates the place value of the numerals to the left and right of the decimal point. Adding zeros to a decimal without changing the place value of the numerals does not affect the value of the number. However, adding or subtracting zeros between the decimal point and the numeral does change the value of the number. Example: 0.4, 0.40, or 0.400; all these represent four-tenths But, 0.4 = four-tenths 8  FIGURE 1.1. Place values of numerals. 0.04 = four-hundredths 0.004 = four-thousandths Addition and Subtraction To add or subtract decimals, line up the numbers so that all numbers with the same place value are in the same column, and then add or subtract. Examples: Addition: 16.24 8.12 12.62 36.98 Subtraction: 43.78 − 8.43 35.35 Multiplication To multiply decimals, multiply the numerals as usual and move the decimal point in the answer to the left as many places as there are in the sum of the decimal places in the two numbers being multiplied. 9 9 Example: 8.23 × 6.76 (sum of the decimal places in the two numbers is 4) 823 × 676 = 556348 55.6348 Division To divide decimals, following steps may be used: (1) Change the divisor to a whole number by moving the decimal point to the right. (2) Move the decimal point in the dividend to the right the same number of places. (3) Divide. (4) Place the decimal point in the quotient above the decimal in the dividend. Example: Divide 26 by 2.006 Change the divisor and dividend to whole numbers by moving the decimal point to the right: Dividend = 26000 Divisor = 2006 Divide 12.961 2006. ) 26000.000 2006 5940 4012 1928 0 1805 4 122 60 120 36 2 240 2 006 234 10 Practice Problems (1) Write the following in Roman numerals: a. 28 b. 15 c. 17 d. 23 (2) Convert the following Roman numerals to Arabic numerals: a. xlvi b. lxxiv c. xlvii d. xxxix (3) Perform the following operations and indicate your answer in Arabic numbers: a. XII + VII b. XXVI − XII c. XXIV VI d. XIX × IX (4) Perform the following operations and indicate your answer in Roman numbers: a. 18 + 13 b. 48 6 c. 625 25 d. 17 + 15 + 23 − 6 (5) Interpret the quantity in each of the following: a. Caps. no. lxiv b. Tabs no. xlvii c. Pil. no. xlv d. Caps. no. xvi (6) A bottle of Children’s Tylenol® contains 30 teaspoonfuls of liquid. If each dose is 1⁄2 teaspoonful, how many doses are available in this bottle? (7) A prescription contains 3/5 gr of ingredient A, 2/4 gr of ingredient B, 6/20 gr of ingredient C, and 4/15 gr of ingredient D. Calculate the total weight of the four ingredients in the prescription? 11 9  (8) A patient needs to take 1⁄2 tablet of Medication A and 11⁄2 tablets of Medication B, both three times a day for 7 days. How many tablets does the patient receive over seven days for each of the medication? (9) A pharmacist had 10 g of codeine sulfate. If he used it in preparing 5 capsules each containing 0.025 g, 10 capsules each containing 0.010 g, and 12 capsules each containing 0.015 g, how many g of codeine sulfate were left after he prepared all the capsules? (10) A tablet contains 1/20 gr of ingredient A, 1/4 gr of ingredient B, 1/12 gr of ingredient C, and enough of ingredient D to make a total of 20 gr. How many grains of ingredient D are in the tablet? RATIO AND PROPORTION Ratio A ratio indicates a relation or comparison of two like quantities. It can be expressed as a quotient, a fraction, a percentage, or a decimal. Examples: Quotient 1 2 = 1:2 or 1 is to 2 Fraction 1/4 = 1:4 or 1 is to 4 Percentage 20% or 20:100 or 20 is to 100 Decimal 0.15 = 15/100 = 15:100 or 15 is to 100 If the two terms of a ratio are multiplied or divided by the same number, the value of the ratio will not change. For example, the ratio of 30:6 (or 30/ 6) has a value of 5. If both terms are multiplied by 3, the ratio becomes 90:18 (or 90/18) and still has the same value of 5. Ratios having the same values are equivalent. Cross products of two equiva- lent ratios are equal, i.e., the product of the numerator of one and the denomina- tor of the other always equals the product of the denominator of one and the numerator of the other. Example: 4/5 = 12/15 12 Cross products of the above equivalent ratios are equal, i.e., 4 × 15 = 5 × 12 = 60 Proportion Two equal fractions can be written as a proportion. Thus, a proportion is a statement of equality between two fractions or ratios. The following forms may be used to express the proportions: a:b = c:d a:b::c:d a/b = c/d Examples of equal fractions written as proportions: 12/15 = 4/5 3/6 = 21/42 8/16 = 22/44 A proportion when written as 1/2 = 5/10 can be read as ‘‘one is to two as five is to ten,’’ and 8/16 = 22/44 may be read as ‘‘8 is to 16 as 22 is to 44.’’ When a proportion is written as 1:2 = 5:10, the outside numbers (1 and 10) may be referred to as ‘‘extremes’’ and the inside numbers (2 and 5) as ‘‘means.’’ When two fractions are equal, their cross products are also equal. Stated in another way, the product of the extremes equals the product of the means. Therefore, 1/2 = 5/10 can be written as 1 × 10 = 2 × 5. If one of the terms in a proportion is unknown, it can be designated as X. The value of ‘‘X’’ can be calculated by setting up a proportion and solving for the unknown, X, as follows: (1) Find the product of means and extremes, i.e., cross multiply the terms. (2) Solve for X by dividing each side of the equation by the number that X was multiplied by. Example: 1/2 = X/4; find the value of X 1:2 = X:4; 1 × 4 = 2 × X or 4 = 2X 13 9  4/2 = 2X/2 X=2 Use of proportion is very common in dosage calculations, especially in finding out the drug concentration per teaspoonful or in the preparation of bulk or stock solutions of certain medications. In a given proportion, when any three terms are known, the missing term can be determined. Thus, for example, if a/b = c/d, then: a = bc/d b = ad/c c = ad/b d = bc/a For example, to find out how many milligrams of the drug demerol is present in 5 mL when there are 15 mg of demerol in 1 mL, a proportion can be set as: drug:volume = drug:volume 15 mg:1 mL = X mg:5 mL X = 15 × 5 = 75 mg PERCENTAGE The word percent means hundredths of a whole and is represented by the symbol %. Therefore, 1% is the same as the fraction 1/100 or the decimal fraction 0.01. Examples: 5% = 5/100 or 1/20 To express a percent as a decimal, note that percent means division by 100; with decimals, division by 100 is accomplished by moving the decimal point two places to the left. Examples: 50% = 0.50 5% = 0.05 14  To change a fraction to a percent, first change the fraction to a decimal and then multiply it by 100. If the number is already presented as a decimal, directly multiply by 100. Examples: 1/25 = 0.04 = 4% 1/20 = 0.05 = 5% The word percentage indicates ‘‘rate per hundred’’ and indicates parts per 100 parts. A percentage may also be expressed as a ratio, given as a fraction or decimal fraction. For example, 15% indicates 15 parts of 100 parts and may also be expressed as 15/100 or 0.15. To convert the percentage of a number to equivalent decimal fraction, first drop the percent sign and then divide the numerator by 100. Examples: 15% of 100 is same as 15/100, or 0.15 0.15% = 0.15/100 = 0.0015 PERCENT CONCENTRATION EXPRESSIONS The concentration of a solution may be expressed in terms of the quantity of solute in a definite volume of solution or as the quantity of solute in a definite weight of solution. The quantity (or amount) is an absolute value (e.g., 10 mL, 5 g, 5 mg, etc.), whereas concentration is the quantity of a substance in relation to a definite volume or weight of other substance (e.g., 2 g/5 g, 4 mL/5 mL, 5 mg/l mL, etc.). (1) Percent weight-in-volume, % w/v: number of grams of a constituent (sol- ute) in 100 mL of liquid preparation (solution) (2) Percent weight-in-weight (percent by weight), % w/w: number of grams of a constituent (solute) in 100 g of preparation (solution) (3) Percent volume-in-volume (percent by volume), % v/v: number of millili- ters of a constituent (solute) in 100 mL of preparation (solution) (4) Milligram percent, mg%: number of milligrams of a constituent (solute) in 100 mL of preparation (solution) 15 9 Example 1: If 4 g of sucrose are dissolved in enough water to make 250 mL of solution, what is the concentration in terms of % w/v of the solution? By the method of proportion: 4g Xg = 250 mL 100 mL Solving for X, we get: X = (100 × 4) 250 = 1.6 g answer: 1.6 g in 100 mL is 1.6% w/v Example 2: An injection contains 40 mg pentobarbital sodium in each milliliter of solution. What is the concentration in terms of % w/v of the solution? By the method of proportion: 40 mg X mg = 1 mL 100 mL Solving for X, we get: X = (100 × 40) = 4000 mg or 4 g answer: 4 g in 100 mL is 4% w/v Example 3: How many grams of zinc chloride should be used in preparing 5 L of the mouth wash containing 1/10% w/v of zinc chloride? 1/10% = 0.1% = 0.1 g in 100 mL By the method of proportion: 0.1 g Xg = 100 mL 5000 mL 16  X = (0.1 × 5000)/100 answer: = 5.0 g Practice Problems (1) A pharmacist dispenses 180 prescriptions a day. How many more pre- scriptions does he need to dispense each day to bring a 15% increase? (2) If an ophthalmic solution contains 10 mg of pilocarpine in each milliliter of solution, how many milliliters of solution would be needed to deliver 0.5 mg of pilocarpine? (3) A pharmacist prepared a solution containing 10 million units of potassium penicillin per 20 mL. How many units of potassium penicillin will a 0.50-mL solution contain? (4) A cough syrup contains 5 mg of brompheniramine maleate in each 5- mL dose. How many milligrams of brompheniramine maleate would be contained in a 120-mL container of the syrup? (5) What is the percentage strength, expressed as % w/w, of a solution prepared by dissolving 60 g of potassium chloride in 150 mL of water? (6) How many grams of antipyrine should be used in preparing 5% of a 60- mL solution of antipyrine? (7) How many milligrams of a drug should be used in preparing 5 L of a 0.01% drug solution? (8) How many liters of 2% w/v iodine tincture can be made from 108 g of iodine? (9) How many milliliters of 0.9% w/v sodium chloride solution can be made from 325 g of sodium chloride? (10) If a physician orders 25 mg of a drug for a patient, how many milliliters of a 2.5% w/v solution of the drug should be used? DILUTION AND CONCENTRATION When ratio strengths are provided, convert them to percentage strengths and then set up a proportion. When proportional parts are used in a dosage calculation, reduce them to lowest terms. When a solution of a given strength is diluted, its strength will be reduced. For example, a 100 mL of a solution containing 10 g of a substance has a strength of 1:10 or 10% w/v. If this solution is diluted to 200 mL, i.e., the volume of the solution is doubled by adding 100 mL of solvent, the original strength will be reduced by one-half to 1:20 or 5% w/v. 17 9  To calculate the strength of a solution prepared by diluting a solution of known quantity and strength, a proportion may be set up as follows: Q1 ×C1 =Q2 × C2 where Q1 = known quantity C1 = known concentration Q2 = final quantity after dilution C2 = final concentration after dilution From this expression, strength or final concentration of the solution can be determined. To calculate the volume of solution of desired strength that can be made by diluting a known quantity of a solution, similar expression is used. Example 1: If 5 mL of a 20% w/v aqueous solution of furosemide is diluted to 10 mL, what will be the final strength of furosemide? 5 (mL) × 20 (% w/v) = 10 (mL) × X (% w/v) X = 5 × 20/10 = 10% w/v Example 2: If phenobarbital elixir containing 4% w/v phenobarbital is evaporated to 90% of its volume, what is the strength of phenobarbital in the remaining product? 100 (mL) × 4 (% w/v) = 90 (mL) × X (% w/v) X = 400/90 = 4.44% w/v Example 3: How many milliliters of a 0.01:20 v/v solution of methyl salicylate in alcohol can be made from 100 mL of 2% v/v solution? 0.01:20 = 0.01/20 = 0.0005 = 0.05% 100 (mL) × 2 (% v/v) = X (mL) × 0.05 (% v/v) 18  X = 200/0.05 = 4000 mL For very dilute solutions, concentration may be expressed in parts per million (ppm). For example, 5 ppm corresponds to 0.0005%. Practice Problems (1) How many milliliters of a 1:50 w/v solution of ferrous sulfate should be used to prepare 1 L of a 1:400 w/v solution? (2) If 150 mL of a 20% w/v chlorobutanol are diluted to 5 gallons, what will be the percentage strength of the dilution? (3) If 200 mL of a 10% w/v solution are diluted to 2 L, what will be the percentage strength? (4) How many milliliters of water should be added to 200 mL of a 1:125 w/v solution to make a solution such that 50 mL diluted to 100 mL will provide a 1:4000 dilution? (5) How many milliliters of water should be added to 100 mL of a 1:10 w/v solution to make a solution such that 20 mL diluted to 100 mL will provide a 1:2000 dilution? (6) What is the strength of a potassium chloride solution obtained by evapo- rating 600 mL of a 10% w/v solution to 250 mL? (7) How many liters of water for injection must be added to 2 L of a 50% w/v dextrose injection to reduce the concentration to 5% w/v? (8) How many milliliters of a 0.1% w/v benzalkonium chloride solution should be used to prepare 1 L of a 1:4000 solution? (9) How many milliliters of water should be added to a liter of 1:2000 w/v solution to make a 1:5000 w/v solution? (10) How much water should be added to 1500 mL of 75% v/v ethyl alcohol to prepare a 50% v/v solution? DENSITY AND SPECIFIC GRAVITY The pharmacist often uses measurable quantities such as density and specific gravity when interconverting between weight (mass) and volume. Density Density is a derived quantity combining mass and volume. It is defined as mass per unit volume of a substance at a fixed temperature and pressure. It 19 9 is usually expressed in CGS system, i.e., as grams per cubic centimeter (g/ cm3) or simply as grams per milliliter (g/mL). In SI units, it may be expressed as kilograms per cubic meter. It may also be expressed as number of grains per fluidounce, or the number of pounds per gallon. Density may be calculated by dividing the mass of a substance by its volume. For example, if 100 mL of Lugol’s solution weighs 120 g, its density is: 120 (g) = 1.2 g/mL 100 (mL) Specific Gravity Specific gravity is the ratio of the density of a substance to the density of water, the values for both substances being determined at the same temperature or at another specified temperature. For practical purposes, it may be defined as the ratio of the mass of a substance to the mass of an equal volume of water at the similar temperature. The official pharmaceutical compendia uses 25°C to express specific gravity. Specific gravity may be calculated by dividing the mass of a given substance by the weight of an equal volume of water. For example, if 100 mL of simple syrup, NF weighs 131.3, and 100 mL of water, at the same temperature, weighs 100 g, the specific gravity of the simple syrup is: Weight of 100 mL of simple syrup Weight of 100 mL of water 131.3 = 1.313 100 Note: The values of density and specific gravity, in metric system, are numerically equal, i.e., when expressed in g/cc, the values of density and specific gravity are the same. For example, a density of 1.2 g/cc equals specific gravity of 1.2. Specific Volume Specific volume is the ratio of volume of a substance to the volume of an equal weight of another substance taken as a standard, the volumes for both substances being determined at the same temperature. Specific volume may be calculated by dividing the volume of a given mass of the substance by the volume of an equal mass of water. For example, if 20 100 g of a syrup measures 85 mL, and 100 g of water, at the same temperature, measures 100 mL, the specific volume of that syrup is: Volume of 100 g of syrup Volume of 100 g of water 85 (mL) = 0.85 100 (mL) Note: The specific gravity and specific volume are reciprocals of each other, i.e., the product of their multiplication is 1. If the specific gravity of the solution is known, interconversions between % w/v and % w/v are possible using the following expression: Percent weight-in-volume Percent weight-in-weight (% w/v) of the solution = (% w/w) of the solution Specific gravity of the solution Example 1: How many milliliters of 90% (w/w) sulfuric acid having a specific gravity of 1.788 should be used in preparing a liter of 8% (w/v) acid? 90% w/w × 1.788 = 160.92% w/v 1000 mL × 8% w/v = 160.92% w/v × X mL answer: X = 49.7 or 50 mL Example 2: A pharmacist mixes 100 mL of 35% (w/w) hydrochloric acid with enough purified water to make 400 mL. If the specific gravity of hydrochloric acid is 1.20, calculate the percentage strength (w/v) of the final solution. 100 mL × 35% (w/w) = 400 mL × X (w/w) 100 × 35 X= = 8.75% w/w 400 answer: 8.75 × 1.20 = 10.5% w/v 21 Example 3: How many milliliters of a 64% (w/w) sorbitol solution having a specific gravity 1.26, should be used in preparing a liter of a 10% (w/v) solution? 64% w/w × 1.26 = 80.64% w/v 1000 mL × 10% w/v = X mL × 80.64% w/v 1000 × 10 X= = 124 mL 80.64 answer: 124 mL Practice Problems (1) If a liter of mannitol solution weighs 1285 g, what is its specific gravity? (2) If 50 mL of glycerin weighs 135 g, what is its specific gravity? (3) The specific gravity of ethyl alcohol is 0.820. What is its specific volume? (4) If 68 g of a sulfuric acid solution measures 55.5 mL, what is its specific volume? (5) What is the weight of 15 mL of propylene glycol having a specific gravity of 1.24? (6) What is the weight, in grams, of 250 mL of iodine solution having a specific gravity of 1.28? (7) What is the volume of 50 g of potassium chloride solution with a specific gravity of 1.30? (8) What is the weight, in kilograms, of 1 gallon of dextrose solution having a specific gravity of 1.25? (9) The strength of syrup USP solution is 65% w/w and its specific gravity is 1.313. What is its concentration in % w/v? (10) How many milliliters of 36.5% w/w hydrochloric acid are needed to prepare one gallon of 25% w/v acid? The specific gravity of hydrochloric acid is 1.20. 22  CHAPTER 2 Systems of Measurement The knowledge and application of pharmaceutical and clinical calculations are essential for the practice of pharmacy and related health professions. Many calculations have been simplified by the shift from apothecary to metric system of measurements. However, a significant proportion of calculation errors occur because of simple mistakes in arithmetic. Further, the dosage forms prepared by pharmaceutical companies undergo several inspections and quality control tests. Such a luxury is almost impossible to find in a pharmacy or hospital setting. Therefore it is imperative that the health care professionals be ex- tremely careful in performing pharmaceutical and clinical calculations. In the present chapter, a brief introduction is provided for the three systems of measurement and their interconversions: T metric system T apothecary and avoirdupois systems T household system T interconversions THE METRIC SYSTEM The metric system, which is federally mandated and appears in the official listing of drugs in the United States Pharmacopoeia (USP), is a logically organized system of measurement. It was first developed by the French. The basic units multiplied or divided by 10 comprise the metric system. Therefore, a knowledge of decimals, reviewed in Chapter 1, is useful for this system. In the metric system, the three primary or fundamental units are: the meter for length, the liter for volume, and the gram for weight. In addition to these 23 basic units, the metric system includes multiples of basic units with a prefix to indicate its relationship with the basic unit. For example, a milliliter repre- sents 1/1000 or 0.001 part of a liter. A milligram represents 0.001 g and a kilogram represents 1000 times the gram. A pharmacist rarely uses the second- ary or the derived units of the metric system. Therefore, secondary units such as Joules or Newton are not included in this book. The table of measurements in Table 2.1 is very important for the pharmacists. The pharmacist should be able to perform interconversions from a micro- gram to a centigram or from a nanogram to a microgram. The following general guidelines may be helpful: (1) To prevent the mistake of overlooking a decimal point, precede the decimal point with a zero if the value is less than one, i.e., writing 0.8 g is better than.8 g. As a practical example, if a prescription is written for Dexamethasone Oral Solution.5 mg/.5 mL, one possible mistake could be dispensing 0.5 mg/5 mL solution. This under-medication to the patient would most likely be avoided if 0.5 mg/0.5 mL is written. (2) To convert milligram (large unit) to microgram (small unit), multiply by 1000 or move the decimal point three places to the right. (3) To convert microgram (small unit) to centigram (large unit), divide by 10,000 or simply move the decimal point four places to the left. (4) To add, subtract, multiply or divide different metric units, first convert all the units to the same denomination. For example, to subtract 54 mg from 0.28 g, solve as 280 mg − 54 mg = 226 mg. Note: T Gram is represented by g or G whereas a grain is represented by gr. T Milliliters are sometimes represented by cc, which is a cubic centimeter (cm 3). This is very useful, especially when a conversion from a volume unit to a length unit or vice versa is needed. T g can also be represented by mcg. As an example, Cytotec ®, which contains the drug misoprostol, is available in strengths of 100 mcg and 200 mcg. TABLE 2.1. Metric Weights. 0.001 kilogram (kg) = 1 gram (g) 0.01 hectogram (hg) = 1 gram (g) 0.1 dekagram (dkg) = 1 gram (g) 10 decigram (dg) = 1 gram (g) 100 centigram (cg) = 1 gram (g) 1000 milligram (mg) = 1 gram (g) 1,000,000 microgram ( g) = 1 gram (g) 1,000,000,000 nanogram (ng) = 1 gram (g) 24  TABLE 2.2. Metric Volume. 0.001 kiloliter (kL) = 1 liter (L) 0.01 hectoliter (hL) = 1 liter (L) 0.1 dekaliter (dkL) = 1 liter (L) 10 deciliter (dL) = 1 liter (L) 100 centiliter (cL) = 1 liter (L) 1000 milliliter (mL) = 1 liter (L) 1,000,000 microliter ( L) = 1 liter (L) 1,000,000,000 nanoliter (nL) = 1 liter (L) (5) One should be careful with decimal points on prescriptions. When re- cording a prescription by telephone, decimal points should not be used unless needed. For example, Norpramine® 10.0 mg could be mistaken for Norpramine® 100 mg. The excess drug may cause adverse reactions such as blurred vision, confusion, flushing, fainting, etc., in the patients. The above rules can be similarly applied to the conversions of volume and length measurements. While the weight and volume measurements are the most commonly used, the measure of length is used in measurements such as the patient’s height and body surface area. The liquid and length measures are provided in Tables 2.2 and 2.3. Example 1: If a chlorpheniramine maleate tablet weighs 0.26 gram, one-fourth of the same tablet weighs how many milligrams? Since the answer is required in milligrams, convert the weight of the tablet into milligrams first. 0.26 g = 0.26 × 1000 = 260 mg 1/4 × 260 mg = 65 mg answer: 65 mg TABLE 2.3. Metric Length. 0.001 kilometer (km) = 1 meter (m) 0.01 hectometer (hm) = 1 meter (m) 0.1 dekameter (dkm) = 1 meter (m) 10 decimeter (dm) = 1 meter (m) 100 centimeter (cm) = 1 meter (m) 1000 millimeter (mm) = 1 meter (m) 1,000,000 micrometer ( m) = 1 meter (m) 1,000,000,000 nanometer (nm) = 1 meter (m) 25 Example 2: If a vial of gentamycin contains 80 mg of drug in 2 mL, how many micrograms of the drug are present in 0.025 mL? 80 mg = 80,000 g By the method of proportion, if 80,000 g are contained in 2 mL, how many micrograms are contained in 0.025 mL? 2 mL/80,000 = 0.025 mL/X answer: X = 1000 g Example 3: Add 1.25 g, 35 mg, and 80 g, and express the result in milligrams. Convert all the units to the same denomination and then perform the compu- tation. 1.25 g = 1250 mg, and 80 g = 0.08 mg Therefore, 1250 + 35 + 0.08 = 1285.08 mg answer: 1285.08 mg Practice Problems (1) 30 g of Bactroban ® ointment contains 2% mupirocin. If one gram of the ointment is applied to an affected area, how many milligrams of mupi- rocin is used? (2) Pediaprofen ® pediatric suspension contains 80 mg of ibuprofen in 5 mL of the suspension. While taking 2.5 mL of this medication, the patient spilled 0.5 mL of the suspension. How many grams of ibuprofen did the patient receive? (3) Diprosone® lotion contains 0.05% betamethasone diproprionate. How many microliters of the lotion will contain 2.5 g of the drug? (4) Fer-In-Sol® drops contain 75 mg of ferrous sulfate in 0.6 mL of the solution. If a pharmacist dispensed 90 mL of the solution, how many grams of ferrous sulfate was dispensed? (5) Feldene® tablets contain 20 mg of piroxicam per tablet. If 20 dekagrams of piroxicam is provided, how many tablets can be prepared with this amount? 26  (6) When an intravenous solution containing 0.2 g of a sulfa drug in 1 L of the solution is administered to a patient at the rate of 100 mL per hour, how many micrograms of the drug will the patient receive in a two- minute period? (7) When dividing 0.32 g of a drug into 800 equal doses, how many g of the drug will be present in each dose? (8) The four ingredients of a chewable tablet weigh 0.3 g, 115 mg, 5000 g, and 0.003 kg. How many milligrams will the tablet weigh? (9) If 200 L, 0.4 mL, 0.006 cL, and 0.0008 dL of a preservative solution are removed from a container, how many milliliters of the solution have been removed? (10) The following amounts of alcohol have been removed from a stock bottle containing 1.5 L: 0.00005 kL, 50 mL, 0.05 dkL, and 5 dL. How much alcohol will be left in the original stock bottle? APOTHECARIES’ SYSTEM Unlike the metric system which has units for weight, volume, and length, the apothecaries’ system has units for weight and volume only. This is an old system and its use is rapidly declining. However, some physicians still pre- scribe using this system. A few drug labels that were originally produced under the apothecaries’ system, still state the apothecaries’ equivalent on the label. As a few examples, phenobarbital, aspirin, codeine, sodium bicarbonate, and potassium iodide labels appear in the metric as well as apothecary units. Moreover, a few questions have also appeared in the apothecaries’ units in pharmacist licensing examinations. Therefore, pharmacists are still required to learn this system. The basic unit for weight is grain (gr) and that of volume is minim (m). Unlike the metric units, the amount is expressed in Roman numerals after the apothecaries’ symbol. For example, 1⁄2 grain is expressed as gr ss but not 1 ⁄2 gr. Twenty minims is expressed as m xx. Sometimes physicians also use Arabic numerals in the apothecary system. For example 12 ounces can be written as XII or 4 ounces as 4. Tables 2.4 and 2.5 show the relationships TABLE 2.4. Apothecaries’ Liquid Measures. 60 minims (m) = 1 fluid dram (f ) 8 fluid drams (f ) = 1 fluid ounce (f ) 16 fluid ounces (f ) = 1 pint (pt or O) 2 pints (O) = 1 quart (qt) 4 quarts (qt) = 1 gallon (gal or C) 27  TABLE 2.5. Apothecaries’ Weight Measures. 20 grains = 1 scruple ( ) 3 scruples = 1 dram ( ) 8 drams ( ) = 1 ounce ( ) 12 ounces ( ) = 1 pound (lb) 1 pound (lb) = 5760 grains (gr) between measures of liquid volume and solid weight in the apothecaries’ system. Example 1: If a prescription calls for gr ii thyroid desiccated tablets and the pharmacist has gr ss tablets in stock, how many tablets of gr ss should be provided? gr ii = 2 grains gr ss = 1⁄2 grain 2 ⁄2 = 4 tablets of gr ss 1 answer: 4 tablets of gr ss Example 2: How many doses of iv are present in O iiss of Maalox®? O iiss = 21⁄2 pints = 2.5 × 16 ounces = 40 ounces = 40 × 8 = 320 fluidrams = 320/4 = 80 doses answer: 80 doses Example 3: A doctor ordered morphine sulfate gr 2/5 and the pharmacist has a stock solution of gr 1/8 per milliliter of morphine sulfate. How many milliliters of the stock solution is required to fill the prescription? 28  gr 2/5 = 0.4 grains needed gr 1/8 = 0.125 grains per mL 0.125/mL = 0.4/X X = 0.4/0.125 = 3.2 answer: 3.2 mL of the stock solution Practice Problems (1) If two quarts of acetaminophen elixir are present in the inventory, how many f iv prescriptions can be filled? (2) If you fill approximately twelve prescriptions of f -vi Ventolin ® syrup per day, how many gallons of the syrup would be used in fifteen days? (3) How many minims of a topical keratolytic solution are contained in a 4 fluidram bottle? (4) If thirty-six APAP suppositories of 2 gr each are dispensed, how many scruples of drug are dispensed? (5) How many apothecary ounces are present in lbs iiiss? (6) How many fluidrams remain after 4 fluidrams, 60 minims, and 1⁄2 fluid- ounce of guaifenesin are removed from a one pint container? (7) How many ounces are present in gr CXX? (8) A prescription requires gr 1/200 of a drug. If a pharmacist has gr 1/100 scored-tablets, how many tablets should be dispensed? (9) If a generic syrup costs $14 for 1⁄2 oz (apoth) and the brand syrup costs $32 for the same amount of syrup, what is the dollar difference for one gallon of the drug? (10) The container for Seconal ® sodium capsules shows a strength of 100 mg (11⁄2 gr) of the drug secobarbital sodium. If an ounce of drug is available, how many capsules can be prepared? THE AVOIRDUPOIS SYSTEM The avoirdupois system is also an old system used by the pharmacist, in the past, for ordering bulk chemicals. Since this system is no longer used, practice problems on this topic will not be provided. However, for reference considerations, the following conversions of avoirdupois weights are provided: 29  1 ounce (oz) = 437.5 grains 1 pound (lb) = 7000 grains THE HOUSEHOLD SYSTEM Though inaccurate, the use of the household system of measurements is on the rise because of an increased home health care delivery. In this system, the patients use household measuring devices such as the teaspoon, dessertspoon, tablespoon, wine-glass, coffee cup, etc. In the past, a drop has been used as an equivalent of a minim. But such a measure should be discouraged because of many factors affecting the drop size which include the density of the medication, temperature, surface tension, diameter and opening of the dropper, and the angle of the dropper. The official medicinal dropper (USP-NF) has an external diameter of 3 mm, and delivers 20 drops per mL of water at 25°C. Some manufacturers provide specially calibrated droppers with their products. A few examples of medications containing droppers include Tylenol ® pediatric drops, Advil ® pediatric drops, and Neosynephrine® nasal drops. Several ear, nose, and eye medications are now available in calibrated containers which provide drops by gently pressing the containers. Sometimes, the health care professonal has to calibrate the dropper for measuring small quantities such as 0.1 mL or 0.15 mL, when the calibrated dropper is not supplied by the manufacturer. The calibration procedure is outlined in the following section. Calibration of the Medicinal Dropper A dropper is calibrated by counting the number of drops required to transfer 2 mL of the intended liquid from its original container to a 5-mL measuring cylinder. For example, if it takes 40 drops to measure 2 mL of a liquid, then the number of drops to measure 0.15 mL of the liquid is obtained by the method of proportion as follows: 40 drops/2 mL = X drops/0.15 X = 3 drops answer: 3 drops The household measures are shown in Table 2.6. It is important to remember that the household system of measurement should not be used for calculations in compounding or conversions from one system to the other. Household system of measures is designed for the 30  TABLE 2.6. Household Measures. 1 teaspoonful* (tsp) = 5 mL 1 dessertspoonful (dssp) = 8 mL 1 tablespoonful (tbsp) = 15 mL 1 ounce = 2 tbsp or 30 mL 1 wine-glass = 1 ounce 1 coffee cup = 6 fluidounces 1 glass = 8 fluidounces 1 quart (qt) = 1 liter * Some physicians denote this by. If this symbol appears in the direc- tions for patient, it is equivalent to 5 mL. If the symbol appears in the compounding or the enlargement/reduction of formulae, it is equivalent to 3.69 mL by the apothecary measure. convenience to the patient. Therefore this system is used for the directions on labels for the patients. Example 1: Suprax® suspension contains 100 mg/5 mL of the drug cefixime. If the patient takes one teaspoonful of the suspension twice daily for ten days, how many grams of the drug does the patient consume? 5 mL × 2 = 10 mL daily 10 × 10 = 100 mL, total dose 0.1 g/5 mL = X g/100 X=2g answer: 2 g Example 2: In calibrating a medicinal dropper, 2 mL of a pediatric solution resulted in 48 drops. If it is desired to administer 0.08 mL of the medication to a baby, approximately how many drops should be given? By the method of proportion: 48 drops/2 mL = X drops/0.08 mL X = 1.922 or 2 drops answer: 2 drops 31 Example 3: If a teaspoonful of Tussi-Organidin ® syrup is to be given three times daily for five days, how many fluidounces of the medication should be dispensed? 5 × 3 = 15 mL daily 15 × 5 = 75 mL or 21⁄2 fluidounces answer: 21⁄2 fluidounces Practice Problems (1) A pharmacist dispensed 4 fluidounces of an antacid suspension with instructions that the patient take two tablespoonfuls of the medication four times a day. How long will the medication last? (2) Children’s Advil ® is available in a suspension form containing ibuprofen in a strength of 100 mg/5 mL of the suspension. If the patient receives one teaspoonful of the medication three times daily, how many grams of the drug will be consumed by the patient in two days? (3) It is required to administer 0.3 mL of an otic solution using a new medicinal dropper. How many drops of the solution is to be administered when it is determined that 45 drops measure 2 mL of the otic solution? (4) For a patient suffering from diarrhea, a doctor advised the patient to take one glassful of an electrolyte solution three times a day. The patient took one coffee-cupful of medication three times for one day. How much extra medication was the patient supposed to take? (5) If a patient needs one teaspoonful of Alupent® oral liquid three times a day for ten days, how many fluidounces of medication should the pharmacist dispense? (6) A patient received 8 fluidounces of Kaopectate® with the instructions of taking two teaspoonfuls of medication after each bowel movement. If the patient took Kaopectate® after ten such bowel movements, how many milliliters of the medication should be left in the container? (7) A child received 5 f of amoxicillin suspension containing 125 mg/5 mL. If one teaspoonful was taken three times a day, how many grams of amoxicillin did the child take in one week? (8) How many teaspoonfuls equal the volume of a coffee cup? (9) Is it true that one-half tablespoon equals one teaspoon? (10) If a prescription is required for Phenergan VC with Codeine, two tea- spoonfuls at bedtime for fifteen days, how many fluidounces of the syrup would the pharmacist dispense? 32  TABLE 2.7. Conversion Equivalents of the Measurement Systems. Apothecar y Metric Household 1 minim (m) 0.06 mL — 16.23 m 1 mL — 1 fluidram (f ) 3.69 mL 1 teaspoonful or 5 mL 1/2 fluidounce (f ) 15 mL 1 tablespoonful 1 f 29.57 mL 2 tablespoonfuls 1 pint (O) 473 mL 500 mL 1 quart (qt) 946 mL 1 liter INTERCONVERSIONS In a pharmaceutical or clinical setting, health care professionals encounter more than one system of measurement. Therefore, it becomes necessary to convert all quantities to the same system of measurement. Depending upon the circumstances and the degree of accuracy required, a particular system would be preferred over the others. Some commonly used equivalents in pharmacy practice are shown in Tables 2.7 and 2.8. A pharmacy or health care institution may use a particular set of equivalents as their established standards for interconversion. The health care professionals working in that environment must use those standards. If such standards are TABLE 2.8. Approximate Equivalents Used by Health Professionals. Commonly Ap othecary Metric Used Equivalent 1 grain (gr) 64.8 mg 65 mg* 1 ounce ( ) 31.1 g 30 g 1 pound 373.2 g 454 g** 1 minim 0.062 mL 0.06 mL 1 fluidounce 29.57 mL 30 mL 128 f 3785 mL 1 gallon (C) — 1 kg 2.2 lb * It should be remembered that this conversion is only approximate. Several other approximations have been used on the labels of certain tablets. For example. Saccharin tablets from Eli Lilly Company shows 1⁄2 gr (32 mg) on its label whereas the 1 phenobarbital tablets from the same company have 30 mg ( ⁄2 gr) on its label. Similarly sodium bicarbonate tablets from Eli Lilly have 5 grs (325 mg) on its label and potassium iodide from the same company has 300 mg (5 grs) on its container label. In the present book, it is advised to use one grain equivalent as 65 mg. ** This amount represents the equivalent of 1 avoirdupois pound. Since the pound is a bulk quantity, use of the avoirdupois system of measurements unit is more common. 33 not established, generally, the equivalents shown in the right column of Table 2.8 may be used. Example 1: Accupril ® tablets are available in strengths of 5 mg and 40 mg of the drug quinapril HCl. Express these strengths in grains. 65 mg/l grain = 5/X X = 0.076 or 1/13 grains 65 mg/l grain = 40/X X = 0.62 = 1/1.6 = 5/8 grains answer: The range of available Accupril ® tablets in grains is 1/13 to 5/8. Example 2: Daypro®, a nonsteroidal antiinflammatory agent, has a maximum daily dose requirement of 26 mg/kg/day. What is the maximum number of Daypro® 600 mg tablets that can be given to a 127-lb patient? 26 mg/2.2 lbs = X mg/127 lb X = 1501 mg 600 mg/1 tab = 1501 mg/X X = 2.5 tablets answer: 2.5 tablets Example 3: Tylenol with codeine® elixir contains 12 mg of codeine per 5 mL of the elixir. If a pharmacist dispenses 4 fluidounces of the elixir to a patient, how many grains of codeine does the patient receive? 12 mg/5 mL = X/120 mL X = 288 mg 34  65 mg/1 gr = 288 mg/X X = 4.43 grains answer: 4.43 grains Practice Problems (1) A Halcion ® tablet contains 0.25 mg of triazolam. How many grains of the drug triazolam would be present in 100 tablets of Halcion ®? (2) If a quart of suspension contains 2 g of a drug, how many grains would be present in a gallon of the suspension? (3) A Carafate® tablet contains 1 g of sucralfate. How many ounces of sucralfate would be present in ten Carafate® tablets? (4) How many Hismanal® tablets (5 mg) would contain an ounce of astem- izole? (5) A prescription requires gr ii of phenolphthalein in f iv of an emulsion. If the patient takes 2 tbsp of the emulsion at bedtime, how many milli- grams of phenolphthalein does this dose represent? (6) If a prescription requires ii of camphor for ii of an ointment, how many grams of camphor are needed to prepare a pound of the ointment? (7) Zovirax® tablets, containing the antiviral drug acyclovir, are usually given in a dose of 80 mg/kg/day for five days for treating chickenpox. If the patient weighs 165 lb, how many ounce(s) of acyclovir would the patient consume if he has to take the full dose prescribed? (8) If a physician prescribes 11⁄2 grains of phenobarbital sodium from the Eli Lilly Company, how many grams of drug would it contain? (9) Mr. John Doe has been suffering from diarrhea and Dr. Brown wants him to take 30 mL of Kaopectate®. How many tablespoonfuls of Kaopectate® should Mr. Doe take? (10) Mrs. Straker has been advised by her physician to take at least 1.2 L of an electrolyte solution per day. How many glassfuls of the electrolyte solution should she take per day? 35  CHAPTER 3 Prescription and Medication Orders The interpretation of prescription medication orders is one of the most important requirements of professional pharmacy practice. According to the National Association of Boards of Pharmacy’s (NABP’s) Model State Phar- macy Act, The ‘‘Practice of Pharmacy’’ shall mean the interpretation and evaluation of prescription orders; the compounding, dispensing, labelling of drugs and devices (except labeling by a manufacturer, packer, or distributor of Non-Prescription Drugs and commercially packaged legend drugs and devices); the participation in drug selection and drug utilization reviews; the proper and safe storage of drugs and devices and the maintenance of proper records, therefore; the responsibility of advising where necessary or where regulated, of therapeutic values, content, hazards and use of drugs and devices; and the offering or performing of those acts, services, operations or transactions necessary in the conduct, operation, management and control of pharmacy. The Model State Pharmacy Act of the NABP also defines drugs which are to be dispensed with or without prescription. ‘‘Prescription Drug or Legend Drug’’ shall mean a drug which, under Federal Law is required, prior to being dispensed or delivered, to be labeled with either of the following statements: (1) ‘‘Caution: Federal law prohibits dispensing without prescription’’ (2) ‘‘Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian’’; or a drug which is required by any applicable Federal or State Law or regulation to be dispensed on prescription only or is restricted to use by practitioners only. Non-prescription drugs are defined as ‘‘Non-narcotic medicines or drugs which may be sold without a prescription and which are prepackaged for use by the 37 consumer and labelled in accordance with the requirements of the statutes and regulation of this State and the Federal Government.’’ The definitions provided above underscore the importance of understanding and interpreting prescriptions. A prescription is defined as an order for medica- tion from a doctor, dentist, veterinarian, or any other licensed health care professional authorized to prescribe in that state. It shows the relationship between the prescriber, patient, and the pharmacist, in which the latter provides the medication to the patient. TYPES OF PRESCRIPTIONS Pharmacists receive prescriptions by telephone, fax, as written prescriptions from individual prescribers, practicing in a group, or hospitals and other institutions. Telephone orders are reduced to a written prescription (hard copy) by pharmacists. Generally, prescriptions include printed forms called ‘‘prescription blanks’’ which include the name, address, and telephone number of the prescriber; a provision to write the name, address, age or date of birth of the patient; and the symbol. ‘‘Medication orders’’ are prescription equivalents which are written by practitioners (prescribers) in a hospital or a similar institution. Components of medication orders with appropriate exam- ples are presented in the subsequent section. COMPONENTS OF PRESCRIPTIONS Generally, a prescription consists of the following parts (see the sample prescription in Figure 3.1): (1) Prescriber’s name, degree, address and telephone number. In the case of prescriptions coming from a hospital or a multicenter clinic, the hospital or clinic’s name, address and telephone numbers appear at the top. In such a case, the physician’s name and degree would appear near his/her signature. (2) Patient’s name, address, age, and the date of prescription. (3) The Superscription, which is represented by the Latin sign.. This sign represents ‘‘take thou’’ or ‘‘you take’’ or ‘‘recipe.’’ Sometimes, this sign is also used to denote the pharmacy itself. (4) The Inscription is the general content of the prescription. It states the name and strength of the medication, either as its brand (proprietary) or generic (nonproprietary) name. In the case of compounded prescriptions, the inscription states the name and strength of active ingredients. 38  FIGURE 3.1. Sample prescri pti on. (5) The Subscription represents the directions to the dispenser and indicates the type of dosage form or the number of dosage units. For compounded prescriptions, the subscription is written using English or Latin abbrevia- tions. A few examples are provided as follows: T M. et ft. sol. Dispvi (Mix and make solution. Dispense six fluidounces) T Ft. ung. Disp ii (Make ointment and dispense two ounces) T Ft. cap. DTD xii (Make capsules and let twelve such doses be given) (6) The Signa, also known as transcription represents the directions to the patient. These directions are written in English or Latin or a combination of both. Latin directions in prescriptions are declining, but since they are still used, it is important to learn them. A few examples are provided below: 39  T ii caps bid, 7 days (Take two capsules twice daily for seven days) T gtt. iii a.u. hs (Instill three drops in both the ears at bedtime) T In rect. prn pain (Insert rectally as needed for pain) (7) The prescriber’s signature. (8) The refill directions, in which the information about how many times, if authorized, a prescription can be refilled is provided. (9) Other information, such as ‘‘Dispense as Written.’’ (10) Drug Enforcement Administration (DEA) registration number and/or the state registration number of the prescribing authority. LABEL ON THE CONTAINER It is a legal requirement to affix a prescription label on the immediate container of prescription medications. The pharmacist is responsible for the accuracy of the label. It should bear the name, address, and the telephone number of the pharmacy, the date of dispensing, the prescription number, the prescriber’s name, the name and address of the patient, and the directions for use of the medication. Some states require additional information. The name and strength of the medication, and the refill directions are also written frequently. The label for a sample prescription is in Figure 3.2. MEDICATION ORDER While prescriptions are written in an outpatient setting, medication orders FIGURE 3.2. Sample label. 40  FIGURE 3.3. Sample medication order. (Figure 3.3) are written in an institutional setting. A medication order is also known as a drug order or a physician’s order. These orders generally contain the name, age or date of birth, hospital ID number, room number, the date of admission to hospital, and any patient allergies. Sometimes the patient’s diagnosis is included. Besides patient information, the following information about the medication is included: T date and time of the medication order T name of the drug (brand or generic) T dosage form T route of administration, e.g., oral, sublingual, intramuscular, intravenous, rectal, etc. T administration schedule, e.g., times per day, milliliters per hour, at bedtime, etc. T other information such as some restrictions or specifications T prescriber’s signature T provision for the pharmacist’s or nurse’s notes 41 COMMON LATIN TERMS AND ABBREVIATIONS Terms Related to Quantities Abbreviation Term/Phrase Meaning aa Ana Of each q.s. Quantum sufficiat Sufficient quantity ad lib. Ad libitum Freely, at pleasure Ounce One ounce f Fluidounce One fluidounce O or pt Pint One pint qt Quart One quart gal Gallon One gallon m Minim One minim Dram or drachm One drachm f Fluid drachm One fluid drachm gr Grain One grain Scruple One scruple Terms Related to Administration Times Abbreviation Term/Phrase Meaning qd Quaque die Once daily bid Bis in die Twice daily tid Ter in die Three times daily qid Quarter in die Four times daily am or AM Ante meridium In the morning pm or PM Post meridium In the evening h.s. Hora somni At bedtime a.c. Ante cibos Before meals p.c. Post cibos After meals i.c. Inter cibos Between meals om Omne mane Every morning on Omne nocte Every night p.r.n. Pro re nata When required q.h. Quaque hora Every hour q2h Quaque secunda hora Every two hours q3h Quaque tertia hora Every three hours q4h Quaque quarta hora Every four hours q6h Quaque sex hora Every six hours q8h Quaque octo hora Every eight hours 42 Terms Related to Preparations or Remedies Abbreviation Term/Phrase Meaning amp Ampul Ampul aq Aqua Water aur or oto Auristillae Ear drops cap Capsula A capsule comp Compositus Compounded cm or crem Cremor A cream garg gargarisma Gargle gtt Guttae Drops inj. Injectio An injection liq. Liquor A solution mist. Mistura A mixture Neb. Nebula A nebulizer pil. Pilula A pill pulv. Pulvis A powder suppos. Suppositorium A suppository troch. Trochiscus A lozenge Instructions for Preparations Abbreviation Term/Phrase Meaning div. Divide Divide ft Fiat Let it be made m. ft. Misce fiat Mix to make d.t.d. dentur tales doses Such doses be given e.m.p. ex modo prescriptio In the manner prescribed s sine Without Method of Application Abbreviation Term/Phrase Meaning o.d. or OD Oculus dexter Right eye o.l. or OL Oculus Laevus Left eye o.u. or O2 Oculo utro Each eye or both eyes o.s. or OS Oculo sinister Left eye a.d. or AD Aurio dextra Right ear a.l. or AL Aurio Laeva Left ear e.m.p. Ex. modo-prescriptio As directed u.d. Ut. dictum As directed c Cum With dext Dexter Right 43 Names for Ingredients and Products Common Names Meaning Acidi tannici Tannic acid Ac. Sal. Salicylic acid Ac. Sal. Ac. Aspirin Aq. hamamelis Witch hazel Burrow’s solution Aluminum acetate solution Camphorated oil Camphor liniment Camphorated Tr of opium Paregoric Cocoa butter Theobroma oil Epsom salt Magnesium sulfate Hydrous wool fat Lanolin L.C.D. Liquid coal tar solution Liq. calcis Lime water Lugol’s solution Strong iodine solution Methylrosaniline Cl Gentian violet Olei lini Linseed oil Oleum ricini Castor oil Oleum morrhuae Cod liver oil Pulv. amyli Starch S.V.R. Alcohol USP Sweet oil Olive oil Whitfield’s ont. Benzoic and salicylic acids ointment Miscellaneous Abbreviation Meaning AA Apply to affected area AUD Apply as directed ASA Acetyl salicylic acid APAP Acetaminophen BCP Birth control pills BIW Twice a week BM Bowel movement BP Blood pressure BS Blood sugar BSA Body surface area ć With CHF Congestive heart failure DSS Doccusate 44  EES Erythromycin ethyl succinate et and fl Fluid FA Folic acid HA Headache HC Hydrocortisone HCTZ Hydrochlorothiazide HT Hypertension ID Intradermal IM Intramuscular INH Isoniazid IOP Intraocular pressure IV Intravenous IVP Intravenous push IVPB Intravenous piggy bag MVI Multivitamin infusion MOM Milk of magnesia N&V Nausea and vomiting NR Nonrepeatable or no refill NTG Nitroglycerin PBZ Pyribenzamine PPA Phenylpropanolamine SOB Shortness of breath SC Subcutaneous SL Sublingual tal. dos Such doses TIW Thrice a week TPN Total parenteral nutrition URI Upper respiratory infection UTI Urinary tract infection Vehicles Abbreviation Meaning aq. bull Boiling water DW/or aq. dist Distilled water D5W Dextrose 5% in water NS or NSS Normal saline (10.9% sodium chloride) ⁄2NS 1 Half strength of normal saline RL Ringer’s lactate 45  MEDICATIONS AND THEIR DIRECTIONS FOR USE The following medications represent the most frequently prescribed dosage forms and their commonly prescribed signa. While the dosage forms may be available in several strengths, only one strength is listed here. The generic names of drugs are provided in parentheses. When the most frequently pre- scribed drug is generic, the brand name is provided in parentheses. T Accupril® 5 mg (quinapril HCl): One tab qd T Aciphex® 20 mg (rabeprazole sodium): One tab qd T Actos® 7.5-45 mg (pioglitazone HCL): One tab qd T Adalat® CC 60 mg (nifedipine): One tab Qd, ac T Advil® (ibuprofen) Children’s Suspension: tsp-iid T Aldactone® 50 mg (spironolactone): One tab Qd T Aldoril® 25 (methyldopa + HCTZ): One tab bid T Allegra® 60 mg (Fexoferadine HCl): One cap bid T Allopurinol 100 mg (Zyloprim ®): One tab tid. pc. T Alupent® Inhaler (metaproterenol sulfate): 2–3 puffs q 3–4 h T Alupent® Syrup (metaproterenol sulfate): tsp-ii tid. ac T Ambien ® 5 mg (zolpidem tartrate): 2 tabs qd. hs T Amoxil® 125 mg 5 mL (amoxicillin): tsp tid 7 days T Anaprox DS® (naproxen sodium): One tab, bid. pc T Antivert® 25 mg (meclizine HCl): One tab Qd, one hour prior to travel T Aspirin 325 mg: 2 tabs qid. prn pain T Atarax® 50 mg (hydroxyeine HCl): i tab, qid T Ativan ® 1 mg (lorazepam): tid. 1–2 tabs T Atrovent® Inhaler tipratoprium bromide: 1–2 tabs inhalations qid. ud T Augmentin ® 125 mg/5 mL (amoxicillin clauvinate): One tsp tid. 7 days T Avalide 150-300 mg (irbesartan/12.5 mg HCTZ): One tab qd ® T Avandia® 4-8 mg (rosiglitazone maleate): One tab qd (8 mg) or bid (4 mg) T Axid® 300 mg (nizatidine): iqhs T Azmacort® Inhaler (triamcinolone acetonide): 1–2 inhalations tid.-qid T Bactrim® DS sulfamethoxazole trimethoprim): One tab bid. 10 days T Bactroban ® (mupirocin): Apply tid. (or Atid) T BCP (estrogen + progestin): One tab qd. ud T Beclovent ® (beclomethasone dipropionate): One puffs-ii. qid. ud T Beconase® (beclomethasone dipropionate): 2 inhalations in each nostril, bid T Bentyl ® 20 mg (dicyclomine HCl): One tab bid. ac T Betoptic® (betaxolol HCl): gtt-ii ou bid. Ud 46 T Biaxin ® 250 mg (clarithromycin): One tab ql2h. 7–14 days T Blocadren ® 10 mg (timolol maleate): One tab qd. prn migraine T Brethaire® (terbutaline sulfate): puffs-ii q 4–6 h T Bumex® 1 mg (bumetanide): One tab qd T Buspar ® 5 mg (buspirone HCl): One tab tid. T Calan SR® 240 mg (verapamil HCl): One tab qd T Capoten ® 50 mg (captopril): tab-ss bid star, i tid. ld T Carafate® Suspension (sucralfate): tsp-ii qid. 4 weeks T Cardene® 30 mg (nicardipine HCl): One cap tid. ic T Cardizem® 30 mg (diltiazem HCl): One tab qid T Cardura® 4 mg (doxazocin mesylate): One tab qd T Cartia-XT® 120-300 mg (diltiazem HCl): One tab qd T Cartrol® 5 mg (carteolol HCl): One tab qd star. ii-qd T Cataflam® 50 mg (diclofenac potassium): I tablet, tid. T Catapress TTS®-2 Patch (clonidine HCl: Apply to upper arm or chest. q7d. ud T Ceclor ® 250 mg (cefaclor): One cap q8h. finish all T Ceftin ® 250 mg (cefuroxime axetil): One tab bid. finish all.pc T Cefzil® Suspension 125 mg/5 mL (cefprozil): tsp-i bid. 10 days T Celebrex® 100-200 mg (celecoxib): One cap bid (100 mg)/one cap qd (200 mg) T Celexa® 20-40 mg (citalopram hydrobromide): One tab qd T Chlordiazepoxide 10 mg (Librium ®): One tab tid. pc T Cipro® 500 mg (ciprofloxacin HCl): One tab ql2h. 14 days.ac T Claritin ® 10 mg (loratadine): One tab qd. ac T Cleocin-T® Topical Solution (clindamycin HCl): AA tid. UD T Clinoril® 200 mg (sulindac): One tab bid. pc. 10 days T Clonidine® 0.2 mg (Catapress ® ): One tab, bid T Clozaril® 25 mg (clozapine): 2 tabs, bid T Cogentin ® 1 mg (benztropine mesylate): 2 tabs qd T Compazine® Suppositories 25 mg (prochlorperazine): In rect bid T Corgard® 80 mg (nadolol): 2 qd T Cortisporin Otic® Solution (neomycin, polymyxin and hydrocortisone): gtt-iv au qid, UD T Coumadin ® 5 mg (warfarin sodium): i qd T Cozaar ® 25 mg (losartan potassium): 1–2 tabs qd T Cytotec® 100 mcg (misoprostol): One tab qid. pc T Dalmane® 15 mg (flurazepam HCl): caps-ii qhs T Darvocet-N 100 (apap/Propoxyphene napsylate): One tab q4h. prn pain T Daypro® (oxaprozin): ii-qd. pc T Deconamine Syrup® (cpm and pseudoephedrine): tsp-i. ud T Deltasone® 50 mg (prednisone): One tab qd. Then reduce the dose gradually as directed. 47 T Demadex® 10 mg (torsemide): i qd T Demerol® 50 mg (meperidine HCl): 2 tab, q3h. prn T Demulen ® 35 mcg/1mg (ethinyl estradiol and ethyrodiol diacetate): One tab qd, UD T Depakene® (valproic acid): 1 tab qd. pc T Depakote® 125 mg (divalproex Na): 1–2 caps tid. T Desogen ® 0.15 mg/30 mcg (desogestrel and ethinyl estradiol): One tab qd, UD T Desyrel® 150 mg (trazodone HCl): i qd T Dexamethasone Oral 2 mg (Decadron ®): I qd. om T Diabeta® 2.5 mg (glyburide): i qd. om T Diflucan ® 100 mg (fluconazole): ii stat, i qd T Dilacor ® XR 180 mg (diltiazem HCl): i qd T Dilantin ® 50 mg Infatabs (phenytoin): ss tab, tid. T Diphenhydramine HCl Syrup (Benadryl ®): tsp-i tid., and ii hs T Ditropan ® (oxybutynin cl): One tab, ac. prn pain T Dolobid® 250 mg (diflunisal): ii tid. pc T Donnatal® Extentab (PB + hyoscyamine + atropine + scopolamine): i tid. T Doral® 15 mg (quazepam): 1/2 tab, qhs T Doxepin ® 75 mg (Sinequan ®, Adapin ®): One tab qd T Doxycycline 100 mg (Vibramycin ® ): One cap bid. 10 days T Duricef® 1g (cefadroxil monohydrate): i qd. 10 days T Dyazide® (triamterene + HCTZ): 1 cap qd T Dynacirc® 5 mg (isradipine): i qd T E-Mycin ® 333 mg (erythromycin): i q8h. p.c., 7 days T EES® (erythromycin): i q6h. 7 days T Effexor ® 25 mg (verilafaxine HCl): One tab tid. T Elavil® 50 mg (amitriptyline): One tab qhs T Eldepryl® (selegiline): i bid T Elocon ® cm (mometasone furoate): AA qd T Entex® LA (phenylpropanolamine − guaifenesin): i bid T Equagesic® (meprobamate + aspirin): 2 tabs. qid. prn T Eryc® (erythromycin): i q6h. 14 days T Erythromycin 500 mg (PCE®, E-Mycin ®. Ilisone®): i q12h, 10 days T Estrace® 2 mg (estradiol): i qd. cycles of three weeks followed by a week off T Estraderm® 0.1 mg (estradiol): AUD. BIW T Eulexin ® (flutamide): 2 caps. q8h T Felbatol® (felbamate): i qid T Feldene® 20 mg caps (piroxicam): i qd. pc T Fioricet® (apap. butalbital, caffeine): 2 caps, q4h prn. pain T Fiorinal® (aspirin, butalbital. caffeine): 2 caps. q4h prn. pain T Fiorinal® with codeine: 2 caps. q4h. prn pain 48 T Flagyl® 500 mg (metronidazole): One tab tid. for 5–10 days T Flexeril® (cyclobenzaprine HCl): i tid. T Flonase™ 50 mcg per actuation (fluticasone propionate): 2 sprays in each nostril qd T Floxin ® 300 mg tabs (ofloxacin): i q12h. 14 days T Fosamax® 5 mg (alendronate Na): One tab qd T Glucophage® 500 mg (metformin HCl): One tab bid, ic T Glucotrol® 5 mg (glipizide): One tab qd T Glynase™ PresTab™ 1.5 mg (glyburide): i qd. c breakfast T Glyset® 25-100 mg (miglitol): One tab tid with the first bite of each meal T Habitrol® 14 mg (nicotine TDDS): i patch qd. 8 wks T Halcion ® 0.125 mg tabs (triazolam): 1–2 qhs T Haldol® 0.5 mg (haloperidol): One tab bid T HCTZ 25 mg tabs (Esidrix®. Hydrodiuril ® ): ii qd T HC 10 mg tabs (Cortef®): ii bid T Hismanal® tabs (astemizole): i qd T Hydralazine HCl 50 mg tabs (Apresoline ®): i qid T Hydroxyzine 50 mg tabs (Atarax®, Vistaril®): i qid T Hytrin ® 5 mg (terazocin): One tab qd T Ibuprofen 400 mg tabs (Motrin®): i qid. pc T Imdur ® 30 mg (isosorbide mononitrate): One tab qd T Imipramine 25 mg (Tofranil ® ): 2 tabs, qhs T Imitrex™ 25 mg tab and 6 mg vial (sumatriptan succinate): One tab prn migraine T Imodium ® 2 mg (loperimide HCl): ii stat, i after each BM T Inderal® 40 mg tab (propranolol HCl): i tid. T Indocin ® 50 mg tabs (indomethacin): i tid. pc T Insulin NPH (Novolin ® Ilentin ®, Humulin®): icc, qd sc T Intal® Inhaler (cromolyn sodium): inhalations-ii. qid. UD T Ionamin® 15 mg (phentermine resin): One cap ac T Isoptin ® 80 mg (verapamil HCl): i tid. T Isosorbide Dinitrate 20 mg (Isordil ®, Sorbitrate ® ): One tab, q6h T K-Dur ® 20 meq tabs (potassium chloride): ii qd T K-Lor ® oral solution (potassium bicarbonate/citrate): M in glassful of OJ and drink T K-Tab® (potassium supplement): ii bid T Keflet® 250 mg cap (cephalexin): 1–2 tabs qid, 7 days T Keflex® 500 mg caps (cephalexin): i qid. 7 days T Kerlone® 10 mg tabs (betaxolol HCl): ii qd T Klonopin ® 1 mg tab (clonazepam): ss tid. T Lamisil® 250 mg (terbinafine HCl): One qd for six weeks T Lanoxin ® 0.25 mg tabs (digoxin): ss qd T Lasix® 40 mg (furosemide): One tab qd 49 T Lescol® 20 mg cap (fluvastatin Na): One tab, qd, hs T Levaquin® 250-500 mg (levofloxacin): One tab qd T Levoxyl ® 0.125-0.200 mg (levothyroxine): One tab qd T Lidex® Ont 0.05% (fluocinomide): AA qd T Lipitor ® 10 mg (atorvastatin Ca): One tab qd T Lithionate® and Lithotabs T Lithium Carbonate 300 mg tab (Eskalith ®. Lithobid®): ii tid. T Lodine® 300 mg (Etodolac ®): One tab tid. pc T Loestrin FE® 1 mg/20 mcg/75 mg (norethindrone, ethinyl estradiol, ferrous fumarate): 1 qd T Lomotil® (diphenoxylate HCl + atropine sulfate): tsp-tid. prn diarrhea T Lopid® 600 mg (gemfibrozil): One tab bid. ac T Lopressor ® 50 mg (metoprolol tartrate): 2 tab qd T Lorabid® (loracarbet): One tab bid. ac. 7 days T Lorcet® Plus & Lorcet 10/650 T Lorelco® 250 mg (probucol): 2 tab qd T Lortab® 5/500 (apap + hydrocodone bitartrate): q4-6h, prn pain T Lotensin ® 10 mg tabs (benazepril HCl): i qd T Lotrimin ® cm 1% (clotrimazole): AA bid. UD T Lotrisone® (clotrimazole + betamethasone dipropionate): AA tid. T Lozol® 1.25 mg tab (indapamide): ii qd T Macrodantin® 50 mg tabs (Nitrofurantoin macrocrystals): i qid. 7 days T Maxair ® Autohaler (pirbuterol acetate): puffs-ii q4-6h. UD T Maxalt® 5-10 mg (rizatriptan benzoate): One tab qd (max 30 mg/24 hr) T Maxaquin® tabs (lomefloxacin HCl): i qid. 14 days T Maxzide® 25-mg (triamterene/HCTZ): 2 caps qd T Mecliziné HCl 50 mg tabs (Antivert ® ): One tab prior to travel T Meclomen ® 50 mg tabs (meclofenamate): i qid. pc T Medrol® 4 mg tab (methylprednisolone): ii qd T Mellaril® 50 mg tab (thioridazine HCl): i tid. T Meridia® 5-15 mg (sibutramine HCl): One tab qd (10 mg) T Methyldópa 250 mg tab (Aldomet®): ii bid T Metronidazole 250 mg tab (Flagyl ®): i tid. 7 days T Mevacor ® 20 mg tab (lovastatin): i qd, pm T Micro-K Ex