Dosage Calculations Study Guide PDF

GARDEN CITY UNIVERSITY COLLEGE FACULTY OF HEALTH SCIENCES DEPARTMENTS OF NURSING/MIDWIFERY PHARMACOLOGY, THERAPEUTICS AND PHARMACOVIGILANCE DOSAGE CALCULATION – STUDY GUIDE CONVERSION TABLE 1 k...

GARDEN CITY UNIVERSITY COLLEGE FACULTY OF HEALTH SCIENCES DEPARTMENTS OF NURSING/MIDWIFERY PHARMACOLOGY, THERAPEUTICS AND PHARMACOVIGILANCE DOSAGE CALCULATION – STUDY GUIDE CONVERSION TABLE 1 kilogram (kg) = 1000 grams (g) Convert kilograms to grams by Multiplying kilograms by 1,000 Convert grams to kilograms by dividing grams by 1,000 1 gram (g) = 1000 milligrams (mg) Convert Grams to Milligrams by Multiplying grams by 1,000 Convert Milligrams to grams by dividing milligrams by 1,000 1 milligram (mg) = 1000 micrograms (mcg) Convert milligrams to micrograms by Multiplying milligrams by 1,000 Convert micrograms to milligrams by dividing micrograms by 1,000 Grains (gr.) 15 = 1 Gram (g) To convert g. to gr multiply by 15 To convert gr to g divide by 15. 1 Grain (gr.) = 60 Milligrams (mg) To convert gr. to mg multiply gr. by 60 To convert mg to gr. divide mg. by 60 1 mL = 1 cc 1 ounce (oz) = 30 mL 1 tablespoon (T or tbsp) = 15 mL 1 teaspoon (t or tsp) = 5 mL 2.2 pound (lb) = 1 kg To convert pounds to kg divide pounds by 2.2 To convert kg to pounds multiply by 2.2 1 |Y. OBIRIKORANG 2 |Y. OBIRIKORANG 3 |Y. OBIRIKORANG EXAMPLES OF INCORRECT SI/METRIC USAGE CORRECT USAGE INCORRECT USAGE FOR km Km, km., KM, kms, K, k Kilometre km/h KPH, kph, kmph, km/hr kilometre per hour °C C, deg C, ° C, C° degree Celsius m M, m., mtr, mtrs Metre L, l L., l., ltr, ltrs Litre mL, ml ML, Ml, mL., ml., mls Millilitre kg KG, KG., Kg, Kg., kgr, kgs, kilo Kilogram h hr, hrs, HR, h., HR., HRS. Hour s sec, S, SEC, sec., s., S. Second mm Mm, mm., MM Millimetre m2 sq m, sqm, sq. m., sq. mtr. square metre g G, G., g., gr, gm, gms, GR, GM, GRM, grms Gram mg Mg, MG, µg mcg*, ug* Microgram cm3 cc, cu cm cubic centimetre Notes * Because the symbol “µg”, when handwritten, looks similar to “Mg” (megagram), which is often contextually interpreted as “mg” (milligram), and is therefore a frequent cause of overdoses, the abbreviation “mcg” is preferred in the medical field in the US (see the Joint Commission recommendations). For a similar reason and also the reason of being difficult to type, the symbol “ug” is sometimes used, especially in other countries, due to its similarity in appearance to “µg”. Despite their prevalence, these abbreviations are incorrect nevertheless. 4 |Y. OBIRIKORANG Explanations The spelling of metre and litre is the official one, and that of meter and liter is non-standard. In the US, the meter and liter spellings are commonly used despite their unofficial and non-standard status, even though metre and litre are just as valid and legal; the English spelling used by all other nations and international organizations (including the BIPM itself and ISO) is exclusively metre and litre. In a strict sense, spelling and pronunciation are matters of language and are not set by the international standards that define SI. However, the SI is officially published in the English and French languages, and the spelling of SI units in these languages follows the official specification. Official specification notwithstanding, rules and patterns nevertheless exist within languages which guide spelling and pronunciation. As such, in keeping with the pronunciation of the other SI units involving prefixes, which all accent the first syllable, the logically consistent and proper pronunciation of the word kilometre is KILL-oh-meet-ur, not kill-AHM-it-ur. This is similar to the word nanometre, which is pronounced NAN-oh-meet-ur, not nan-AHM-it-ur. The symbol for litre may be either an uppercase “ell” (L) or a lowercase “ell” (l); both are correct. In the US, Canada, and Australia, the uppercase “ell” (L) is preferred since it is easily distinguished with the digit one (1) and the uppercase “eye” (I), but most other nations use the lowercase “ell” (l) to adhere strictly to the standard of uppercase symbols being reserved for units derived from names of people. A list of the SI/metric units and symbols, plus more details on their use is given in USMA’s Guide to the Use of the Metric System. 5 |Y. OBIRIKORANG  CALCULATING DOSAGES There are several ways of calculating dosages. These include; Using ratios and proportions Using a formula Ratios and Proportions: Ratios are comparing 2 things. In daily life ratios are often expressed as fractions i.e.: 1 to 6 or 1/6 In terms of medicines, we use ratios to explain things like mg per tablet i.e.: 1 tablet is 10 mg, so 1 tablet 10 mg Proportions are comparing 2 ratios. The equal sign between them shows this relationship. 1 = 2 2 (is the same as) 4 With proportions you can cross multiply to find a missing value! Proportions also allow us to check our answer by cross multiplying. The answer on both sides after cross multiplying should be the same! Example: A doctor’s order reads: Phenobarbital 100 mg elixir PO a day. On hand: Phenobarbital 20 mg/5 mL. How much Phenobarbital will you administer? Solution Set up what we know… In words “20 mg is to 5 mL as 100 mg is to X mL (the unknown) The proportion: 20 mg = 100 mg 5 mL X mL Cross Multiply (20 mg) x (X mL) = (5 mL) x (100 mg) You are left with 20X = 500 6 |Y. OBIRIKORANG The 20s cross themselves out leaving you with an X on the left. X = 500 20 Do the division: When you enter this in a calculator… you will type 500 / 20… and Answer is X=25 mL! Therefore, you will administer 25 mL of the Phenobarbital. Check your answer by cross multiplying (20) x (25) = 500 and (100) x (5) =500 DOSAGE CALCULATION: USING THE FORMULA 𝐃 × 𝐐 =X 𝐇 D = Desired Dose Q = Quantity of Solution/drug H = Strength on Hand X = Unknown quantity of Drug Example 1: Physician orders 500 mg of ibuprofen (desired Dose) for a patient and you have 250 mg (Quantity on Hand) tablets (Quantity of solution) on hand. How many tablets would you administer to the patient? Solution: using the formula, identify the variables and fill it in the formula and then calculate to get your final answer. D ×Q =X H D = 500 mg Q = 1 tablet H = 250 mg X = Unknown quantity of Drug 7 |Y. OBIRIKORANG  Therefore; 500 mg x 1 tablet = 2 tablets 250 mg Answer: 2 tablets will be administered to the patient. Example 2: Physician orders 1500 mg of liquid ibuprofen for a patient. Quantity of Ibuprofen is 500 mg in 1 cc, what volume of ibuprofen will you administer to the patient? Solution: using the formula, identify the variables and fill it in the formula and then calculate to get your final answer. D ×Q =X H D = 1500 mg Q = 1 cc H = 500 mg X = Unknown quantity of Drug Solution: 1500 mg x 1cc = 3 cc Answer: 3 cc will be administered to the patient 500 mg 8 |Y. OBIRIKORANG  PAEDIATRIC DOSAGE AND CONVERSIONS Some have thought that adult medication dosages are universally applied to paediatric patients when in fact this is a misconception. Paediatric patient pharmacokinetics and pharmacodynamics varies among age, body weight, body surface area, and developmental growth and function of various organ systems when compared to adults. The absence of deliberate practice in correct paediatric medication dosing can have potential effects such as; exposing the patient to suboptimal medication dosages, severe systemic toxicity, may even result in fatalities. Paediatric medication dosage calculations are based on the following methods for medication dosing: age-based dosing, body surface area-based dosing, weight-based dosing. Note: Neither method is to be more superior to the other and varies based on a medications chemical properties and age of the patient. However, weight-based dosing is the most commonly used method for calculating recommended medication doses in the paediatric clinical practice. There are several formulas that are used for calculating paediatric dosages namely; Clark's rule Salisbury's rule, Penna's rule, The Body Surface Area rule, Young's rule, Webster's rule, and Fried's rule. However, for the purposes of our discussions, four (4) of the above-mentioned formula are discussed into detail. See figure 1 below. Come along and let’s calculate! 9 |Y. OBIRIKORANG Figure 1: Paediatric dosage calculation chart with formulas 10 |Y. OBIRIKORANG CLARK’S RULE For the Clark’s rule, the weight of paediatric patient may be in pounds (lbs) or kilograms (kg). The formula using pounds (lb) is; Paediatric Dosage = Weight of the child in pounds (lb) x Average Adult Dose 150 lb You can also calculate the paediatric dosage using kilograms for the Clark’s rule. That is; Paediatric Dosage = Weight of the child in kilograms (kg) x Average Adult Dose 68 kg Note: Average Adult dose is the recommended dosage for adult medication use. Come on learner, let us work some examples! Examples; Q1. A paediatrician orders for a child weighing 50 lb to receive IV amoxiclav stat. The average adult dose is 600 mg. What quantity of amoxiclav will be need for this child? Solution Using the Clark’s rule [the pound (lb) version], i.e. Paediatric Dosage = Weight of the child in pounds (lb) x Average Adult Dose 150 lb Identify the variables needed to be put into the formula to solve the question. Weight of the child = 50 lb Average adult dose = 600 mg Now let’s solve: Paediatric Dosage = 50 lb x 600 mg Calculate 150 lb Paediatric dosage = 200 mg This is the quantity of the drug that will be needed for this child. 11 |Y. OBIRIKORANG Q2. A paediatrician orders for a child weighing 38 kg to receive IV amoxiclav stat. The average adult dose is 600 mg. What quantity of amoxiclav will be need for this child? Solution Using the Clark’s rule [the kilogram (kg) version], i.e. Paediatric Dosage = Weight of the child in kilograms (kg) x Average Adult Dose 68 kg Identify the variables needed to be put into the formula to solve the question. Weight of the child = 38 kg Average adult dose = 600 mg Now let’s solve: Paediatric Dosage = 38 kg x 600 mg Calculate 68 kg Paediatric dosage = 335 mg This is the quantity of the drug that will be needed for this child. FRIED’S RULE The rule is used to calculate doses for infants (< one year). The formula is; Infant’s dose (< 1 year) = infant’s age (in months) x Average Adult Dose 150 months Come on learner, let us work an example! Example; Q1. A 4-month-old girl has been admitted to the paediatric ward with a diagnosis bilateral otitis media. The prescriber wants you to calculate a dose of amoxiclav using the Fried’s rule. If the average adult dose is 600 mg, what quantity of drug will be needed for this infant? 12 |Y. OBIRIKORANG Solution Using the Fried’s rule i.e. Infant’s dose (< 1 year) = infant’s age (in months) x Average Adult Dose 150 months Identify the variables needed to be put into the formula to solve the question. Age of the infant = 4 months Average adult dose = 600 mg Now let’s solve: Infant’s Dose = 4 months x 600 mg Calculate 150 months Infant’s Dose = 16 mg This is the quantity of the drug that will be needed for this infant. YOUNG’S RULE The Young’s rule is used to calculate doses for children between the ages of one (1) – twelve (12) years. The formula is; Child’s dose (1-12 years) = child’s age (years) x Average Adult Dose child’s age (years) +12 Come on learner, let us work an example! Example; Q1. A 6-old boy has been admitted to the paediatric ward with a diagnosis of suppurative otitis media. The prescriber wants you to calculate a dose of amoxiclav using the Young’s rule. If the average adult dose is 600 mg, what quantity of drug will be needed for this child? Solution Using the Young’s rule i.e. Child’s dose (1-12 years) = child’s age (years) x Average Adult Dose child’s age (years) +12 13 |Y. OBIRIKORANG Identify the variables needed to be put into the formula to solve the question. Age of the child = 6 years Average adult dose = 600 mg Now let’s solve: Child’s Dose = 6 years x 600 mg Calculate 6 years +12 Infant’s Dose = 200 mg This is the quantity of the drug that will be needed for this child. THE BODY SURFACE AREA (BSA) The method can also be used to calculate the paediatric doses. The formula is; Child’s dose = surface area of the child (square metres – m2) x Average Adult Dose 1.73 m2 The child’s body surface area can be determined from a nomogram (figure 1) which is a more precise way to calculate the body surface area in paediatrics or calculated using a formula. When using the formula in solving these BSA problems you will need a calculator that configures square roots of numbers, round your answers as discussed earlier, and memorize the formulas below. Therefore, before solving body surface area you need to commit to memory the following formulas below. Figure 2: Paediatric dosage calculation based on body surface area 14 |Y. OBIRIKORANG NOTE: The first two formulas will help you to calculate the body surface area and you will select which formula to use based on if the scenario gave you the patient’s weight and height in the household or metric system. You will use the FIRST formula below if the weight and height are in kilograms (kg) and centimetres (cm). You will use the SECOND formula below if the weight and height are in pounds (lbs) and inches (in). The last formula will help you calculate a child’s dose based on the child’s BSA and the average/normal adult dose. Come on learner, let us work some examples! Examples; Q1. Your patient weighs 163 lb and is 5 feet 7 inches. What is the patient’s BSA? Solution First, identify the variables needed to be put into the formula to solve the question. Weight = 163 lb Height = 5 feet 7 inches Based on this information, you will be using the second formula in figure 2. Now let’s solve: 15 |Y. OBIRIKORANG Q2. Your patient weighs 27.2 kg and is 91 cm. What is the patient’s BSA? Solution First, identify the variables needed to be put into the formula to solve the question. Weight = 27.2 kg Height = 91 cm Based on this information, you will be using the first formula in figure 2 above. Now let’s solve: 16 |Y. OBIRIKORANG Q3. A paediatric patient is ordered a medication dose of 10 mg/ m2/day by mouth for 7 days. The patient weighs 46 lb and is 3 feet 9 inches. What is the daily dose of medication the patient will receive? Solution First, identify the variables needed to be put into the formula to solve the question Weight = 46 lb Height = 3 feet 9 inches Based on this information, you will be using the second formula in figure 2 above. Physician’s order = 10 mg/ m2/day So, we are going to solve for the daily dose. Now let’s solve! 17 |Y. OBIRIKORANG NOTE: Paediatric dosing is based on weight and it is usually expressed in a range. There are several steps to determining if an ordered medication and dose are within the safe range for the patient’s weight. So far as the dose is outside the range, either below the range or above the range the dose is not safe for the patient. Now let’s solve! Example 1: Physician Order: Cefuroxime 2 grams every 8 hours. Safe dose for this drug: 75-150 mg/kg/day. Patient weight: 30 kg 18 |Y. OBIRIKORANG Solution 1. Determine what the safe dose is with this patient’s weight. Multiply the weight in kg by the low safe dose and the high safe dose. This will give you the range. (30 kg) x (75 mg/kg/day) = 2250 mg per day (30 kg) x (150 mg/kg/day) = 4500 mg per day The safe range for this patient’s weight is 2250-4500 mg (2.250 g-4.5 g) per day 2. You just calculated a range PER DAY. Is this how the drug is ordered? If not, then calculate how much you would give PER DOSE. In step #1 we determined the dose PER DAY. In the ordered example the drug is given every 8 h. We need to take the dose determined in step 1 and divide it by 3 because there are 3 eight-hour periods in a day. So… Divide the safe range 2250-4500 mg by 3 The safe range for this patient is 750-1500 mg (0.75 g-1.5 g) per dose 3. Compare our calculated safe range with the ordered dose. Does the ordered dose fall within our calculated range? If so, it is a safe dose. If not, it is not a safe dose! This order is not within the safe range because the order is greater than the safe range. Example 2: MD orders 300 mg of Ibuprophen to be taken by 6 kg infant every 4 hours. Label shows 75 – 150 mg/kg per day. Is the physician’s order within normal range? Solution: 6 x 75 = 450 mg (minimum dosage per day); 150 X6 = 900 mg (maximum dosage per day) 19 |Y. OBIRIKORANG  24 ÷ 4 = 6 dosages: 300 x 6 = 1800 mg Answer: Dosage is not within range IV Dosage Calculations [Amount of fluid to be infused (mL)] X [Drop Factor (gtt/mL)] = drop (gtt) rate per minute Time (in minutes) to infuse Example 1: Dr A. orders your patient to receive 125 mL of D5W an hour for the next 8 hours. The nursing unit uses tubing with a drop factor of 10 gtt/mL. What is the drop rate per minute? Solution: Convert 1 hour to 60 minutes: 125 mL x 10 gtt = 20.83 or 21 gtt/min 60 minutes 1 mL Answer: 21 gtt/min Example 2: Dr B. orders a litre of D5W to run this 8-hour shift. The drop factor is 15 gtt/mL. What is the drop rate per minute? Solution: Convert 1 litre = 1000 mL of solution, next; Convert 8 hours to minutes (8 X 60 minutes) = 480 minutes 1000 mL x 15 gtt = 31.25 or 31 gtt/min 480 min 1 mL Answer: 31 gtt/min 20 |Y. OBIRIKORANG Example 3: Your patient weighs 200 lb and the order is to infuse 250 mg dobutamine in 500 mL NS at 10 mcg/kg/min. How many milligrams of dobutamine will infuse per hour? Solution: Conversions: 200 ÷ 2.2= 90.90 kg 60 minutes = 1 hour 10 mcg x 90.90 kg x 60 min=54540 mcg/hour Convert mcg to mg; 54540 mcg/hour = 54.54 mg/h or 54.5 mg/h 1000 Answer: 54.5 mg/h ** A different type of drip calculation that you may see: Example 4: If you have a drip rate of 20 gtt/min and your IV set delivers 15 gtt/mL. How many mL will the patient receive in 2 hours? Solution 1. Determine how many minutes are in 2 hours. 60 min x 2 = 120 minutes in 2 hours. 2. In 2 hours, if something drips at 20 gtt/min, how many drops will occur in 120 minutes? Multiply the number of minutes by the drip rate. 120 minutes x 20 gtt/min = 2400 gtt (total drops in 2 hours). 3. Now take into account the tubing (“your set delivers 15 gtt/mL”) which converts the drips to mL. Divide the total drops by the set delivery. 2400 gtt will give you the total mL given in 2 hours. This is what you are looking for! 15 (gtt/mL) Answer: 160 mL in 2 hours 21 |Y. OBIRIKORANG INSTRUCTIONS TO ENSURE A CORRECT ANSWER Round all answers to medication problems to the nearest tenth. Kilogram weights should be rounded immediately, before proceeding with the problem. Otherwise, don't round until you get to the final answer. Answers that are not correctly rounded to the nearest tenth are graded as incorrect. For example, 3.25 is rounded to 3.3. I.V. flow problems are rounded to the nearest whole drop. For example, 33.3 is rounded to 33 drops. If the answer is less than 1, with no whole number before the decimal point, ALWAYS place a zero in front of the decimal. This is a safety issue. An answer on the test not preceded by a zero as appropriate will be graded as an incorrect notation. For example,.7 must be written as 0.7 in order to be considered appropriate notation. If the answer is 1,000 or above indicate the number with a comma. ALWAYS omit terminal zeros. Answer containing terminal zeros violate patient safety standards, and will be graded as an incorrect notation. For example, 12.50 must be written as 12.5 in order to be considered appropriate notation. The answer must be labelled in correct units. In incorrectly labelled answer is considered a wrong answer. For example, 7 mg is not the same as 7 mL. In an exam, select ONE final answer. If any selected answer in the options is incorrect, the answer is graded an incorrect. If no answer is selected, then the question is determined to be unanswered and graded as incorrect. 22 |Y. OBIRIKORANG EXERCISES; TRY YOUR HANDS ON THE FOLLOWING EXERCISES 1. A child is to receive a total of 240 mg per day of a medication. The medication is given every 8 hours and is available in a solution of 80 mg per 10 mL. How many tablespoons will the child receive with each dose? 2. A child is to receive an ordered antibiotic of 500 units/kg/day. Child’s weight is 66 lb or 30 kg. The medication comes in a powder in 5000-unit vials. The nurse reconstitutes by adding diluent to yield 2 mL of solution. What volume of the antibiotic should the child receive per day? 3. A medication comes in 25 mg tablets and is ordered 2 times a day for a total of 200 mg per day. How many tablets should a patient receive with each dose? 4. A medication order is 600 mg PO every 3 hours. What quantity of the medication in grams will be given per day? 5. A paediatric patient is 65 lb and 4 feet 5 inches. The physician orders an oral medication that has a normal adult dose of 250 mg. What quantity of this medication will be administered? 6. A paediatric patient has a body surface area of 0.88 m2. The physician orders an IV medication that has a normal adult dose of 125 mg. You’re supplied with a vial that reads 30 mg/mL. What volume of the medication will you administer to this patient? 7. Using the Clark’s rule, what is the dose for a 12-year-old girl who weighs 31.7 kg if the average adult dose is 500 mg? 8. The paediatric dose for a 9-year-old child to be determined. You learn that the adult dose for the same drug is 200 mg. Using Young’s rule, what dose should the child be given? 9. A patient has an aminophylline IV drip ordered for acute asthma, to run at 20 mL/hour. No IV infusion controller is available right now. What drop rate will be set if micro-drip tubing (60 gtt/mL) is used? 10. A patient is receiving an infusion of 200 units of heparin per hour. The concentration of heparin is 20,000 units per 500 mL. What rate per hour will the medication be set to infuse at? 23 |Y. OBIRIKORANG 11. A patient is to receive 2000 mg of a medication in 4 divided doses. The capsules are 500 mg each. How many capsules will be given with each dose? 12. A patient is to receive 750 mL of Lactated Ringers over 4 hours. The drop factor is 20 gtt/mL. At what drop rate will the you infuse this amount of ringer’s lactate? 13. A patient is to receive heparin at a bolus dose of 200 units per kg. The patient weighs 200 lb or 91 kg. The concentration of heparin is 1000 units per mL. What volume of heparin will the patient receive? 14. A patient who weighs 150 lb is to receive 50 mg/kg of a medication every 8 hours. What quantity of the medication will the patient receive each day? 15. An IV tubing lists its delivery rate as 20 gtt/mL. The drip rate for a medication is set at 60 gtt/min. What volume of fluid will the patient receive in 6 hours? 16. An IV with Nitroglycerin is infusing at 8 mL/hr. The concentration of the IV is 50 mg in 250 mL of D5W. What quantity of nitroglycerin is the patient receiving? 17. If you have a drip rate of 20 gtt/min and your IV set delivers 15 gtt/mL. What volume of fluid will the patient receive in 2 hours? 18. Ordered: Lactated Ringers 1000 mL over eight hours. The drip factor is 15 gtt/mL. At what drop rate should this drug infuse? 19. Ordered: Zovirax 500 mg IV in 90 mL of D5W over 60 minutes. The Drip Factor is 15 gtt/mL. What drop rate should this drug infuse? 20. The order is for 60 mg of drug X. The label reads 25 mg/ 2 mL. What volume of drug X will be given? 21. You have an order to give a patient a 1 litre NS bolus over 2 hours, then 100 mL/hr for 12 hours. How much fluid will the patient receive in 6 hours? 22. Your order reads ceftizoxime 1 g IV every 8 hours. The pharmacy supplies it in 100 mL D5W. You need to infuse it over 30 minutes. With a drop factor of 10, what drip rate will you set? 23. If an oral medication comes supplied at a concentration of 50 mg per ml, what volume of the medication would deliver a dose of 300 mg? 24 |Y. OBIRIKORANG 24. A 500 mg quantity of drug A is administered at time zero. The half-life of the drug is 5 hours. What quantity of the drug is expected to remain in plasma after four (4) half- lives? 25. The prescription is 3 mg/kg Solu-Medrol for a child weighing 18 kg. Solu-Medrol is available as 125 mg / 2 ml. What volume must the nurse administer? 26. The prescription is for 12.5 mg of drug X. The label reads 75 mg/ml. What volume would you administer? 27. The prescription is for 4000 ml of Normal Saline to run over a 24-hour period. The drop factor of the I.V tubing is 15 gtt/ml. At what drop rate will you infuse this volume of Normal Saline? 28. The prescription is for 500 μg of thyroxin. The label reads 0.2 mg tablet. How many tablet(s) would you give? 29. A patient is to receive 3 L of Normal Saline in 18 hours. What volume of Normal Saline would the patient have received after 10 hours? 30. A patient is to be given 130 mg of Gentamycin by IV injection. The drug is available at a concentration of 80 mg/2 ml. What volume of Gentamycin should the nurse administer? 31. The prescription reads: “Infuse 1500 ml of 5 % dextrose over 12 hours.” With a tubing set of drop factor 10 gtt/ml, what would be the drop rate? 32. The prescription is for 80 mg Phenytoin to be given orally every 8 hours for 3 days. Phenytoin is available as 125 mg/ 5 ml. What volume would the nurse administer with each dose? 33. The physician has ordered Fentanyl drip for sedation for a patient on the ventilator. The drip comes as 1 mg/100 ml Normal Saline. The dosing rate is 200 μg/h. Calculate the rate of infusion in ml/h? 34. You have a patient who have been diagnosed with an onset of atrial fibrillation. The doctor has ordered a Heparin drip to be infused at 1000 units/h. The drip comes as Heparin 25000 units/500 ml NS. You also have to give an IV push dose of 500 units that comes in a vial Heparin 1000 units/2 ml. What volume of fluid will the patient receive in the first hour? 35. You have an order to give a patient 1.5 L bolus over 2 hours, then 150 ml/h for 24 hours. What is the total volume of fluid the patient will receive? (leave your answer in litres, L) 25 |Y. OBIRIKORANG 36. You have a patient on Dopamine drip ordered at 15 μg/kg/min. The drip comes as 320 mg /100 ml D5W. The patient weighs 85 kg. What volume of Dopamine will the patient receive per hour? 37. A doctor has ordered 1.5 L Normal Saline bolus to infuse over 2 hours. What rate will you set the pump to infuse this volume of Normal Saline? 38. A patient that is NPO has a fever and needs Tylenol. The MD has prescribed IV Tylenol 850 mg q6h PRN for temperature of 39.3 oC or above. The bottle is supplied at a concentration of 1000 mg/100 ml. The prescription is to infuse a dose in 15 minutes. a) What volume of Tylenol will be infused? b) What rate will a dose be set to infuse? 39. Your patient is being treated for atrial fibrillation and the order is to infuse 1.5 mg Digoxin at 8 μg/kg as a loading dose. If Digoxin comes supplied as 0.25 mg/ ml and your patient weighs 120 lb. a) What quantity of digoxin will you prepare for your patient? b) Is the dose safe for your patient and why? c) What volume of digoxin will you administer to your patient? 40. The physician orders Ativan 1 mg IV push for an agitated patient. The vial comes at a concentration of 2 mg/ml. What volume will the nurse deliver? 41. A safe maintenance dose of Aminophylline is 0.36 mg/kg/hour. It is supplied as 100 mg/100 ml. Your patient weighs 150 pounds and is receiving 20 ml/h. Is the dose safe? 42. Your order reads Labetalol 40 mg IV push every 10 minutes until blood pressure is lower than140/90 mmHg. You have labetalol 5 mg/ml available. What volume of Labetalol would you administer? 43. Give Ceftazidime 50 mg/kg PO 8 hourly to a child who weighs 25.5 kg. Ceftazidime is available in an oral suspension labelled 100 mg/mL. What volume of Ceftazidime would the nurse administer per dose? 44. Miss Beans needs Paracetamol, 20 mg/kg/day (in four divided doses). She is 46 years old and weighs 80 kg. Work out the single dose to be given. 45. A 10-year-old boy needs to be prescribed an antibacterial drug. He weighs 32 kg and stands at 1.4 meters tall. The adult dose for the same medicine is 75 mg. The boy ends up being prescribed 35 mg. 26 |Y. OBIRIKORANG  a) Which formula – Clark’s rule or Young’s rule – was used to arrive at this specific dose? b) Use the body surface area rule to also calculate the dose for this boy. 46. A 6-year-old child weighing 19.5 kg is to receive Fluconazole for systemic candida infection. The safe dose range is 6 – 12 mg/kg/day not to exceed 600 mg/day. The Fluconazole is to be given IV bolus for day 1 and orally qday for 3 days. It is available in the following dosage form strength: injection solution 2 mg/ mL and oral suspension 40 mg/mL. a) What is the safe dose range for this patient? b) Based on your calculations in a) above, is it safe for the child if the prescriber orders for 120 mg to be administered as the IV bolus? Why? c) What volume of the medication will be administered on day one based on the doctor’s ordered dose in b) above? d) What volume of the medication will be administered on day 2 for the doctor’s order? 47. A patient is given 1.5 litres of Dextrose 5% over 4 hours. If the drop factor for the IV tubing is 15 gtt/mL, what will be the drip rate? 48. A six-month old child is to receive a dose of amoxicillin. The usual adult dose is 500 mg. calculate the quantity of amoxicillin this infant will be given. 49. Clarithromycin has been ordered for a child whose BSA is 0.75 m2. The usual adult dose is 500 mg. It is available in an oral suspension as 250 mg/ 5 mL. What volume would you administer per dose? 50. Convert the following: (0.5 mark each) a) 200 mg to μg b) 850 g to kg 51. How many tablespoons are there in 60 mL? 52. A patient is prescribed 1.5 L of 0.9 % saline to run over 12 hours with a drip rate of 20 gtt/min. At what drop factor will you set the giving set? 53. How long will you infuse 1000 mL of 5 % dextrose in saline with a drop factor of 20 gtt/mL and drip rate of 15 gtt/min? (Leave your answer in hours) 54. A child weighing 16.5 kg and is prescribed a medication for 0.8 mg/kg/dose. The stock strength is 20 mg/2 mL. The child is to be given this medication for 12 hourly for 48 hours. 27 |Y. OBIRIKORANG  a) What quantity of the medication will you give? b) What volume will you give the patient? c) Calculate the total volume of the medication the child received by the end of the 48 hours. 55. Attah weighs 98 kg. It has been decided to give him 6 mg/kg/dose of Ibuprofen. Work out the dose to be given. 56. Mr Gobble is to receive 2.5 litres of normal saline to be infused in 24 hours. The giving set delivers 15 gtt/ml. How much fluid would she have received by the 12th hour? 57. Diclofenac is available in 50 mg and 100 mg strengths. A patient is prescribed a total dose of 375 mg, how many tablets will you give them? 58. An IV drip is set to a flow rate of 55 mL/h. The doctor changes the flow rate to 47,500 µL/h. a) How much less is the patient now getting per hour? b) How much will the patient now get in the next 12 hours? (Leave your answer in mL) 59. The order is: Ceftazidime 50 mg/kg PO t.i.d. for 5 days to a child who weighs 16 kg. Ceftazidime is available in an oral suspension labelled 100 mg/mL. What volume of Ceftazidime would you administer for the first 24 hours? 60. A 6 kg child is ordered a medication for 5 mg/kg/day in 4 divided doses per day. What quantity would you administer per dose? 28 |Y. OBIRIKORANG