Pharmaceutical Dosage Form I Lecture Notes PDF

Pharmaceutical Dosage form I By Lecture 2 Dosage form I This course aims to cover the principles of the pharmaceutical calculations and formulation of different dosage forms as solutions, emulsions, suspensions and colloids. Also, different types of incompatibilities (physical...

Pharmaceutical Dosage form I By Lecture 2 Dosage form I This course aims to cover the principles of the pharmaceutical calculations and formulation of different dosage forms as solutions, emulsions, suspensions and colloids. Also, different types of incompatibilities (physical, chemical and therapeutic) will be presented. 1- Systems of Pharmaceutical Measurement 2- Roman Numerals  Roman Numerals ❖ Roman Numerals represents quantities in prescriptions when its ingredients are measured by apothecaries’s system. ❖ These 8 letters of fixed values are used in Roman system: SS IVXLCDM ss I V X L C D M 0.5 1 5 10 50 100 500 1000  ss 0.5 XI 11 I 1 XII 12 II 2 XV 15 III 3 XVI 16 IV 4 XIX 19 V 5 XXI 21 VI 6 L 50 VII 7 LX 60 VIII 8 D 500 IX 9 CD 400 X 10 DC 600  Rules of expressing the quantities:  Other quantities are expressed by combining these letters by the general rule that; 1- The first rule:  When the second of two letters has a value equal to or smaller than that of the first,  their values are to be added (i.e., summation).  Examples II=2 Lv= 55 Ci= 101 MI= 1001 Dv =505 III= 3 Li=51 CV=105 MV=1005 Dx=510 VI= 6 Lx=60 CX=110 MX =1010 DL=550 MDCLXVI= VII=7 Lxvi=66 CL=150 ML=1050 1666 2- The second rule:  When the second has a value greater than that of the first, the smaller should be subtracted from the larger. Examples iv= 4 xxiv =24 xLiv = 44 xcix = 99 cdxLiv =444 ix= 9 xxxix =39 cd = 400 cdxc =490 xiv =14 xL =40 xc =90 cdi = 401 cm =900 xix =19 xLi = 41 cdxL = 440 cmxcix = 999 Note…………….  Important notes  You cannot repeat a Roman numeral over three times. If you want to write the Arabic number “40” as a Roman numeral, you can do it like this: XXXX. Instead, you would document XL (Subtractive Rule).  The letters V, L, and D; each alone is not to be added to itself, (eg; VV, LL, DD are incorrect values, and these letters are never to be subtracted.  The letter V is to be added to; X as (XV = 15), L as (LV = 55), C as (CV = 105), D as (DV = 505) and M as (MV = 1005).  The letter L is to be added to; C as (CL = 150), D as (DL = 550) and M as (ML = 1050).  The letter D is to be added to; M as (MD = 1500).  The letters I, C and X are added to themselves and to any greater numbers two-fold and three-fold.  Usually; I, C and X are used as subtraction.  Each is used to subtract only from the two following greater numbers  thus X is used to substract only from L and C, but not from D.  A subtractor is placed so as to precede only one character higher than itself.  Ex: 19 = XIX but not IXX. Examples II = 2 XX = 20 CC = 200 III = 3 XXX = 30 CCC = 300 VI = 6 LX = 60 DC = 600 VII = 7 LXX = 70 DCC = 700 VIII = 8 LXXX = 80 DCCC = 800 XII = 12 DXXX = 530 CXXX = 130  Solved Examples on Roman Numerals Example 1: ► Write 69 in roman numerals. Solution: 69 = 60 + 9 = (50 + 10) + (10 - 1) = LX + IX = LXIX Thus, 69 = LXIX. Example 2: ► Convert 1984 into the roman numeral. Solution: Break the number 1984 into 1000, 900, 80 and 4, then perform each conversion As, 1000 + 900 + 80 + 4 = 1984 1000 = M 900 = CM 80 = LXXX 4 = IV 1000 + 900 + 80 + 4 = 1984, So, 1984 = MCMLXXXIV Example 3: ► Convert 1774 to Roman Numerals. Solution: Break 1774 into 1000, 700, 70, 4 and then do each conversion 1000 = M 700 = DCC 70 = LXX 4 = IV 1000+700+70+4 = 1774, Hence, 1774 = MDCCLXXIV Example 4: ► Compute the following roman numeral MXXII - LXX - LII. Solution: Given: MXXII - LXX - LII. We know that MXXII = 1022, LXX = 70 and LII = 52. Now, substituting these numbers in the Roman numeral letters, we get; MXXII - LXX - LII = 1022 - 70 - 52. MXXII - LXX - LII = 900. Hence, the number 900 in the Roman numeral is CM.  Pharmaceutical calculations 1- Percentage The term percent and its corresponding sign (%) mean "by the hundred" or "in a hundred," or may also be expressed as a ratio.  For example, 50% means 50 parts in 100 of the same kind, and may be expressed as 50/100 or 0.50 Percents are usually changed to equivalent decimal fractions by dividing the expressed number by 100.  Ex: 12.5% =12.5/100 or 0.125 - 0.05 % = 0.05/100, or 0.0005. Percent weight-in-volume (w/v) expresses the number of grams of a constituent in 100 mL of solution or liquid preparation.  It is expressed as: % w/v. Percent volume-in-volume (v/v) expresses the number of milliliters of a constituent in 100 mL of solution or liquid preparation.  It expressed as:% v/v. Percent weight-in-weight (w/w) expresses the number of grams of a constituent in 100 g of solution or preparation. It expressed as: % w/w. The term percent, or symbol, %, when used without qualification means:  for solutions or suspensions of solids in liquids, % w/v  for solutions of liquids in liquids, % v/v.  for mixtures of solids or semisolids, % w/w.  for solutions of gases in liquids, % w/v  2- Ratio strength The concentration of weak solutions or liquid preparations is frequently expressed in terms of ratio strength. For example: 5% means 5 parts per 100 or 5:100; thus, 5:100 = 1: 20.  1/1000, used to designate a concentration, is to be interpreted as follows: - For solids in liquids = 1 g of solute or constituent in 1000 mL of solution or liquid preparation. - For liquids in liquids = 1 mL of constituent in 1000 mL of solution or liquid preparation. - For solids in solids = 1 g of constituent in 1000 g of mixture.  Express 0.02% as a ratio strength. Express 1: 4000 as a percentage strength. 1 /4000 = X / 100 X = 0.025 % Percentage strength = 0.025 % Converting a Ratio to a Percent:  Solve 3:500 = …………… = 0.6% Converting a Ratio to a Percent:  3- Parts per million (PPM)  The strengths of very dilute solutions are commonly expressed in terms of parts per million (ppm) i.e., the number of parts of the agent per 1 million parts of the whole.  It may be used to describe the quantities of trace impurities in chemical samples and trace elements in biologic samples. Example: Express 5 ppm of iron in water in percent strength and ratio strength. 5 ppm = 5 parts in 1,000,000 parts 5/1000000 X 100 = 0.0005 % Routes of drug administration  A drug will produce its action only when it enters the body, tissue or cells (i.e. site of action).  The entrance, through which a drug is delivered, is called the route of drug administration. A) Enteral routes B) Parenteral administration C) Others A) Enteral routes (administering the drug by mouth): 1) Oral route: most commonly used for drug administration. Advantage: 1. Most convenient to the patient. 2. Acceptable. 3. Painless. 4. Safe Disadvantage: 1-Drug action is slow, thus not suitable for emergency. 2- Irritant drugs cannot be administrated. 3- May not be useful in the presence of vomiting. 4- Cannot be used for unconscious patient. 5- Digestive juices destroy some drugs (Penicillin G). 6- The drug must pass to the liver on its way to the general circulation (first pass metabolism) e.g. Propranolol. 2) Sublingual & buccal  The highly lipid soluble and non-irritating drugs (e.g.: nitroglycerine) in the form of tablets or pellets is placed under the tongue (sublingual).  Or (buccal route) placement of drug between the cheek and gum. Advantage: 1-Rapid onset of action. 2- Easy to be used. 3- The effect can be terminated by spitting out the tablet. 4- Avoiding degradation of certain drugs by gastric acid & first pass metabolism in the liver. Disadvantage: 1- Irritation of mucus membrane. B-parenteral administration  Administration by injection includes the following routes:  Subcutaneous (under the skin)  Intramuscular (in a muscle)  Intravenous (in a vein)  Intraarterial (into an artery), e.g. vasodilator drugs in the treatment of vasospasm.  Intracardiac (into the heart), e.g. adrenaline during cardiopulmonary resuscitation.  Intradermal, (into the skin itself) is used for skin testing some allergens.  Intrathecal (into the spinal canal) is most commonly used for spinal anesthesia and chemotherapy.  Intraperitoneal, (infusion or injection into the peritoneum) e.g. peritoneal dialysis. Through the Skin C) Others 1-Inhalation route  Provide rapid delivery of drug across the large surface area of respiratory tract. Advantage: 1-Rapid effect. 2- Convenient for patient with respiratory disorders. Disadvantage: 1- The drug must not be irritant. 2- Obstructed bronchi cause the therapy to fail. 2-Rectal route  A suppository is prescribed for people who cannot take a drug orally because they have nausea, or have restrictions on eating, as is required before and after many surgical operations. Advantages 1- By-pass liver, reduced first-pass effect. 2- Useful for patients unable to take drugs orally. 3-If patient is nauseous or vomiting. Disadvantages 1-Not well accepted. 3-May cause rectal inflammation. 3-Ocular route  Liquid eye drops are relatively easy to use but may run off the eye too quickly to be absorbed well.  Gel and ointment formulations keep the drug in contact with the eye surface longer, but they may blurred vision. 4-Otic route  Drugs used to treat ear inflammation and infection can be applied directly to the affected ears. 5-Nasal route  If a drug is to be breathed in and absorbed through the thin mucous membrane that lines the nasal passages.  Once absorbed, the drug enters the bloodstream.  Drugs administered by this route generally work quickly. 6-Topical route:  When local effect of drug is desired (as ointments, creams, lotions) may be used for skin, eye, intranasal minimize systemic absorption, easy for patient, e.g. hydrocortisone cream. 7-Transdermal route  As in cases of unstable angina.  Achieves systemic effect.  Rate of absorption varies markedly depending on the physical characteristics of skin at site of application as well as lipid solubility of drug. Q1: Scientific term 1- Route of administration in which drug is placed between the cheek and gum. 2- Two routes of administration in which the degradation of drugs by first pass metabolism can be avoided. 3- The strengths of very dilute solutions are commonly expressed in …………….. Q2: Converting a Ratio to a Percent 1:100 =……………. = 1% 1:200 = …………… = 0.5% 3:500 = …………… = 0.6% 1:2500 = ………….. = 0.04% 1:10,000 = ………… = 0.01% Q3 : (T or F) 1. The concentration of weak solutions or liquid preparations is frequently expressed in terms of ppm. 2. Transdermal route can achieves systemic effect.  Q4: Complete the table XVIII = ……………. XIV = ……………. LX I I I = ……………. CXVIII = ……………. LX IV = ……………. MCMXVI = 1000+(1000-100)+10+5+1 = 1916