Pharmaceutical Calculations

Pharmaceutical Calculations 1. How much Lidocaine is required to prepare 1 : 1000, 30 cc of solution of Lidocaine? a. 10 mg b. 0.03 mg c. 30 mg d. 300 mg 2. How many cc of 75 % alcohol should mix with 10 % of 1000cc alcohol to prepare 30% of 500cc alcohol solution? a. 346.16 cc b. 234.43 cc c. 153.84 cc d. 121.12 cc 3. If 60 gm of 1% hydrocortisone is mixed with 80 gm of 2.5% of hydrocortisone, what is the % of hydrocortisone in final mixture? a. 2.2 % w/w b. 1.85 % w/w c. 0.25 % w/w d. 1.75 % w/w 4. If 1000 tablets of Risperdal 1 mg cost $ 2250 and % mark up on prescription is 20, what would be the retail price of 30 tablets? a. $ 150 b. $ 17 c. $ 500 d. $ 81 5. If the ratio of ionized to unionized species of drug is 103 and PKa = 2.2, what is the PH of the solution? a. 2.2 b. 0.8 c. 5.2 d. 3.0 6. If dropper is calibrated to deliver 325 mg of iron sulfate in 0.6 cc and adult dose of drug is 325 mg , what is the dose of a drug in cc for a 15 months-old infant?

a. 1.2 cc b. 0.3 cc c. 0.06 cc d. 0.01 cc 7. If the dose of a drug is 10 mg/kg/day, how many 250 mg/100cc ready infusion-bags require to fill above order? Patient's weight is 156 lbs. a. 1 bag b. 2 bags c. 3 bags d. 5 bags 8. How much of atropine is required to prepare 240cc in such way that when 1 teaspoonful of the solution is diluted to 1 pint gives 1 in 500 solution? a. 2.25 gm b. 46.08 gm c. 35.15 gm d. 25.35 gm 9. How much sodium bicarbonate powder is required to prepare 240cc of 0.10 N solution of sodium bicarbonate? a. 1.35 gm b. 3.25 gm c. 4.81 gm d. 2.016 gm 10. How many meq of Na+ are present in 0.9% 250cc normal saline solution? [Na+ = 23, Cl- = 35.5] a. 23.12 meq b. 15.17 meq c. 53.15 meq d. 38.46 meq 11. If the probability of success in Null hypothesis is 0.6, what is the probability of failure? a. 0.3 b. 0.9 c. 0.6 d. 0.4

12. How many grams of cocabutter are required to dispense 12 suppositories of tannic acid each weighing 2 gm and contain 400 mg of tannic acid? a. 21.23 gm b. 18.67 gm c. 14.12 gm d. 13.25 gm 13. What is the "mode" or "median" of the following values? 120, 135, 140, 118, 175, 105, 115, 190 a. 135 b. 118 c. 127.5 d. 175 14. If the concentration of reactant M is half in a reaction that is third order in M, by what factor will rate of reaction change? a. 1/8 times b. 1/4 times c. 8 times d. 4 times 15. What is the rate of constant after 90 minutes if the initial concentration of drug is 500mg/cc and 50mg/cc after 90 minutes? (First Order Kinetic) a. 0.051 min-1 b. 0.025 min-1 c. 0.35 min-1 d. 0.86 min-1 16. If the total body clearance of the patient is 2100cc/hr and hepatic clearance is 300cc /hr, what is the status of renal function in a patient? a. Excellent b. Normal c. Moderately impaired d. Severely impaired 17. How many grams of sodium chloride are required to prepare 250cc of 1% boric acid solution to isotonic with eye tears?

FP of 1% boric acid = -0.29o C FP of 1% sodium chloride = - 0.58oC FP of blood = -0.52o C a. 250 mg b. 325 mg c. 991 mg d. 1221 mg Answers 1. (c) 1: 1000 generally interprets as 1 gm in 1000cc solution. The amount of lidocaine in 30cc of 1:1000 solution can be calculated as follows: = 30 x 1/1000 = 0.03 gm = 30 milligrams. 2. (c) To solve this type of problem, we need to use alligation method. 75 20 (75%) 30 10 45 (10%) Total parts 65 (30%) To prepare 65 (30%) 20 parts (75%) need To prepare 500 (30%) ? = 500 x 20/65 = 153.84cc (75%) alcohol If we mixed 153.84 cc of 75% alcohol with 346.16cc [500cc - 153.84] of 10% alcohol, then we can get 500cc of 30% alcohol solution. 3.(b) Amount of Hydrocortisone in 60 gm, 1% = 60/100 = 0.6 gm of hydrocortisone. Amount of hydrocortisone in 80 gm, 2.5% = 80 x 2.5/100 = 2 gm hydrocortisone % amount of hydrocortisone in final mixture = 100 x 2.6 (2gm + 0.6gm)/140 (80gm + 60gm) = 1.85% w/w. 4. (d) 1000 tablets of Risperdal 1mg cost $ 2250. The % mark up on prescription is 20%. Therefore retail price of 1000 tablets would be = 120 x 2250/100 = $ 2700 ** For each $ 100 cost = $120 retail cost** Price for 30 tablet would be = 30 x 2700/1000 = $ 81 5. (c) A pH of the solution can be found by the following formula: pH = pKa + log ionize/unionize = 2.2 + log 103 = 2.2 + 3

= 5.2 6. (c) 0.06cc. According to Fried’s rule = age in months/150 x adult dose = 15 x 325/150 = 32.5 mg The dropper is calibrated to deliver 325 mg of Iron sulfate in 0.6 cc, therefore = 0.6 x 32.5/325 = 0.06cc 7. (c) Patient weight is 156 lbs, therefore weight in Kg would be 156/2.2 = 70.9 kg A normal therapeutically recommended dose of drug is 10mg/kg/day, therefore dose in above patient = 10 x 70.9 = 709 mg Each ready-infusion-bag contains 250 mg of drug, so number of bags require to fill order would be = 709/250 = 2.83 @ 3 bags. 8. (b) To solve this kind of problem, we must first find out the amount of drug present in final solution. Amount of atropine in 1 pint, 1 in 500 soln . = 480 x 1 /500= 0.96 gm of atropine. Now, 0.96 gm of drug must be present in 1 teaspoonful of drug solution, therefore we can say 5cc (1 teaspoonful) contains 0.96 gm 240cc solution requires ? = 240 x 0.96/5 = 46.08 gm of atropine. 9. (d) Gram equivalent weights of solute in 1 liter of solution is defined as normality, therefore 1N solution of sodium bicarbonate will contain 84 gms in 1000 cc. We want to find quantity of sodium bicarbonate in 240cc, 0.1 N solution, 1 N solution contains 84 gm 0.1 N solution contains ? = 0.1 x 84 = 8.4 gms/1000cc. 240cc solution will contain: = 240 x 8.4/1000 = 2.016 gm of NaHCO3 10. (d) An amount of sodium chloride presents in 250 cc of 0.9% NaCl, = 250 x 0.9/100 = 2.25 gm NaCl Total equivalents Na+ = weight in gm equivalent wt = 2.25/58.5 = 0.03846 equivalents 11. (d) The sum of probability of success and failure would be equal to 1 in Null hypothesis and can be expressed by following formula: p + q = 1, where p = probability of success

q = probability of failure q=1-p = 1- 0.6 = 0.4 12. (b) We want to dispense 12 suppositories each weighing 2gm and containing 400mg of tannic acid, Amount of coca butter = 2 gm x 12 = 24 gm Amount of tannic acid = 0.4 gm x 12 = 4.8 gm. Displacement value of tannic acid is 0.9, therefore = 4.8/0.9 = 5.33 gm of base will displace 4.8 gm tannic acid = 5.33 gm cocabutter Amount of coca butter = 24 gm - 5.33 gm = 18.67 gm 13. (c) Median or Mode is generally expressed as a middle value of experiment, if number of values are even, then average of middle values should be considered. To find median or mode of experiment data, one should first arrange the data in ascending or descending order. In our example, 105, 115, 118, 120, 135, 140, 175, 190 = (120 + 135)/2 = 127.50 14. (a) The concentration of reactant M is half in a reaction that is third order in kinetic, dx/dt = k (a-x) (b-x) (c-x) = k (a-x)3 where a=b=c = k (M)3 now M = M/2 = k (M/2)3 = 1 /8 k (M)3 15. (b) 0.025 min-1 For the first order kinetic, K = 2.303/t x log Co/C = 2.303/90 x log 500/50 = 2.303/90 x log 10 = 0.025 min-1 16. (d) The status of renal function impairment can be expressed by creatinine clearance. ClT = ClH + ClR where, ClT = Total body clearance ClH = Hepatic clearance

ClR = Renal clearance 2100 = 300 + ClR ClR = 1800 ml/hr = 30 ml/min The normal creatinine clearance generally lies between 80 to 120 ml/min. A creatinine clearance in patient is 30 ml/min which will be considered severely impaired. 17. (c) Blood serum freezes at 0.520 C, and all solutions having this freezing point are isotonic with blood serum. 0.9% sodium chloride have the same freezing point that of blood serum. FP provides by 1% Boric acid = -0.29o C FP of blood = - 0.52o C FP (needed) by NaCl = (0.52-0.29) = 0.23o C Now as we know that FP provides by 1% NaCl would be -0.58o C therefore one can say, For FP 0.58o needs 1 % NaCl For FP 0.23o needs ? = (0.23 x 1)/0.58 = 0.396 % NaCl 0.396 gm of NaCl/ 100cc. The amount of NaCl needed for 250cc, = (250 x 0.396)/100 = 0.991 gm NaCl = 991 mg

Sample Questions 1. Benzyl alcohol is classified as: a. Emulsifying agent b. Preservative c. Diluent d. Suspending agent 2. Cold cream is an example of: a. Suspension b. O/W emulsion c. W/O emulsion d. O/W/O emulsion 3. Which of the following is an example of an oligosaccharide? a. Glucose b. Sucrose

c. Starch d. Glycogen 4. Which pyrimidine base is found only in RNA? a. Cytosine b. Thymine c. Uracil d. Adenine 5. The deviation of data from its mean is generally described by: a. The average b. The standard deviation c. The precision d. The accuracy 6. The reproducibility of results of a number of experiments is generally known as: a. Precision b. Bias c. Accuracy d. Closelessness 7. Which of the following drugs is an angiotensin receptor antagonist ? a. Lisinopril b. Losartan c. Methyldopa d. Captopril 8. The rate of sedimentation is independent of : a. The viscosity of dispersion medium. b. The diameter of suspended particles. c. The difference in densities between dispersed medium and dispersed phase. d. The lipophilic nature of particles. 9. A patient with acute hypercapnia should be treated with which of the following ? a. Doxapram b. Dopamine c. Disopyramide

d. Ipecac 10. Which of the following is NOT an example of a live attenuated vaccine ? a. Measles b. Diphtheria c. Rubella d. Mumps 11. Corlopam (Feoldopam) is indicated for short-term (up to 48 hours) management of severe hypertension. It is classified a(n) a Alpha-1 receptors agonist. b Beta-2 receptor agonist c Dopamine-D1 receptor agonist d Histamine-H1 receptor agonist 12. Which of the following ratios is the best indicator of a pharmacy’s profitability ? a. Net profit to net sales b. Net profit to net worth c. Net profit to total asset d. Net profit to inventory 13. Which of the following ratios generally indicates the efficiency of a pharmacy ? a. Net profit to total assets. b. Inventory turnover rate c. Capitalization of net profit d. Net profit to net sales 14. The molecular geometry of a CH4 (methane) molecule is: a. Linear b. Angular c. Tetrahedral d. Trigonal bipyramidal 15. The transfer of molecules from a solid phase directly to a vapor phase is known as: a. Melting b. Sublimation

c. Freezing d. Evaporation 16. As with most menopause symptoms, hot flashes are due to a. Estrogen deficiency b. Estrogen excess c. Progesterone deficiency d. Progesterone excess 17. The symptoms of BPH are caused by a. pressure exerted by the prostate gland on urethra b. relaxation of bladder muscles c. shrinkage of the prostate gland d. relaxation of the prostate gland muscles 18. Which of the following TCA is used in the treatment of nocturnal enuresis? a. Doxepine b. Imipramine c. Sertraline d. Amoxapine ANSWER 1 (b) Benzyl alcohol is classified as a preservative. Preservatives prevent the growth of microorganisms and prevent deterioration of pharmaceutical dosage forms. The ideal preservative must have the following characteristics: It must be effective against a broad spectrum of microorganisms. It must be stable for the lifetime of the product. It must be nontoxic, soluble, palatable in test and odor and compatible with other ingredients in the formulation. Commonly used preservatives: * phenol * benzoic acid * benzyl alcohol * chlorobutanol * thiomersal * benzalkonium * cresol * cetylpyridinium ANSWER 2 (c) Cold cream is an example of W/O emulsion. It is a biphasic liquid dosage form, in which disperse phase and the dispersion medium are liquids. Emulsion is classified by five different categories: Water in Oil (W/O) : Oil is continuous phase and water is a disperse phase, i.e. lotions and liniments.

Oil in water (O/W) : Water is continuous phase and oil is a dispersed phase i.e. most of the oral emulsions to unmask the oil taste of a medication. Microemulsion : Unlike emulsions, microemulsion is a transparent with a small particle size. It is believed to be thermodynamically stable. The particle size of microemulsion lies between 10 to 200 nm. It is generally used for the solubilization of the drug in pharmaceutical dosage form. Nanoparticles : As the name suggests, the particle size of this kind of emulsion is limited to nanograms. They are useful for the preparation of globulins and toxoids. Tetanus toxoid and human immunoglobulin G are examples of nanoparticles emulsion. Multiple emulsions : Water in Oil in ware (W/O/W), Oil in water in Oil (O/W/O). The w/o/w emulsions are generally more preferable for preparation of various pharmaceutical dosage forms. They are used to prolong the duration of action of various drugs, to localize drug in the body and to prepare cosmetics. ANSWER 3 (b) Sucrose is an example of Oligosaccharide. It consists of a short chain of monosaccharide. It consists of one molecule of glucose and one molecule of fructose.Carbohydrates can be divided into three categories : Monosaccharide, Oligosaccharide and Polysaccharide. Monosaccharides : They are simple sugar such as glucose and fructose. Oligosaccharides : Consists of a small chain of monosaccharides. i.e. sucrose, maltose and lactose. They have to degraded into simple sugar in order to be absorb from the intestine. Degradation of sucrose gives one molecule of glucose and fructose, degradation of maltose gives two molecules of glucose, and degradation of lactose gives each molecule of galactose and glucose. Polysaccharides : They consist of long chains of monosaccharides i.e. starch and glycogen ANSWER 4 (c) Uracil. It is a pyrimidine base that only found on RNA. Nucleotides are the building blocks of the nucleic acid. Purines and pyrimidines bases bind to ribose to form nucleoside, which when binded to phosphoric acid forms the nucleotides. ANSWER 5 (b) The deviation of data from its mean or average is defined as standard deviation. The reproducibility of the series of measurements is known as precision. Accuracy is defined as closeness of measurements to the true value. ANSWER 6 (a) Precision. ANSWER 7 (b) Losartan.

ANSWER 8 (d) The relation of the rate of sedimentation with various parameters can be expressed by Stoke’s law. V = 2r2 (P1 - P2) g/9n V = velocity of sedimentation in cm/sec r = radius of the particles in cm P1 = density of disperse phase in g/cm3 P2 = density of dispersion medium in g/cm3 n = viscosity of dispersion medium g = gravity acceleration 980.7 cm/sec2 The rate of sedimentation is independent of the lipophilic nature of particles. ANSWER 9 (a) Doxapram is indicated as the respiratory stimulant agent in postanesthesia and in chronic obstructive pulmonary disease associated with acute hypercapnia. The respiratory stimulant to effect of this agent is attributed to its ability to stimulate the respiratory center in the medulla via carotid chemoreceptors. Ipecac is widely used as an emetic in accidental poisoning. It is also used as an expectorant. Dopamine is formed by the decarboxylation of 3,4-dihydroxyphenylalanine (DOPA). It is a precursor to noradrenalin and is also itself a neurotransmitter in CNS. It is indicated for treatment of cardiac shock. The vasodilation offered by dopamine is very important in drawing the blood in the kidney and small bowel during an ischemic attack. The diuretic property of dopamine helps to preserve the renal tubules. The cardiac stimulation improves the deteriorated cardiac function. Hypotension is a principal adverse effect of the drug. Disopyramide is classified as a class IA antiarrhythmic agent. It has profound anticholinergic side effects with severe A.V. node suppression properties. It should be carefully used in patients with congestive heart failure with glaucoma and urinary hesistancy. The major adverse effects reported are dry mouth, constipation, urinary retention and blurred vision. ANSWER 10 (b) Diptheria is an example of a killed inactivated vaccine. Measles, Mumps and Rubella are examples of live attenuated (live organism with reduced disease producing capacity) vaccines. Live attenuated vaccines should never be administered to an AIDS patient. ANSWER 11 (c) Corlopam (Feoldopam) is indicated for short-term (up to 48 hours) management of severe hypertension when rapid but quickly reversible, emergency reduction of blood pressure is clinically required. It is an agonist for Dopamine-D1 receptors.

ANSWER 12 (b) Net profit to net worth ratio is the best indicator of a pharmacy’s profitability, because it compares the net profit to net investment in the pharmacy. ANSWER 13 (b) Inventory turnover rate generally describes the efficiency of a pharmacy. It is generally calculated by dividing the cost of the goods sold by the average of beginning and ending inventory. ANSWER 14 (c) The molecular geometry of the Methane is tetrahedral. Below are examples of molecules with their possible geometry. Name Geometry BeCl2 Linear BF3 Trigonal planar SO2 Angular CH4 Tetrahedral NH3 Trigonal Pyramidal PCl543 5 Trigonal Bipyradimal ANSWER 15 (b) Sublimation. ANSWER 16 (a) Estrogen deficiency is the major cause for hot flashes. ANSWER 17 (a) The prostate gland is located below the bladder in men. It surrounds the urethra, which is a tube that drains urine from the bladder. Due to enlargement and tightening of muscles of the prostate gland, pressure is exerted on the urethra. The squeezing of the urethra results in slow flow of the urine from the bladder; which apparently causes the symptoms of BPH. Symptoms of BPH: * a weak or interrupted stream when urinating * a feeling that you cannot empty your bladder completely * a feeling of delay when you start to urinate * a need to urinate often, especially at night * a feeling that you must urinate right away ANSWER 18 (b) Imipramine is TCA mainly indicated for the treatment of nocturial enuresis. The M/A of TCA in the treatment of nocturial enuresis has been questioned. Desmopressin (Vasopressin) is a synthetic analog of endogenous human antidiuretic hormone also indicated for the treatment of nocturial enuresis.