Pharmacy Sterile and Non Sterile Compounding -Calculations

If a 3-year-old child weighing 33 lb accidentally ingested 20 81-mg aspirin tablets, how much aspirin did the child ingest on a milligram per kilogram basis?

108 mg/kg 33/ 2.2 = 15 kg 20 x 81mg/tab = 1620 mg 1620 mg/15 kg = X mg / 1 kg

You are asked to prepare 52 mL of a 28% Flagyl solution, and you have in stock 42 g/mL solution. How many milliliters of the 42 g/mL will you use?

0.35 mL 0.28 g/mL IS = 42g/mL, IV = X, FS = 0.28 g/mL, and FV = 52 mL

How many milligrams are in one tablet of Nitrostat 1/150 gr?

0.4 mg 1 gr is 65 mg 65 mg/1gr = xmg/ 1/150 gr

The drug vial contains 1,000,000 units of penicillin G. The label directions state: Add 2.3 mL of sterile water to the vial, 1.2 mL = 500,000 units. How many milliliters equal 200,000 units?

0.48 mL 500,000 units/ 1.2 mL = 200,000 units / X mL

What is the percent of a 1:200 (w/w) ointment?

0.5% 1/200 x 100

The physician ordered 0.725 mg of droperidol (Inapsine) IV stat. The vial reads 2.5 mg in 2 mL. Calculate the amount of drug you will administer to this patient in milliliters.

0.58 mL 2.5 mg / 2 mL - 0.725 mg / X mL

How many milliliters of aminophylline injection containing 250 mg in each 10 mL should be used in filling a medication order calling for 15 mg of aminophylline?

0.6 mL 250 mg / 10 mL = 15 mg/ X mL

if 125 mL of liquid weighs 95 g, what is its specific gravity?

0.76 mL SG w/v 95/125

What is the specific gravity of a substance that weighs 60 g and occupies a volume of 75 mL?

0.8 SG = 60/75

1500 mL TPN solution is given IV at 75 mL/hr using an administration set with a drop factor of 20 gtt/mL. If the infusion starts at 0900 hours, when will it end?

0500 hr 1500 mL / 75 mL/hr = 20 mr. First bag 0900 will last 20 hours 0900 + 2000 hr - 2400 hr/day + 0500 hr next day

How many milliliters of a 1/2% solution of gentian violet should be used in preparing 500 mL of a 1:100,000 solution?

1 mL dilution 1:100,000 = 0.001% IS = 0.5%, IV = X, FS=1/100,000 and FV = 500 mL

How much metoclopramide 5 mg/mL is used to make 10 mL of 0.5 mg/ mL solution?

1 mL dilution IS = 5g/mL, IV = X, FS = 0.5 mg/mL, FV = 10 mL

A patient is to receive 25 units of the hormonal drug vasopressin (Pitressin) IM. If the label reads 50 units per 2 mL, how many milliliters will you administer to the patient?

1.0 mL 50 units/ 2 mL - 25 units / X mL

How many grams of NaC1 are in 250 mL of 1/2 NS (0.45%)?

1.125 g .0045 x 250 mL

a Patient is to receive a 100-mg dose of gentamicin. The medication is available in an 80-mg/mL vial. How many milliliters should the patient receive?

1.2 mL 80mg/mL = 100 mg/ X mL

You have a 2-mL ampule of caffeine. Na benzonatate containing gr viiss. If the physican orders gr v, how many milliliters will you dispense?

1.33 mL V= 5; VIISS = 7.5 7.5gr/2 mL = 5 gr/ XmL

RX: Carafate 400 mg/5 mL Cherry syrup 40 mL Sorbitol solution 40 mL Flavor qs Purified water ad 125 mL Sig: 5 mL tid How many 1-g Carafate tablets should be used in preparing the prescription?

10 1-g Carafate tablets 400 mg/5 mL = X mg/125 mL 10,000 mg total quantity / 1000 = 10

A drug has a concentration of 20 mg/mL. How many grams of the drug are in 1/2 L of the solution?

10 g 20 mg / 1000 0.5 mL x 1000 0.02g / 1 mL = Xg / 500 mL

You are asked to prepare 50 mL of a 1:100 rifampin suspension, and you have in stock a 1:20 rifampin suspension. How many milliliters of the 1:20 suspension will you need?

10 mL= IV IS = 1:20, IV = X FS = 1:100 and FV = 50mL

How many micrograms are in 1.0 mL of a 1:100 solution?

10,000 mcg 1:100 = 0.01(g=mL) X 1000 = (1000mg/1g)(1000 mcg/1mg)

Convert 40 C to F

104 40 x 1.8 + 32

A pharmacist has received an order to prepare 1 lb of 5% (w/w) salicylic acid ointment. How much salicylic acid is needed to prepare this ointment?

2.27 g 1 lb = 454 g x 0.05

How many grams of silver nitrate are needed to make 1 L of a 0.25% solution?

2.5 g. 1 L = 1000 mL x .0025

If 100 mL of 25% (w/v) Solution is diluted to 1 L, what will be the percentage strength (w/v)?

2.5% IS IV = FS FV 1L = 1000 mL IS= 25% IV= 100 mL FS = X FV= 1000 mL

Prepare 300 mL of 7.5% dextrose using SWFI and D20W. How much of each is needed?

20% - 112.5 ml; SWFI -187.5 mL alligation

How much 10% dextrose solution and 20% dextrose solution should be mixed to prepare 1 l of 12.5 % dextrose solution?

20% - 250 mL; 10% - 750 mL alligation

If a physician prescribed cephalexin 250 mg qid for 10 days, how many milliliters of cephalexin oral suspension containing 250 mg/tsp should be dispensed?

200 mL 250 mg X 4 X 10 5mL x 4 x 10 days

The prescriber ordered atropine sulfate 0.2 mg SC q6h prn. What is the equivalent dose in micrograms?

200 mcg 0.2 mg x 1000

If a child weighs 60 lb and the adult dose is 500 mg, how many milligrams should the child receive?

200 mg 60 / 150 x 500 mg Clark's Rule

How much water should be added to 1 quart of 70% isopropyl alcohol to prepare a 20% solution for soaking sponges?

2400 mL dilution IS = 70%, IV = 960 mL, FS = 20% and FV = X 3360 mL - 960 mL = 2400 mL

An IV piggyback of pentamidine isethionate containing 300 mg of drug in 150 ml of D5W is to be infused over 2 hr. The IV set is calibrated to deliver 20 gtt/mL. How many drops per minute should be administered?

25 gtt/min 150 mL/2hr + 75 mL/hr X 20 gtt/mL X 60 min = 25 gtt/min

How may milliliters of a 1:50 (w/v) stock solution of a chemical should be used to prepare 2 L of a 1:4000 (w/v) solution?

25 mL. = IV IS = 1:50, IV = X, FS = 1:4000, and FV = 2000 mL

If a child is 4 years old and the adult dose of medication is 100 mg, how much medication should the child receive?

25 mg 4 / 4+12 X 100 mg Young's rule

The physician has ordered Coumadin 5 mg to be taken on Mon, Wed, and Fri. On Tues, Thurs, Sat and Sun, the patient is to receive 2 1/2 mg. How many milligrams will the patient take in 1 week?

25 mg 5 mg x 3 days; 2 1/2 mg x 4 days

How many milliliters of a 2.5% (w/v) chlorpromazine hydrochloride injection and how many milliliters of a 0.9% (w/v) sodium chloride injection should be used to prepare 500 mL of a 1.25% (w/v) chlorpromazine hydrochloride injection?

25% - 109 mL; 0.9 - 391 mL

Make 30 mL of a vitamin B12 dilution with a concentration of 100 mcg/ mL from a stock solution of 1 mg/mL. How much vitamin B 12 and diluent are needed?

3 ml of vitamin B12 and 27 mL of dilution IS = 1mg/mL IV = X, FS = 100 mcg/mL, and FV = 30 mL 30 mL - 3 mL = 27 mL

The order is for K-Lor 60 mEq PO stat. Each packet contains 20 mEq. How many packets of K-Lor

3 packets 20 mEq/ 1 = 60 mEq/ X

How many grams of antipyrine should be used in preparing the following prescription? Rx Antipyrine 5% Glycerin Ad 60

3.0 g of antipyrine FV - FS = IV - IS .05 x 60 g

The prescriber ordered 175,000 units of urokinase IVPB. The vial directions read: "Add 4.2 mL to vial and each mL will contain 50,000 units. "How many milliliters will you prepare?

3.5 mL 50,000 units / 1 ml = 175,000 units / X mL

Prepare 15 ml of cefazolin dilution 50 mg / mL from a stock of 1 g/5 mL. How many milliliters of the diluent and cefazolin will be needed?

3.75mL of cefazolin; 11.25 mL of dilution IS = 1g/5 mL, IV = X, FS = 50mg/mL, FV = 15 mL 15 mL - 3.75mL = 11.25 mL

An initial heparin dose of not less than 150 units/ kg of body weight has been recommended for open heart surgery. How many milliliters of an injection containing 5000 heparin units per milliliter should be administered to a 280 lb-patient?

3.82 mL 280 / 2.2 = 127.27 kg X 150 units/kg = 19,095 units 5000 units/ mL ; 19,095 units/ X mL = 3.82 mL

You are asked to prepare 36 mL of a 1:4 Bactrim solution, and you have in stock 30% solution, How many milliliters of the 30% solution will you use?

30 mL 1:4 =25% IS = 30%, IV = X, 25%, and FV = 36 mL

How many milliliters of a 3% (w/v) solution will be necessary to make 6 oz of a 1:200 solution?

30 mL IS IV = FS FV IS = 3% IV = X FS 1:200 (0.5%) FV 6 oz x 30 mL = 180mL

How many grams are in 1 L of a 1:200 solution?

5 g 1:200 = 0.05 x 1 L = 1000 mL

If a child weighs 50 lb and the adult dose is 1 tbsp, how many milliliters should the child receive?

5 mL 50 / 150 X 15 mL Clark's Rule

If 500 mL of an IV solution contains 0.1 g of a drug, at what flow rate in milliliters per minute should the solution be administered to provide 1 mg/min of the drug?

5 mL/min 500 mL / 100 min + 5 mL/min

In what proportion should 5% and 1% hydrocortisone ointments be mixed to prepare a 2.5% ointment?

5% - 1.5 parts; 1% - 2.5 parts alligation

The prescriber ordered 0.05 mg of Sandostatin PO, a hormone. How many micrograms are in this dose?

50 mcg 0.05 mg x 1000

If a child is 36 months old and the adult dose is 250 mg, how much medication should the child receive?

50 mg 36 mo / 12 mo/ year = 3 year or 3 / 3+12 x 250 mg Young's rule

How many colchicine tablets each containing 600 mcg may be prepared from 30 g of colchincine?

50,000 tablets 30 g x 1,000,000 - 30,000,000mcg / 600 mcg

A prefilled syringe of furosemide contains 20 mg of drug in 2 mL of solution. How many micrograms of drug would be administered by an injection of 0.5 mL of the solution?

5000 mcg 20 mg / 2 mL - X mg / 0.5 mL x 1000

How many grams of Eucerin should be added to 4 oz of a 10% ointment to make a 7% ointment?

51 g IS IW = FS FW IS = 10% IW = 120g FS = 7% FW = X

You are to prepare a dose of 300 mg and the tablets are available in 75-mg strength. How many tablets will the pharmacist need to dispense if the patient is to take 300 mg bid for 1 week?

56 tablets 75 mg dose/1 tablet = 300 mg dose / X tablets = 4 4 x 2 x 7

How many grams of reserpine would be required to make 25,000 tablets, each containing 250 mcg of reserpine?

6.25g 250 mcg/tablet x 25,000 tablets 1,000,000 mcg/g

You receive an order for 125 mL of 4% acetic acid solution and you have in stock 75% acetic acid solution. How many milliliters of the 75% solution will you need?

6.67 mL IS IV = FS FV IS = 75% IV = X FS = 4% FV = 125mL

How many 600-mg ibuprofen tablets will be needed to make 8 oz of a 15% ointment?

60 tablets 8 oz is approximately 240g 240 g X .15 = 36 g or 36,000 mg/ 600 mg

What is the total volume that will be delivered if a patient receives normal saline solution at 25 mL/hr for 24 hr?

600 mL 25 mL/hr x 24 hr

A physician orders 3 L D5W to be administered over 24 hr. How many drops per minute will be delivered using an administration set calibrated to deliver 30 drops per milliliter?

62 gtt/min 120 mL/hr X 30 gtt/mL x 60 min = 62 gtt/min

Medication: solu-Cortef 250 mg a. Fluid volume: 250 mL b. Time of infusion: 4 hr c. How many ml/hr? How many mg/hr/

62.5 mL 250 mL / 4 hr = 62.5 mL/hr 250 mg/40 hr = 62.5 mg

A stock bottle of Lugol solution contains 2 oz from the original pint bottle. The pharmacy technician is able to prepare four 8-oz bottles of a more dilute 4% solution. What was the original percentage strength of the Lugol solution?

64% IS IV = FS FV IS = X IV = 2 oz FS - 4% FV = 32 oz

A pediatric patient is to be given a 70-mg dose of Dilantin by administration of an oral suspension containing 50 mg of Dilantin per 5 mL. How many milliliters of the suspension must be administered?

7 mL 50 mg / 5 mL = 70 mg / X mL

Convert 45 F to C

7.2 45-32 / 1.8

A 25-lb child is to receive 4 mg of phenytoin per kg of body weight as an anticonvulsant. How many milliliters of pediatric phenytoin suspension containing 30 mg/5 ml should the child receive?

7.5 mL 25 / 2.2 = 11.36 x 4 = 45.45 / X mL 30 mg/ 5 mL

A 20% KCI solution has a strength of 40 mEq/tbsp. How many milliliters need to be dispensed for the patient to receive 20 mEq?

7.5 mL 40 mEq/tbsp. = 20 mEq/ X mL

How many milliliters of a 1;2000 iodine solution an d a7.5% iodine solution are needed to make 120 ml of a 3.5% solution?

7.5% 55.6 mL; 1:2000 64.4 mL

How many milliliters of water should be added to 500 mL of a 1:2000 (w/v) wolution to make a 1:5000 (w/v) solution?

750 mL dilution IS = 1:2000, IV = 500 mL, FS = 1:5000 and FV = X 1250mL - 500 mL = 750 mL of dilution

A volume of fluid weighs 80 g and has a specific gravity: of 1.05. What is the volume?

76 mL SG 1.05 = 80/X

You are asked to prepare 80 mL of a 72% lidocaine solution, and you have in stock a 75% solution. How many milliliters of the 75% solution will you use?

76.8 mL IS IV = FS FV IS = 75% IV = X FS = 72% FV = 80 mL

Convert 25 C to F

77 25 x 1.8 + 32

If 1000 mL at 20 drops/min is administered using a 15-drop set, what is the flow rate in milliliters per hour?

80 mL/hr. 20 gtt/min / 15 gtt/mL X 60 min = 80 mL/hr

If the dose of a drug is 150 mcg, how many doses are contained in 0.120 g?

800 doses .0.120g x 1,000,000 = 120,000mcg / 150 mcg

Cyclosporine is an immunosuppressive agent administered before and after organ transplantation at a single dose of 15 mg/kg. How many milliliters OF A 50-mL BOTTLE containing 100 mg of cyclosporine per milliliter would be administered to a 140 lb kidney transplant patient?

9.54 mL 140 / 2.2 = 63.63 X 15 mg = 954.54 100 mg/ mL = 954.54 / X mL

You are asked to prepare 125 mL of a 1:8 nystatin suspension, and you have in stock a 1:6 solution. How many milliliters of the 1:6 bystatin solution will you need?

91.94 mL= IV IF = 1:6, IV= X, FS = 1:8 and FV = 125 mL

In what proportions should alcohols of 95% and 50% strengths be mixed to prepare 250 ml of a 70% alcohol solution?

95 % 5:9; 50% 4:9

How many milliliters of a 5% stock solution are needed to prepare 1 pint of a solution containing 100 mg of the chemical per liter?

960 mL 100mg/1000mL to a percent which is 0.01%

Prepare 500 mL of D12.5W. You have on hand D5W, D10W, and D20W. How much of which two solutions will you use?

alligation 20% and 5% - 250mL; 20% - 125 mL, 10% - 375 mL

The antiviral ophthalmic drug fomivirsen sodium (Vitravene) has been ordered by the physician 330 mcg. The vial is labeled 6.6 mg/mL. How many milliliters contain the prescribed dose?

0.05 mL 330 mcg / 1000 6.6 mg/ mL = 0.660mg / X mL

An IV piggyback of enalapril maleate containing 10 mg of drug in 50 ml of 0.9% sodium chloride injection is to be infused over 1 hour. The IV set is calibrated to deliver 15 gtt/mL. How many drops per minute should be administered?

12 gtt/min 50 mL/hr X 15 gtt/mL X 60 min = 12 gtt/min

The dose of a drug is 500 mcg/kg of body weight. How many milligrams should be given to a child weighing 55 lb.

12.5 mg 55 / 2.2 x 500 mcg / 1000

How many grams of a 2.5% hydrocortisone cream should be mixed with 240 g of a 0.25% hydrocortisone cream to make a 1% cream?

120 g alligation 360 g - 240 g = 120 g

How many grams are in 100 mL of a liquid if its specific gravity is 1.25?

125 g SG 1.25 = X/100

Calculate the flow rate to be used to infuse 1000 mL of NS over 8 hours if the set delivers 10 gtt/ mL.

125 mL/hr 1000 mL / 8 hrs

If a child weighs 45 lb and the adult dose is 50 mg, how much medication should the child receive?

15 mg 45/150 x 50 mg Clarks Rule

An IV piggyback of lincomycin containing 1 g of drug in 100 mL is to be infused over 1 1/2 hours. The IV set is calibrated to deliver 15 gtt/mL. How many drops per minute will the patient receive?

16 gtt,/min 1000 mL / 1.5 hr = 66 mL/hr X 15 gtt/mL X 60 min = 16 gtt/min

If a child weighs 15 kg and the adult dose is 75 mg, how many milligrams should the child receive?

16.5 mg 15 x 2.2 = 33 (33/150) x 75 mg Clark's Rule

The usual pediatric dose of cefazolin sodium is 25 mg/kg/day divided equally into three doses. What would be the single dose in milligrams for a child weighing 44 lb?

166.67 mg/kg 44 / 2.2 = 20 kg X 25 mg = 500 mg / 3 doses

If a child is 2 1/2 years old and the adult dose is 100 mg, how much medication should the child receive?

17 mg 2.5 / 2.5 + 12 x 100 mg Young's rule

Convert 65 F to C

18.33 65-32 / 1.8

The usual dose range of dimercaprol is 2.5 mg to 5 mg/kg of body weight. What would be the dose range for a person weighing 165 lb?

187.5 to 375 mg 165 / 2.2 = 75 x 2.5 mg- 75 x 5 mg

What will be the rate in gtt/min if a patient receives 1 L of an IV fluid over an 8-hr period if the drop factor = 15 gtt/mL

31 gtt/min 1000 mL / 8 hr X 15 gtt/mL X 60 min = 31 gtt/min

A dose of antacid is 1 tbsp. How many doses can be prepared from a pint bottle?

32 doses 1 Tbsp = 15 mL 1 pt = 480 mL 15 mL/1 dose = 480 mL / X doses

You are asked to prepare 50 mL of a 1:3 folic acid solution, and you have in stock a 1:2 solution. How many milliliters of the 1:2 solution will you use?

33 mL = IV IS = 1:2, IV - X, FS = 1:3 and FV = 50mL

How many milliliters of a 95% (v/v) alcohol should be used in preparing 1 pint of 75% (v/v) solution?

379 mL IS = 95%, IV = X, FS = 75%, and FV is 480 mL

What is the percent of a 1:25 (w/V) solution?

4% 1/25 x 100

If a pharmacist adds 3g of hydrocortisone to 120 g of a 5% hydrocortisone cream, what is the final percentage strength of hydrocortisone in the product?

4.88% IS IW= FS FW IS =5% IW = 120g FS = X FW = 123 g

How many milliliters of IV fluid will a patient receive if infused at the rate of 120 mL/hr over 3 1/2 hr?

420 mL 120 mL/hr x 3 1/2 hr = 420 mL

The formula for a buffer solution contains 1.24% (w/v) of boric acid. How many milliliters of a 10% (w/v) boric acid solution should be used to obtain the boric acid needed in preparing 1 gal of buffer solution?

476 mL IS IV = FS FV 1 gallon = 3840 mL IS = 10% IV = X FS = 1.24% FV = 3840mL

How many chloramphenicol capsules each containing 250 mg of chloramphenicol are needed to provide 25 mg/kg/day of body weight for 1 week for a person weighing 154 lb?

49 capsules 154 / 2.2 X 25mg X 7 days / 250 mg per capsule

1 L NS is to be administered over 24 hr. The administration set to be used has a DF of 15 gtt/mL. What is the rate of infusion in a. mL/hr b. gtt/min

a. 41 mL/hr 1000 mL/24 hr = 41 hr b. 10 gtt/min 41 ml/hr X 15 gtt/ mL X 60 min = 10gtt/min

RX: Hydrocodone bitartrate 0.2 g Phenacetin 3.6 g Aspirin 6.0 g Caffeine 0.6 g M ft caps no 24 Sig I cap tid prn pain a. How many milligrams of hydrocodone bitartrate would be contained in each capsule? b. What is the total weight, in milligrams, of the ingredients in each capsule? c. How many milligrams of caffeine would be taken daily?

a. 8.33 mg/capsule 0.2 g/24 capsules = 0.00833 g capsule X 1000 = 8.33 mg/cap b. 430 mg per capsule 10.4 g / 24 capsules. 0.43 g X 1000 = 430 mg/capsule c. 75 mg. 0.6 g / 24 capsules= 0.025 g of caffeine/capsule X 1000 = 25 mg 25 mg of caffeine/capsule X 3 capsules = 75 mg