PEBC Pharmaceutical Calculations 4

Question 1

A patient requires an IV infusion of dopamine at 5 mcg/kg/min. The patient weighs 80 kg. The dopamine concentration available is 400 mg in 250 mL D5W. What is the infusion rate in mL/hr?

Accepted Answer

15 mL/hr

Answer

Dose = 5 mcg/kg/min × 80 kg = 400 mcg/min = 24,000 mcg/hr = 24 mg/hr; concentration = 400 mg/250 mL = 1.6 mg/mL; rate = 24 mg/hr ÷ 1.6 mg/mL = 15 mL/hr.

Question 2

A prescription calls for 2% hydrocortisone cream. You have 1% and 5% hydrocortisone creams in stock. Using the alligation method, what ratio of 1% to 5% cream should be mixed?

Accepted Answer

3 parts 1% : 1 part 5%

Answer

By alligation: 1% gives (5−2)=3 parts and 5% gives (2−1)=1 part, so the ratio of 1%:5% is 3:1.

Question 3

A child weighing 22 kg needs amoxicillin 40 mg/kg/day in 3 divided doses. The suspension available is 250 mg/5 mL. How many mL per dose should the child receive?

Accepted Answer

5.9 mL

Answer

Total daily dose = 40 mg/kg × 22 kg = 880 mg/day; per dose = 880 ÷ 3 ≈ 293 mg; volume = (293 mg ÷ 250 mg) × 5 mL ≈ 5.9 mL.

Question 4

How many grams of dextrose are contained in 500 mL of D10W?

Accepted Answer

50 g

Answer

D10W means 10 g dextrose per 100 mL; 500 mL × (10 g/100 mL) = 50 g.

Question 5

A pharmacist needs to prepare 240 mL of a 0.9% NaCl solution using water for injection and a 23.4% NaCl concentrate. How many mL of the 23.4% concentrate is needed?

Accepted Answer

9.2 mL

Answer

Using C1V1 = C2V2: 23.4% × V1 = 0.9% × 240 mL; V1 = 216/23.4 ≈ 9.2 mL.

PEBC - Pharmacy Examining Board of Canada Practice Test

PEBC - Pharmacy Examining Board of Canada Practice Test

PEBC Pharmaceutical Calculations 4