PEBC Pharmaceutical Calculations 2 — Questions and Answers
Question 1: Using the alligation method, how many mL of 95% alcohol are needed to prepare 1000 mL of 70% alcohol (the other component being purified water)?
- 737 mL (Correct answer)
- 700 mL
- 650 mL
- 750 mL
Correct answer: 737 mL
By alligation: parts of 95% = 70 − 0 = 70; total parts = 95; volume = (70/95) × 1000 ≈ 737 mL.
Question 2: Using the Cockcroft-Gault equation [CrCl = (140 − age) × weight / (72 × SCr)], what is the estimated creatinine clearance for a 65-year-old male, 70 kg, with a serum creatinine of 1.5 mg/dL?
- 32 mL/min
- 49 mL/min (Correct answer)
- 54 mL/min
- 61 mL/min
Correct answer: 49 mL/min
(140 − 65) × 70 ÷ (72 × 1.5) = 5250 ÷ 108 ≈ 49 mL/min.
Question 3: A pharmacist reconstitutes a 1 g vial of antibiotic powder by adding 9.3 mL of sterile water to yield a final volume of 10 mL. What is the powder volume?
- 0.3 mL
- 0.5 mL
- 0.7 mL (Correct answer)
- 1.0 mL
Correct answer: 0.7 mL
Powder volume = final volume − diluent volume = 10 mL − 9.3 mL = 0.7 mL.
Question 4: How many mL of a 10% stock solution are needed to prepare 500 mL of a 2% solution?
- 50 mL
- 100 mL (Correct answer)
- 150 mL
- 200 mL
Correct answer: 100 mL
C1V1 = C2V2 → 10% × V1 = 2% × 500 mL → V1 = 1000/10 = 100 mL.
Question 5: A drug has a volume of distribution of 0.5 L/kg. A loading dose is required to achieve a target plasma concentration of 15 mg/L in a 70 kg patient. What is the loading dose?
- 262.5 mg
- 525 mg (Correct answer)
- 1050 mg
- 750 mg
Correct answer: 525 mg
Vd = 0.5 L/kg × 70 kg = 35 L; Loading dose = Cp × Vd = 15 mg/L × 35 L = 525 mg.
Question 6: A chemotherapy drug is dosed at 75 mg/m². A patient has a body surface area (BSA) of 1.8 m². What total dose should be administered?
- 100 mg
- 125 mg
- 135 mg (Correct answer)
- 150 mg
Correct answer: 135 mg
Total dose = 75 mg/m² × 1.8 m² = 135 mg.
Question 7: How many grams of zinc oxide are required to prepare 60 g of a 20% zinc oxide ointment?
- 6 g
- 12 g (Correct answer)
- 16 g
- 20 g
Correct answer: 12 g
20% of 60 g = 0.20 × 60 = 12 g of zinc oxide.
PEBC Pharmaceutical Calculations 2
Using the alligation method, how many mL of 95% alcohol are needed to prepare 1000 mL of 70% alcohol (the other component being purified water)?