Pharmaceutical Calculations Flashcards

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)?

Answer: 737 mL

By alligation: parts of 95% = 70 − 0 = 70; total parts = 95; volume = (70/95) × 1000 ≈ 737 mL.

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?

Answer: 49 mL/min

(140 − 65) × 70 ÷ (72 × 1.5) = 5250 ÷ 108 ≈ 49 mL/min.

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?

Answer: 0.7 mL

Powder volume = final volume − diluent volume = 10 mL − 9.3 mL = 0.7 mL.

How many mL of a 10% stock solution are needed to prepare 500 mL of a 2% solution?

Answer: 100 mL

C1V1 = C2V2 → 10% × V1 = 2% × 500 mL → V1 = 1000/10 = 100 mL.

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?

Answer: 525 mg

Vd = 0.5 L/kg × 70 kg = 35 L; Loading dose = Cp × Vd = 15 mg/L × 35 L = 525 mg.

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?

Answer: 135 mg

Total dose = 75 mg/m² × 1.8 m² = 135 mg.

How many grams of zinc oxide are required to prepare 60 g of a 20% zinc oxide ointment?

Answer: 12 g

20% of 60 g = 0.20 × 60 = 12 g of zinc oxide.