Pharmaceutical Calculations Flashcards

A drug has a Vd of 0.5 L/kg and F = 1. What loading dose achieves a plasma concentration of 15 mg/L in a 70-kg patient?

Answer: 525 mg

LD = Vd × Cp ÷ F = (0.5 × 70) L × 15 mg/L = 525 mg.

A drug has an elimination rate constant of 0.1155 h⁻¹. What is its half-life?

Answer: 6 hours

t½ = 0.693 ÷ k = 0.693 ÷ 0.1155 = 6 hours.

Assuming first-order elimination, what percentage of a drug remains after 4 half-lives?

Answer: 6.25%

(1/2)⁴ = 1/16 = 6.25% remaining.

A solution contains 0.0005% w/v of an impurity. What is that in parts per million?

Answer: 5 ppm

1% = 10,000 ppm, so 0.0005% × 10,000 = 5 ppm.

250 mg of a drug is dissolved in enough water to make 50 mL. What is the % w/v concentration?

Answer: 0.5%

0.25 g ÷ 50 mL × 100 = 0.5% w/v.

How many kilocalories does 1 liter of D5W provide, using 3.4 kcal/g for dextrose monohydrate?

Answer: 170 kcal

D5W has 50 g dextrose per liter × 3.4 kcal/g = 170 kcal.

A 2 g vial of powder is reconstituted with 8.6 mL of diluent to a final volume of 10 mL. How many mL contain a 750 mg dose?

Answer: 3.75 mL

The final concentration is 2,000 mg ÷ 10 mL = 200 mg/mL, so 750 ÷ 200 = 3.75 mL.