Pharmaceutical Sciences & Calculations Flashcards

A patient requires 250 mg of amoxicillin. The suspension available is 125 mg/5 mL. What volume should be dispensed?

Answer: 10 mL

250 mg ÷ 125 mg × 5 mL = 10 mL. This is a standard concentration calculation.

What is the percentage concentration (w/v) of a solution containing 2 g of drug in 250 mL?

Answer: 0.8% w/v

2 g in 250 mL = 2/250 × 100 = 0.8% w/v. Percentage w/v = grams per 100 mL.

A prescription requires 0.5% w/v hydrocortisone cream in 50 g. How many milligrams of hydrocortisone are needed?

Answer: 250 mg

0.5% w/w means 0.5 g per 100 g. In 50 g: 0.5 × 50/100 = 0.25 g = 250 mg.

Which route of administration avoids first-pass metabolism most effectively?

Answer: Intravenous

Intravenous administration delivers drug directly into systemic circulation, completely bypassing first-pass hepatic metabolism.

What does a drug's half-life determine?

Answer: Time to reach steady state

Steady state is reached after approximately 4–5 half-lives. Half-life does not directly determine Cmax, Vd, or bioavailability.

Which formulation type is designed to release drug over an extended period to reduce dosing frequency?

Answer: Modified-release tablet

Modified-release (MR) formulations control the rate of drug release to maintain therapeutic levels over a longer period, reducing dosing frequency.