GPhC Pharmaceutical Sciences & Calculations

Question 1

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

Accepted Answer

10 mL

Answer

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

Question 2

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

Accepted Answer

0.8% w/v

Answer

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

Question 3

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

Accepted Answer

250 mg

Answer

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

Question 4

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

Accepted Answer

Intravenous

Answer

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

Question 5

What does a drug's half-life determine?

Accepted Answer

Time to reach steady state

Answer

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

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