GPhC Pharmaceutical Sciences & Calculations 1 — Questions and Answers
Question 1: A patient requires 250 mg of amoxicillin. The suspension available is 125 mg/5 mL. What volume should be dispensed?
- 10 mL (Correct answer)
- 5 mL
- 2.5 mL
- 15 mL
Correct answer: 10 mL
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?
- 0.8% w/v (Correct answer)
- 2% w/v
- 0.4% w/v
- 1% w/v
Correct answer: 0.8% w/v
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?
- 250 mg (Correct answer)
- 500 mg
- 50 mg
- 100 mg
Correct 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.
Question 4: Which route of administration avoids first-pass metabolism most effectively?
- Intravenous (Correct answer)
- Oral
- Sublingual
- Rectal
Correct answer: Intravenous
Intravenous administration delivers drug directly into systemic circulation, completely bypassing first-pass hepatic metabolism.
Question 5: What does a drug's half-life determine?
- Time to reach steady state (Correct answer)
- Peak plasma concentration
- Volume of distribution
- Bioavailability
Correct 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.
Question 6: Which formulation type is designed to release drug over an extended period to reduce dosing frequency?
- Modified-release tablet (Correct answer)
- Effervescent tablet
- Dispersible tablet
- Enteric-coated tablet
Correct 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.
GPhC Pharmaceutical Sciences & Calculations 1
A patient requires 250 mg of amoxicillin.
The suspension available is 125 mg/5 mL.
What volume should be dispensed?