GPhC Pharmaceutical Sciences & Calculations 2 — Questions and Answers
Question 1: A patient weighing 70 kg requires a drug at 5 mg/kg/day in two divided doses. What is each dose?
- 175 mg (Correct answer)
- 350 mg
- 87.5 mg
- 140 mg
Correct answer: 175 mg
Total daily dose = 70 × 5 = 350 mg. Divided into 2 doses: 350 ÷ 2 = 175 mg per dose.
Question 2: An infusion of 500 mg in 250 mL is running at 50 mL/hour. What is the rate in mg/hour?
- 100 mg/hour (Correct answer)
- 50 mg/hour
- 200 mg/hour
- 25 mg/hour
Correct answer: 100 mg/hour
Concentration = 500/250 = 2 mg/mL. Rate = 2 mg/mL × 50 mL/hour = 100 mg/hour.
Question 3: Which excipient acts as a preservative in multi-dose eye drops?
- Benzalkonium chloride (Correct answer)
- Hydroxypropyl methylcellulose
- Sodium chloride
- Povidone
Correct answer: Benzalkonium chloride
Benzalkonium chloride (BAC) is the most commonly used preservative in multi-dose ophthalmic preparations. It prevents microbial contamination.
Question 4: What is the purpose of an enteric coating on a tablet?
- To prevent dissolution in gastric acid (Correct answer)
- To mask unpleasant taste
- To improve appearance
- To speed up drug release
Correct answer: To prevent dissolution in gastric acid
Enteric coatings resist gastric acid and dissolve in the higher pH of the small intestine, protecting acid-labile drugs or preventing gastric irritation.
Question 5: A solution has a pH of 3. What does this indicate?
- Acidic solution (Correct answer)
- Neutral solution
- Alkaline solution
- Buffered solution
Correct answer: Acidic solution
pH below 7 indicates an acidic solution. pH 7 is neutral; above 7 is alkaline. pH 3 is strongly acidic.
Question 6: Which property of a drug most influences its ability to cross the blood-brain barrier?
- Lipophilicity (Correct answer)
- Molecular weight only
- Protein binding
- Renal clearance
Correct answer: Lipophilicity
Lipophilic (fat-soluble) drugs cross the blood-brain barrier more readily because the barrier is composed mainly of lipid bilayer membranes.
GPhC Pharmaceutical Sciences & Calculations 2
A patient weighing 70 kg requires a drug at 5 mg/kg/day in two divided doses.
What is each dose?