PSI Pharmaceutical Sciences 4 — Questions and Answers
Question 1: Which process converts a prodrug to its active form?
- Bioactivation (Correct answer)
- Glucuronidation
- Renal filtration
- Protein binding
Correct answer: Bioactivation
Bioactivation is metabolic conversion of an inactive prodrug to its pharmacologically active metabolite. Example: enalapril → enalaprilat; codeine → morphine (via CYP2D6).
Question 2: Which preservative is commonly used in multi-dose eye drop formulations?
- Benzalkonium chloride (Correct answer)
- Chlorhexidine
- Benzyl alcohol
- Phenol
Correct answer: Benzalkonium chloride
Benzalkonium chloride (BAK) is the most widely used preservative in ophthalmic preparations. It disrupts bacterial cell membranes but can cause ocular surface toxicity with prolonged use.
Question 3: Zero-order release from a drug delivery system means drug is released at:
- A constant rate independent of concentration (Correct answer)
- A rate proportional to drug remaining
- A rapidly decreasing rate
- A rate dependent on pH
Correct answer: A constant rate independent of concentration
Zero-order release provides a constant amount of drug per unit time, maintaining steady plasma levels. This is ideal for potent drugs with narrow therapeutic windows.
Question 4: Which test ensures that a parenteral product is free of fever-causing bacterial products?
- Pyrogen/endotoxin test (Correct answer)
- Sterility test
- Particulate matter test
- pH test
Correct answer: Pyrogen/endotoxin test
The pyrogen/endotoxin test (LAL test — Limulus Amebocyte Lysate) detects bacterial endotoxins that cause fever when injected. It is a critical quality test for parenteral products.
Question 5: Lyophilisation (freeze-drying) is used primarily to improve the stability of:
- Thermolabile or moisture-sensitive drugs (Correct answer)
- Highly lipophilic drugs
- Enteric-coated tablets
- Controlled-release matrix tablets
Correct answer: Thermolabile or moisture-sensitive drugs
Freeze-drying removes water by sublimation under vacuum, preserving the drug structure without heat. It is used for biologicals, vaccines and unstable drugs.
Question 6: Which term describes the fraction of administered drug that reaches systemic circulation unchanged?
- Bioavailability (Correct answer)
- Clearance
- Half-life
- Volume of distribution
Correct answer: Bioavailability
Bioavailability (F) is the proportion of dose reaching systemic circulation in active form. IV = 100%; oral bioavailability is reduced by incomplete absorption and first-pass metabolism.
PSI Pharmaceutical Sciences 4
Which process converts a prodrug to its active form?