GPhC Pharmaceutical Sciences & Calculations 4 — Questions and Answers
Question 1: What is the molecular basis of drug tolerance?
- Receptor downregulation (Correct answer)
- Increased renal excretion
- Reduced protein binding
- Enhanced gut absorption
Correct answer: Receptor downregulation
Tolerance often develops due to receptor downregulation — the number or sensitivity of receptors decreases with repeated drug exposure, reducing effect.
Question 2: Which type of emulsion is most suitable for intravenous administration?
- Oil-in-water (O/W) (Correct answer)
- Water-in-oil (W/O)
- Multiple emulsion
- Microemulsion
Correct answer: Oil-in-water (O/W)
O/W emulsions are miscible with blood (which is aqueous-based), making them suitable for IV use. W/O emulsions are not compatible with blood.
Question 3: A drug with a narrow therapeutic index requires:
- Therapeutic drug monitoring (Correct answer)
- Increased dosing frequency
- Lower protein binding
- Wider dosing intervals
Correct answer: Therapeutic drug monitoring
Narrow therapeutic index drugs have a small margin between therapeutic and toxic doses, necessitating regular therapeutic drug monitoring (TDM) to ensure safety.
Question 4: Which process describes drug movement from blood into tissues?
- Distribution (Correct answer)
- Absorption
- Metabolism
- Elimination
Correct answer: Distribution
Distribution refers to the reversible transfer of a drug from the systemic circulation into tissues and organs throughout the body.
Question 5: What is the significance of a drug's pKa?
- It determines the degree of ionisation at a given pH (Correct answer)
- It indicates the drug's protein binding affinity
- It predicts renal clearance directly
- It measures lipid solubility
Correct answer: It determines the degree of ionisation at a given pH
pKa is the pH at which 50% of the drug is ionised. It helps predict ionisation state at physiological pH, influencing absorption and distribution.
Question 6: Parenteral preparations must be:
- Sterile and pyrogen-free (Correct answer)
- Water-soluble only
- Isotonic only
- Preservative-free only
Correct answer: Sterile and pyrogen-free
Parenteral (injectable) preparations must be sterile and free from pyrogens (bacterial endotoxins) as these can cause fever and serious reactions when injected.
GPhC Pharmaceutical Sciences & Calculations 4
What is the molecular basis of drug tolerance?