PSI Pharmaceutical Sciences 2 — Questions and Answers
Question 1: Which parameter best describes the rate of drug elimination from the body?
- Half-life (t½) (Correct answer)
- Volume of distribution
- Bioavailability
- Protein binding
Correct answer: Half-life (t½)
Half-life is the time taken for plasma drug concentration to fall by 50%. It directly reflects the rate of elimination and determines dosing intervals.
Question 2: Michaelis-Menten kinetics apply when enzyme-mediated metabolism is:
- Saturated at high drug concentrations (Correct answer)
- Linear at all concentrations
- Independent of substrate concentration
- Only seen with CYP3A4
Correct answer: Saturated at high drug concentrations
At high concentrations, metabolic enzymes become saturated and elimination shifts from first-order to zero-order kinetics — described by Michaelis-Menten equations.
Question 3: Which solid dosage form release mechanism uses an osmotic pump?
- OROS (Osmotic Release Oral System) (Correct answer)
- Enteric coating
- Matrix tablet
- Immediate release capsule
Correct answer: OROS (Osmotic Release Oral System)
OROS uses osmotic pressure to drive water into a core compartment, pushing drug through a laser-drilled orifice at a controlled, constant rate.
Question 4: Which property does the partition coefficient (log P) measure?
- Lipophilicity of a drug (Correct answer)
- Solubility in water
- Degree of ionisation
- Molecular weight
Correct answer: Lipophilicity of a drug
Log P is the ratio of drug concentration in octanol vs water, indicating how lipophilic a molecule is. High log P means good membrane permeability but poor aqueous solubility.
Question 5: Hygroscopic drug substances require which type of packaging?
- Moisture-barrier packaging (Correct answer)
- Amber glass bottles
- Strip foil only
- PET containers
Correct answer: Moisture-barrier packaging
Hygroscopic substances absorb moisture from the environment, leading to degradation. Moisture-barrier packaging (e.g., blister with aluminium foil) protects product stability.
Question 6: What does the term 'polymorphism' refer to in pharmaceutical sciences?
- Different crystal structures of the same compound (Correct answer)
- Different salts of the same drug
- Variation in patient metabolism
- Multiple dosage forms of one drug
Correct answer: Different crystal structures of the same compound
Polymorphism describes the ability of a solid material to exist in more than one crystal form. Different polymorphs can have different solubility and bioavailability.
PSI Pharmaceutical Sciences 2
Which parameter best describes the rate of drug elimination from the body?