MPharm Master of Pharmacy Master of Pharmacy: Pharmaceutical Technology and Drug Delivery Systems 2 — Questions and Answers
Question 1: Which transdermal drug delivery parameter measures the maximum rate of drug flux across a unit area of skin?
- Bioavailability fraction (F)
- Steady-state flux (Jss) (Correct answer)
- Volume of distribution (Vd)
- First-pass extraction ratio
Correct answer: Steady-state flux (Jss)
Steady-state flux (Jss) is the maximum rate of drug permeation per unit area of skin under a constant concentration gradient, determined by Fick's first law of diffusion.
Question 2: In spray drying of pharmaceutical powders, what is the primary variable that controls final particle size?
- Inlet air temperature
- Feed solution concentration
- Atomization pressure or nozzle tip speed (Correct answer)
- Drying chamber volume
Correct answer: Atomization pressure or nozzle tip speed
Atomization conditions (pressure for two-fluid nozzles or rotational speed for rotary atomizers) determine initial droplet size, which directly controls the final dry particle size.
Question 3: Which release profile is described as 'zero-order' drug release?
- Release rate decreases exponentially with time
- Release rate is constant and independent of drug concentration (Correct answer)
- Release rate is proportional to the square root of time (Higuchi model)
- Release rate increases initially then plateaus
Correct answer: Release rate is constant and independent of drug concentration
Zero-order release means a constant amount of drug is released per unit time regardless of remaining drug concentration, which is ideal for maintaining steady plasma levels.
Question 4: What is the purpose of the 'pore former' component added to ethylcellulose membrane coatings on pellets?
- To increase coating adhesion to the pellet core
- To dissolve and create micropores that control drug permeation (Correct answer)
- To reduce the burst release effect
- To improve color uniformity of the coating
Correct answer: To dissolve and create micropores that control drug permeation
Water-soluble pore formers (e.g., HPMC, PVP) dissolve upon contact with aqueous media, creating channels in the otherwise impermeable ethylcellulose membrane through which drug can diffuse.
Question 5: In the preparation of microspheres by solvent evaporation, which method is used when the drug is dissolved in the polymer solution?
- Coacervation method
- Spray congealing
- Oil-in-oil (O/O) emulsion evaporation
- Single emulsion (O/W) solvent evaporation (Correct answer)
Correct answer: Single emulsion (O/W) solvent evaporation
For hydrophobic drugs soluble in an organic solvent, the drug-polymer solution is emulsified in an aqueous continuous phase (O/W), and solvent is evaporated to harden the polymer microspheres.
Question 6: Which lyophilization (freeze-drying) stage involves removal of bound or unfrozen water under reduced pressure and elevated temperature?
- Primary drying (sublimation)
- Pre-freezing stage
- Secondary drying (desorption) (Correct answer)
- Annealing phase
Correct answer: Secondary drying (desorption)
Secondary drying removes residual bound water (unfrozen water molecules attached to the dried product) by raising shelf temperature above 0°C under vacuum, reducing moisture content to 0.5–3%.
Question 7: What is the critical micelle concentration (CMC) in the context of surfactant-based drug formulations?
- The concentration at which a surfactant begins to denature proteins
- The minimum concentration above which surfactant molecules form aggregated micellar structures (Correct answer)
- The maximum solubility of a surfactant in organic solvents
- The concentration at which emulsion phase inversion occurs
Correct answer: The minimum concentration above which surfactant molecules form aggregated micellar structures
Above the CMC, additional surfactant molecules self-assemble into micelles rather than remaining as monomers; drugs can be solubilized within micelle cores above this concentration.
