MPharm Master of Pharmacy Master of Pharmacy: Pharmaceutical Technology and Drug Delivery Systems 1 — Questions and Answers
Question 1: Which parameter in the Noyes-Whitney equation directly describes the rate of drug dissolution?
- Partition coefficient
- Surface area of the dissolving solid (Correct answer)
- Henderson-Hasselbalch ratio
- Renal clearance
Correct answer: Surface area of the dissolving solid
The Noyes-Whitney equation states that dissolution rate is directly proportional to the surface area of the solid, so smaller particle size (larger surface area) increases dissolution.
Question 2: In liposomal drug delivery, what is the term for liposomes engineered to avoid rapid clearance by the mononuclear phagocyte system?
- Cationic liposomes
- Stealth liposomes (Correct answer)
- Multilamellar vesicles
- Niosomes
Correct answer: Stealth liposomes
Stealth liposomes are coated with polyethylene glycol (PEG), which creates a hydrophilic shield that prevents opsonization and prolongs circulation time.
Question 3: Which type of controlled-release mechanism relies on osmotic pressure to drive drug release at a constant rate?
- Matrix diffusion system
- Reservoir membrane system
- Elementary osmotic pump (OROS) (Correct answer)
- Ion-exchange resin complex
Correct answer: Elementary osmotic pump (OROS)
The elementary osmotic pump uses a semipermeable membrane and an orifice; water enters by osmosis, creating pressure that pushes drug solution out at a controlled zero-order rate.
Question 4: What is the primary purpose of using a plasticizer in film-coating of tablets?
- To increase the melting point of the polymer
- To reduce film permeability to moisture
- To improve flexibility and reduce brittleness of the coating film (Correct answer)
- To enhance drug solubility in the core
Correct answer: To improve flexibility and reduce brittleness of the coating film
Plasticizers like polyethylene glycol or triethyl citrate are incorporated into polymer coatings to reduce glass transition temperature, making the film more flexible and preventing cracking.
Question 5: Which emulsification theory explains stabilization of emulsions by the formation of a monomolecular film at the oil-water interface?
- Oriented wedge theory
- Interfacial film theory (Correct answer)
- Repulsion theory
- Phase volume ratio theory
Correct answer: Interfacial film theory
The interfacial film theory states that emulsifying agents form a condensed, coherent monomolecular film at the interface that mechanically prevents coalescence of droplets.
Question 6: In solid lipid nanoparticles (SLNs), which characteristic distinguishes them from conventional lipid emulsions?
- They contain liquid lipids instead of solid lipids
- The lipid core is solid at body temperature (Correct answer)
- They are larger than 10 micrometers
- They cannot incorporate lipophilic drugs
Correct answer: The lipid core is solid at body temperature
SLNs use lipids that remain solid at physiological temperature (37°C), providing a solid matrix that offers controlled drug release and enhanced physical stability compared to liquid nanoemulsions.
Question 7: What does a drug's HLB (Hydrophilic-Lipophilic Balance) value of 4 indicate about its primary use?
- Suitable as a solubilizing agent for injectable formulations
- Appropriate as a wetting agent
- Suitable as a water-in-oil (W/O) emulsifier (Correct answer)
- Appropriate as an oil-in-water (O/W) emulsifier
Correct answer: Suitable as a water-in-oil (W/O) emulsifier
A low HLB value (3–6) indicates a predominantly lipophilic surfactant, which preferentially stabilizes water-in-oil emulsions where water droplets are dispersed in an oil phase.
