Pharmacy Drug Delivery Systems 4 — Questions and Answers
Question 1: Ophthalmic solutions must be sterile AND typically buffered to a pH of approximately:
- 4.0–4.5
- 7.4 (Correct answer)
- 9.0–10.0
- 2.0–3.0
Correct answer: 7.4
Ophthalmic formulations are buffered near physiologic tear pH of 7.4 to minimize irritation and maintain drug stability.
Question 2: A drug with a narrow therapeutic index is BEST suited for which delivery strategy?
- Immediate-release tablet taken once daily
- Extended-release formulation to minimize peak-trough fluctuation (Correct answer)
- Bulk powder in a capsule
- Rapidly dissolving sublingual strip
Correct answer: Extended-release formulation to minimize peak-trough fluctuation
Extended-release systems reduce peak-trough fluctuations, keeping plasma concentrations within the narrow therapeutic window.
Question 3: The rate-limiting step in drug release from a reservoir-type transdermal system is:
- Drug dissolution in the reservoir
- The rate-controlling membrane (Correct answer)
- Stratum corneum permeation
- Systemic distribution
Correct answer: The rate-controlling membrane
In reservoir systems, the synthetic rate-controlling membrane (not the skin) governs the drug flux into and through the skin.
Question 4: Cyclodextrins improve drug delivery primarily by:
- Forming covalent bonds with the drug
- Complexing drugs in their hydrophobic cavity to increase solubility (Correct answer)
- Acting as disintegrants
- Lowering the melting point of lipid excipients
Correct answer: Complexing drugs in their hydrophobic cavity to increase solubility
Cyclodextrins form inclusion complexes with hydrophobic drugs in their central cavity, dramatically improving aqueous solubility.
Question 5: Which of the following is a characteristic of a Class II BCS drug?
- High solubility, high permeability
- Low solubility, high permeability (Correct answer)
- High solubility, low permeability
- Low solubility, low permeability
Correct answer: Low solubility, high permeability
BCS Class II drugs are poorly soluble but highly permeable; dissolution rate is the rate-limiting step for absorption.
Question 6: Pegylation of a nanoparticle drug carrier is done PRIMARILY to:
- Increase drug loading capacity
- Evade opsonization and extend circulation time (Correct answer)
- Target specific receptors
- Improve oral absorption
Correct answer: Evade opsonization and extend circulation time
PEG coating creates a steric shield that prevents opsonin adsorption, reducing uptake by the mononuclear phagocyte system.
Question 7: A rectal suppository base melts at body temperature; this type of base is classified as:
- Hydrophilic (water-soluble) base
- Fatty (oleaginous) base such as cocoa butter (Correct answer)
- Emulsifying base
- Absorption base
Correct answer: Fatty (oleaginous) base such as cocoa butter
Fatty bases like cocoa butter and Witepsol melt near 37°C (body temperature) to release drug in the rectal cavity.
Pharmacy Drug Delivery Systems 4
Ophthalmic solutions must be sterile AND typically buffered to a pH of approximately: