Pharmacy Drug Delivery Systems 3 — Questions and Answers
Question 1: Enteric coating on a tablet is designed to dissolve at:
- pH 1–2 (stomach)
- pH above 5.5–6 (small intestine) (Correct answer)
- pH 7.4 (blood)
- pH 8–9 (colon)
Correct answer: pH above 5.5–6 (small intestine)
Enteric coatings use polymers like CAP or Eudragit L that remain intact in acidic gastric pH but dissolve at the higher pH of the small intestine.
Question 2: Which inhalation device requires the patient to generate sufficient inspiratory flow to disperse the drug?
- Pressurized metered-dose inhaler (pMDI)
- Nebulizer
- Dry powder inhaler (DPI) (Correct answer)
- Soft mist inhaler
Correct answer: Dry powder inhaler (DPI)
DPIs are breath-actuated and rely on the patient's inspiratory effort to deagglomerate and aerosolize the dry powder.
Question 3: In parenteral formulations, isotonicity is adjusted to match blood osmolarity of approximately:
- 150 mOsm/kg
- 308 mOsm/kg (Correct answer)
- 500 mOsm/kg
- 100 mOsm/kg
Correct answer: 308 mOsm/kg
Blood osmolarity is approximately 285–310 mOsm/kg; 0.9% NaCl (normal saline) is isotonic at ~308 mOsm/kg.
Question 4: A prodrug is a pharmacologically inactive compound that:
- Is stored in fat tissue until released
- Is converted in vivo to an active drug (Correct answer)
- Binds irreversibly to plasma proteins
- Forms a chelate with metal ions
Correct answer: Is converted in vivo to an active drug
Prodrugs are designed to be biotransformed in the body into the pharmacologically active parent drug.
Question 5: Which property of a drug MOST favors absorption via the buccal or sublingual route?
- High molecular weight (>1000 Da)
- High lipophilicity and low ionization at oral pH (Correct answer)
- Poor membrane permeability
- Complete first-pass extraction
Correct answer: High lipophilicity and low ionization at oral pH
Lipophilic, unionized drugs readily partition through the thin, vascular oral mucosa without hepatic first-pass metabolism.
Question 6: The term 'depot injection' refers to a formulation that:
- Must be injected into a vein
- Creates a drug reservoir at the injection site for prolonged release (Correct answer)
- Dissolves immediately upon injection
- Requires reconstitution before every dose
Correct answer: Creates a drug reservoir at the injection site for prolonged release
Depot injections (e.g., microsphere suspensions, oil solutions) release drug slowly from the injection site over days to months.
Question 7: Which polymer is used in PLGA microspheres to control drug release by biodegradation?
- Poly(lactic-co-glycolic acid) (Correct answer)
- Polyethylene glycol (PEG)
- Hydroxypropyl methylcellulose (HPMC)
- Carbomer
Correct answer: Poly(lactic-co-glycolic acid)
PLGA degrades by hydrolysis of ester bonds in vivo, providing controlled drug release over weeks to months.
Pharmacy Drug Delivery Systems 3
Enteric coating on a tablet is designed to dissolve at: