Pharmaceutics and Pharmaceutical Technology
Pharmaceutics and Pharmaceutical Technology tests how physicochemical properties, formulation, and manufacturing determine drug release, absorption, and therapeutic performance. Expect questions that connect BCS class, dissolution, bioavailability, and process controls rather than isolated definitions.
Core rules
- The Biopharmaceutics Classification System uses aqueous solubility and intestinal permeability: class I high/high, II low solubility/high permeability, III high solubility/low permeability, IV low/low.
- For BCS II, dissolution rate often limits absorption; Noyes–Whitney predicts rate rises with surface area and solubility and falls with particle size. Formulation tactics include micronization, amorphous solid dispersions, lipid systems, and cyclodextrins, but supersaturation must be stabilized to avoid precipitation.
- Modified-release profiles: zero-order is constant, first-order is concentration-dependent, Higuchi is matrix diffusion, and Korsmeyer–Peppas gives a mechanistic exponent.
- Bioavailability is rate and extent of absorption; bioequivalence compares AUC and Cmax within confidence limits, not dissolution alone.
Worked example
A BCS II weak base has high permeability but near-zero fasting solubility. A conventional tablet gives erratic AUC. Reasoning: permeability is not limiting; dissolution and solubility are. An amorphous solid dispersion may generate supersaturation, but add precipitation inhibitors and test in biorelevant media. Do not simply micronize if wettability remains poor. Confirm with dissolution and pharmacokinetic data; an in vitro–in vivo correlation is possible only when in vitro release is the rate-limiting step.
Traps
Equating bioavailability with absorbed fraction; assuming all modified-release forms are zero-order; ignoring food, pH, and salt effects; treating a dissolution similarity factor as proof of bioequivalence.