Pharmaceutics, Dosage Forms, and Pharmaceutical Technology
What the domain tests
This domain tests dosage-form design and manufacturing principles: dissolution, bioavailability, excipient function, stability, modified-release behavior, and quality attributes. Questions often present a formulation problem-poor solubility, poor flow, or inconsistent release-and ask for the most appropriate technological solution.
Core rules and concepts
- The Biopharmaceutics Classification System (BCS) groups drugs by solubility and permeability. BCS class II drugs (low solubility, high permeability) are often dissolution-rate limited; class III (high solubility, low permeability) are permeability limited.
- For immediate-release oral solids, disintegration and dissolution must precede absorption. Disintegrants, binders, lubricants, and surfactants must be balanced; excessive lubricant can slow dissolution.
- Modified-release forms use matrices, coatings, or osmotic systems. Crushing or splitting can cause dose dumping and toxicity.
- Stability depends on moisture, temperature, light, and pH. Hydrolysis, oxidation, and photolysis are common degradation routes; antioxidants, desiccants, and protective packaging mitigate them.
- Bioequivalence compares rate and extent of absorption, usually via AUC and Cmax with confidence intervals; it is not identical to clinical interchangeability for every product.
Worked example
A BCS class II weak acid tablet shows low and variable bioavailability. The drug is crystalline and poorly wettable. A rational approach is to increase dissolution rate by micronization or a solid dispersion, or to use a salt form if chemically feasible. The reasoning: low solubility limits dissolution, and dissolution limits absorption. Simply adding more lubricant or compressing harder would slow dissolution further. The formulation scientist must also confirm that the selected approach does not destabilize the drug or change food effects.
Traps that cost marks
Do not assume a bioequivalent generic is identical in every excipient. Do not recommend crushing a modified-release tablet for dysphagia without checking the formulation. Do not confuse content uniformity with dissolution. Do not ignore excipient incompatibilities in stability.
Key points
- BCS links solubility and permeability to absorption limits.
- Dissolution is critical for many oral solids.
- Modified-release forms may dose-dump if crushed.
- Stability is formulation- and environment-dependent.
- Bioequivalence uses AUC and Cmax, not just in vitro release.