Pharmaceutics and Pharmaceutical Technology
Core concepts
Master dosage-form design: solutions, suspensions, emulsions, tablets, capsules, suppositories, semisolids, and sterile products. Know the excipient roles (diluent, binder, disintegrant, lubricant, glidant, coating, preservative, antioxidant, buffer, suspending agent, emulsifier). Understand rheology (Newtonian vs non-Newtonian, thixotropy), particle-size reduction and its effect on dissolution, and the difference between dissolution rate and solubility.
Biopharmaceutics
Learn the BCS classes (high/low solubility × high/low permeability) and what each implies for formulation strategy. Know that the rate-limiting step to absorption may be dissolution (Class II) or permeability (Class III). Understand bioavailability (F), bioequivalence criteria, and the meaning of AUC, Cmax, and Tmax. Sterile products require understanding of sterilization methods (moist heat, dry heat, filtration, radiation) and which products tolerate which method; preservative efficacy and pyrogen control matter for multidose and parenteral products.
Traps in questions
- Equating dissolution with solubility; a drug can be very soluble but dissolve slowly if particle size is large.
- Choosing terminal dry-heat sterilization for a heat-labile solution (filtration is correct).
- Forgetting that a lubricant (e.g., magnesium stearate) can retard dissolution if over-blended.
- Confusing stability (chemical integrity) with shelf-life specifications.
Worked example (rule of thumb)
A Class II drug (low solubility, high permeability) is dissolution-rate limited: reduce particle size, use a salt or amorphous form, or add a solubilizer. A Class III drug (high solubility, low permeability) is permeability-limited: formulation changes to particle size will not help much; permeation enhancers or alternative routes are the lever.