Pharmaceutics and Pharmaceutical Dosage Forms
Core concepts
Understand formulation science across solid, liquid, semisolid, and parenteral dosage forms. Key ideas: particle size and surface area effects on dissolution, polymorphism and its effect on solubility and stability, excipient roles (diluents, binders, disintegrants, lubricants, glidants, coatings), and manufacturing methods (direct compression, wet granulation, fluid-bed drying). For liquids, know solubility enhancement (cosolvents, surfactants, pH adjustment), preservation, and stability. For parenterals, know isotonicity, sterility assurance, pyrogen control, and the difference between sterilization methods (moist heat, dry heat, filtration, radiation). Understand bioavailability differences among dosage forms and the concept of the rate-limiting step in drug release.
Question traps
Questions often test which excipient performs which function - a lubricant (magnesium stearate) is not a glidant, and a binder is not a disintegrant. Another trap is assuming a more stable polymorph is also more soluble; usually the more stable form is less soluble. Watch for items on sterilization: moist heat is for aqueous solutions, dry heat for glassware and nonaqueous materials, filtration for heat-labile solutions.
Worked rule of thumb
If a candidate asks why a tablet dissolves slowly, check the Biopharmaceutics Classification System: a low-solubility, high-permeability (Class II) drug is dissolution-rate limited, so reducing particle size or using a solid dispersion helps. A high-solubility, low-permeability (Class III) drug is permeability limited, so particle size reduction will not help much.
Study approach
Organize by dosage form and list: purpose, critical excipients, manufacturing step, and quality test.