Pharmaceutics
Pharmaceutics in NIPER JEE covers dosage-form design, biopharmaceutics, dissolution, bioavailability, stability, rheology, and dispersed systems.
Core rules and concepts
- BCS: Class I high solubility/high permeability; II low solubility/high permeability; III high solubility/low permeability; IV low/low. Solubility is assessed at the highest dose in 250 mL.
- Dissolution: USP Apparatus I (basket) and II (paddle) are common. Similarity factor f2 >50 indicates similar profiles; f2 is not suitable for very rapid dissolution.
- Bioavailability: rate (Cmax, Tmax) and extent (AUC). Bioequivalence compares test and reference products; it does not imply therapeutic equivalence for narrow-therapeutic-index drugs without additional data.
- Stability: Arrhenius equation links degradation rate to temperature; ICH climatic zones guide storage conditions. Shelf life is based on validated stability data.
- Rheology: Newtonian, pseudoplastic (shear-thinning), dilatant, and thixotropic systems. Emulsion HLB guides surfactant selection; flocculated suspensions settle faster but redisperse easily.
Worked example
A 100 mg dose has aqueous solubility 0.05 mg/mL. Volume needed to dissolve the dose = 100/0.05 = 2,000 mL, far above 250 mL, so solubility is low. If permeability is high, the drug is BCS Class II. A formulation strategy is particle-size reduction or lipid solubilization to raise dissolution rate.
Traps that cost marks
- Calling a drug highly soluble without stating the dose and volume.
- Using f2 >50 to claim bioequivalence; f2 compares dissolution profiles only.
- Confusing bioavailability with bioequivalence.
- Ignoring that a flocculated suspension may sediment quickly but is pharmaceutically acceptable because it redisperses.