**2.15 Criteria for bioequivalence**

A 90% confidence interval is considered to establish bioequivalence for AUC, Tmax, and Cmax which should fall within the range of 80–125%. A 5% level of significance is taken for rejection of one sided t-test with the null hypothesis of bioequivalence. In bioavailability studies, closer limits are considered for drug that have a narrow therapeutic index, serious dose-related toxicity, steep dose, effect curve, and nonlinear pharmacokinetics within the therapeutic dose range. A wider acceptance range may be admissible if it is based on sound clinical justification. In case of suprabioavailability, a reformulation of the drug product is required and again bioequivalence study has to be carried out. Application of new formulation is required to support the clinical trial data especially for dosage recommendations. Such formulations are usually not being accepted as therapeutically equivalent to the existing reference drug.
