Bioequivalence of generic and branded amoxicillin capsules in healthy human volunteers

The Medical Council of India urges doctors to prescribe generic drugs as far as possible. The Indian Medical Association had responded earlier saying that it requires guarantees on the quality of generic forms of drugs. Although no published scientific reports are available on the issue of therapeutic inequivalence, unconfirmed clinician accounts and newspaper reports of therapeutic inequivalence exist.

This study was planned to ascertain whether bioequivalence of branded and generic amoxicillin capsule is comparable.

An open-label, randomized, single-dose, two-treatment, two-sequence, two-period crossover oral bioequivalence study was conducted in 12 healthy, adult human subjects under fasting condition.

Serum samples, collected at 8 time points, were analyzed by a validated ultraviolet spectrophotometer method. Pharmacokinetic (PK) parameters such as area under the curve (AUC)_0-t, AUC_0-∞, C_max, and T_max were determined along with time above minimum inhibitory concentration (MIC).

The log-transformed PK parameters (C_max, AUC_0-t, AUC_0-∞) were analyzed using a Two One-Sided Test ANOVA in SAS for each parameter. T_max and MIC were analyzed by Wilcoxon rank-sum test in GraphPad Prism.

Geometric mean ratio of C_max fell within bioequivalence criteria. The upper and lower confidence limits of both AUC_0-t and AUC_0-∞ geometric mean ratio fell below bioequivalence criteria. Time above MIC of generic preparation was significantly lower than that of branded version.

The generic capsule was not bioequivalent to the branded amoxicillin capsule.