Pharmaceutical equivalence is an important issue in the regulatory approval of generic and similar drug products, particularly for those that will not be tested for bioequivalence. However, there is no scientific approach that provides us an objective measure of quality and similarity of the results obtained for testing (generic or similar) and branding drug products simultaneously. This paper describes a new multivariate similarity factor for the assessment of in vitro therapeutic equivalence

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... etween two medicines by using pharmaceutical equivalence study. We performed pharmaceutical equivalence studies for acyclovir cream, metronidazole injection, meropenem for injection and atropine sulfate injection. All tests and assays results were standardized using an appropriate desirability function. Multivariate similarity factors for pharmaceutical studies were calculated based on individual acceptance factors and similarity deviations for brand, generic, and similar drugs. We found a perfect correlation among multivariate similarity factor and regulatory requirements. The multivariate similarity factor is a useful tool for in vitro therapeutic equivalence assessment, and may be used for regulatory approval of generic and similar drugs.