Biowaiver assessment of some commercially available brands of valsartan tablets using in vitro methods

Background: Generic medicines must be therapeutic equivalents with the innovator brand before substitution is appropriate.

Objective: This study was carried out to evaluate the in vitro equivalence of valsartan (a BCS Class III drug) tablets under Biowaiver conditions.

Methods: Physicochemical parameters were assessed in accordance with BP and USP specifications. Therapeutic equivalence of the innovator and commonest generic brands were investigated using in vitro methods.

Results: The tested valsartan brands investigated complied with Compendia specifications for tablets. Valsartan tablets were not very rapidly dissolving as per WHO Biowaiver testing specifications. Both test and reference products were poorly soluble in acidic medium (pH 1.2), while 85% of the drug was released at 15 minutes in pH 6.8. Dissolution profiles of the test and innovator brands were similar at pH 1.2 and 6.8 (f2: 65 and 69 respectively), and dissimilar at pH 4.5 (f2: 30). The generic valsartan tablets evaluated in this study showed pharmaceutical equivalence with the innovator brand. The test and reference products were not however very rapidly dissolving as required for BCS Class III drugs.

Conclusion: The valsartan tablet brands tested did not meet WHO BCS-based biowaiver conditions. In vivo bioequivalence studies are recommended to ascertain therapeutic equivalence and interchangeability.