Thiazides IV: Comparison of dissolution with bioavailability of chlorothiazide tablets.

Based on the initial dissolution rate profiles in water, a slow-dissolving, an intermediate-dissolving, and a fast-dissolving chlorothiazide 250-mg tablet were selected for the bioavailability and bioequivalence study. In addition, two marketed 500-mg chlorothiazide tablets were studied. The three 250-mg tablets were bioequivalent, as were the two 500-mg tablets. Therefore, the dissolution test conditions were modified to associate in vitro dissolution with in vivo performance of the product. Based on these results, it was concluded that a dissolution of 75% in 60 min by paddle method at 75 rpm in pH 7.4 phosphate buffer can be used as a quality assurance test for 250- and 500-mg chlorothiazide tablets.