Stability-indicating assay for chlorthalidone formulation: evaluation of the USP analysis and a high-performance liquid chromatographic analysis.

An investigation of the USP assay of chlorthalidone tablets showed that variable degradation of chlorthalidone occurred during assay preparation. The degradation products were isolated and identified. A stability-indicating high-performance liquid chromatographic (HPLC) assay which separates the degradation products from chlorthalidone was developed and used to examine the present USP preparation. The HPLC assay is suggested as an alternate.