Stability Indicating Assay Method for Simultaneous Estimation of Tadalafil and Dapoxetine Hydrochloride by RP-HPLC in Bulk

A new simple validated RP-HPLC stability indicating assay method was developed for simultaneous estimation of dapoxetine hydrochloride and tadalafil in bulk drug. C₁₈ Phenomenex Hyper Clone™ BDS column (250 × 4.5 mm, 5 μm), was used along with mobile phase composition of acetonitrile: potassium phosphate buffer 10 mM (55:45 at pH 3.2 ± 0.1). Flow rate for study was 1 mL/min whereas response curve was measured with photodiode array detector at 298 nm. Tadalafil retention time was 3.9 min and that of dapoxetine hydrochloride was 4.9 min. Linearity of both drugs were found between the range of 6-16 μg/mL. The stability indicating ability of the method was establish by analysing drug sample by acid and alkaline hydrolysis, photolytic, oxidative and thermal conditions. The developed method is expeditious, precise and simple and can be implemented for quality control studies.