Development and Validation of Stability-Indicating HPLC Method for Simultaneous Quantification of Vardenafil and Dapoxetine in Bulk and in Combined Dosage Form

An understanding of drug product degradation issues is needed to advise stable formulation and provide a reasonable shelf-life evaluation for all drug products. For this purpose, we have developed and validated a novel HPLC method for assessing the stability of vardenafil and dapoxetine in a combined pharmaceutical dosage form. The chromatographic separation was accomplished on a ProntoSIL C18 KROMA PLUS column (250x4.6 mm, 5 mu m). The column was run under isocratic conditions with a 2.0 mL/min flow rate. The mobile phase was made up of methanol and 20 mM potassium dihydrogen phosphate at 45 : 55 (v/v), which was adjusted to pH 3.0 with phosphoric acid; these two drugs were eluted at retention times of 5.33 and 9.91 min for vardenafil and dapoxetine, respectively. The proposed method shows a linearity of 1-50 ug/ml with a regression of 0.9999 for both drugs. The method was validated for accuracy, precision, linearity, specificity, and sensitivity. The developed HPLC method has been successfully implemented to analyse dapoxetine and vardenafil in tablets. Furthermore, the stress degradation experiments were conducted on the bulk powder of vardenafil and dapoxetine following the International Council for Harmonization (ICH) recommendations.