Bioequivalence study of sildenafil citrate tablets in healthy human volunteers.

Newly developed sildenafil citrate (SC), a selective inhibitor of cyclic guanosine monophosphate (c-GMP) specific phosphodiesterase type 5 (PDE 5) in the corpus cavernosum is used for the oral treatment of erectile dysfunction. A convenient, sensitive and simple method for the determination of sildenafil in human plasma is presented. The analytical technique was based on reversed-phase high-performance liquid chromatography coupled with UV detector set at 295 nm. Rofecoxib was used as internal standard (I.S). Liquid-liquid extraction using diethyl ether was performed to recover sildenafil and rofecoxib. The retention time of I.S and sildenafil were 5.5 minutes and 7.2 minutes respectively. The method was validated over a linear range of 10 to 1000 ng/ml from plasma. Separate stability study showed that sildenafil is stable under conditions of analysis. The extraction efficiency from plasma varied from 79.69% to 81.13 %. The minimum quantifiable concentration was set at 10 ng/ml. (%o CV<12.5%). The method was used for Bioequivalence Study of Two Brands of Sildenafil citrate 50 mg tablets in healthy human volunteers. All pharmacokinetic parameter were calculated along with statistical evaluation.