File Entry: Synthesis of Sildenafil Citrate Validated HPLC Method and Its Pharmaceutical Dosage Forms

The present study describes analytical method of 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H–pyrazolo[4,3-d]pyrimidin-5-yl)-4- ethoxyphenyl]sulphonyl]-4methypiperazine citrate (sildenafil Citrate). The following specification particularly describes and ascertains the nature of this invention, and the manner in which it is to be performed. Sildenafil is an oral drug used primarily to treat male sexual function problems (impotence or erectile dysfunction) since becoming available in 1998. It is a potent and selective inhibitor of cGMP specific Phosphodiesterase Type 5 (PDE5) in the corpus cavernosum, where PDE5 is responsible for degradation of cGMP. Sildenafil has a peripheral site of action on erections. This substance has no direct relaxant effect on isolated human corpus cavernosum but potently enhances the relaxant effect of nitric oxide on this tissue. However, there is no analytical method for determination of this active compound in pharmaceutical preparations in the current European and US Pharmacopoeia. The aim of this study was to develop and validate HPLC method for sildenafil analysis in pharmaceutical dosage forms.

Keywords: Chlorosulphonyl Intermediate; N-Methylpiperazine; Sildenafil; IR; HPLC Validation

Abbreviations: PDE5: Phosphodiesterase Type 5; GMP: Guanosine Monophosphate; LOD: Limit of Detection; LOQ: Limit of Quantification; cGMP: Cyclicguanosine Monophosphate