N-Desmethyl Sildenafil (Desmethylsildenafil) is a major metabolite of Sildenafil. Sildenafil is a potent phosphodiesterase type 5 (PDE5) inhibitor[2].In Vitro: N-Desmethyl Sildenafil increases the amplitude of electroretinogram (ERG) recorded from the dark-adapted isolated rat retina, most probably through the enhancement of the photoreceptor cell response.
The formation of N-Desmethyl Sildenafil is examined using CYP3A supersomes co-expressing human P450 oxidoreductase and cytochrome b5. N-Desmethyl Sildenafil is catalyzed by CYP3A4, CYP3A5, and to a lesser extent by CYP3A7[2].