Substance: Sildenafil
Country: India
Form: 100mg/sachet
Amount: 7 Sachets
Recommended Dosage: 100mg 30 minutes prior to sexual activity
Description:
Sildenafil prevents degradation of cGMP by 5-phosphodiesterase (PDE5) in the corpus cavernosum. Nitric Oxide in the corpus cavernosum of the penis binds to guanylate cyclase receptors which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of blood vessels. This has the effect of increased inflow of blood into the spongy tissue of the penis, causing an erection.
Sildenafil is a potent and selective inhibitor of PDE5, which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of Sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, Sildenafil should not cause an erection. Sildenafil is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4(major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further. This metabolite also has an affinity for the PDE receptors, about 40% of that of Sildenafil. Thus, the metabolite is responsible for about 20% of Sildenafil's action. Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose). If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third.
