Viagra metabolism and elimination

Viagra (Sildenafil) is refined basically by the CYP3A4 (main way) and CYP2C9 (secondary way) hepatic microsomal isoenzymes. The basic Sildenafil metabolite is a result from N-desmethylation, and undergoes further metabolism. This main metabolite restricts selectively PDEs like Sildenafil and shows the properties for PDE5 about 50% of the parent medication. This metabolite has 40% plasma levels of those noted for Sildenafil, and thus the metabolite amounts to 20% of Viagra’s pharmacologic effects.

Sildenafil is eliminated as metabolites basically in the feces – about 80% of the received dose and in the urine – about 13% of the dose.

The half life of Sildenafil is about 4 hours, this means that during a period of 4 hours a person may get and maintain an erection. Still the response of a patient decreases after 2 hours after the oral dose. So it is recommended to take Viagra 30 minutes – 2 hours before sexual activity to receive the most pleasant results.

 

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