Pharmacokinetics: Sildenafil is administered orally. The drug is rapidly absorbed after oral administration, with absolute bioavailability of about 40%. Its pharmacokinetics are dose-proportional over the recommended dose range. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. When sildenafil is taken with a [...]

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Mechanism of Action: Sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cGMP. Cyclic guanosine [...]

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What It Does: Sildenafil (Viagra) is a phosphodiesterase inhibitor. It is administered orally for the treatment of male erectile dysfunction (ED) and pulmonary arterial hypertension (PAH).
Brief History of Viagra: Sildenafil was originally developed as an antianginal agent but was found to be more effective in treating ED and subsequently PAH. In regards to ED, sildenafil [...]

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