Erectile dysfunction

In patients with erectile dysfunction, sildenafil citrate enhances the effect of nitric oxide (NO) by inhibiting PDE5 in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil citrate causes increased levels of cGMP resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum.

Onset of action: ~60 minutes; Duration: 2-4 hours; absolute bioavailability: about 40%; Time to peak: 30-120 minutes; delayed by 60 minutes with a high-fat meal; Protein binding: 96%; Metabolism: Hepatic: CYP3A4 (major) and CYP2C9 (minor); Active metabolite: N-desmethyl metabolite, accounts for 20% of sildenafil's pharmacologic effects; Excretion: Feces (80%); urine (13%)

Hypersensitivity to sildenafil or any component of the formulation; concurrent use (regularly/intermittently) of organic nitrates in any form (eg, nitroglycerin, isosorbide dinitrate)

B

Excretion in breast milk unknown/use caution

common: flushing, rash, dizziness, headache, nasal congestion. Adverse effects such as flushing, diarrhea, myalgia, and visual disturbances may be increased with doses >100 mg/24 hours.

Erectile dysfunction: 25 to 100 mg (50 mg usual dose) ORALLY 1 hr (range 0.5 to 4 h) prior to sexual activity; MAX frequency of administration once daily