for the treatment of pulmonary arterial hypertension (WHO Group I) to improve exercise ability

Sildenafil citrate is a selective inhibitor of cGMP specific phosphodiesterase type-5 (PDE5) in smooth muscle, where PDE5 is responsible for degradation of cGMP. Sildenafil citrate increases cGMP within vascular smooth muscle cells resulting in relaxation and vasodilation. In patients with pulmonary hypertension, this leads to vasodilation of the pulmonary vascular bed and, to a lesser degree, vasodilation in the systemic circulation

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.

Pulmonary hypertension: 20 mg ORALLY 3 times daily; give doses approximately 4 to 6 hr apart, with or without food. In the clinical trial no greater efficacy was achieved with the use of higher doses. Treatment with doses higher than 20 mg t.i.d. is not recommended.