Adults

The recommended dose is 50 mg taken approximately 1 hour before sexual activity. The dose may be increased to 100 mg or decreased to 25 mg based on efficacy and tolerability. Maximum recommended dosing frequency is once per day.

Elderly

No dosage adjustment is required in elderly patients. However, a starting dose of 25 mg may be considered due to potential age-related decrease in clearance.

Renal_impairment

For patients with severe renal impairment (creatinine clearance <30 mL/min), a starting dose of 25 mg should be considered. No dosage adjustment is required for mild to moderate renal impairment.

Onset

30-60 minutes.

Excretion

Excreted predominantly as metabolites in feces (approximately 80% of administered oral dose) and to a lesser extent in urine (approximately 13% of administered oral dose).

Half life

Approximately 3-5 hours.

Absorption

Rapidly absorbed after oral administration, with peak plasma concentrations occurring within 30-120 minutes. Absolute bioavailability is approximately 41%.

Metabolism

Primarily metabolized by hepatic microsomal isoenzymes CYP3A4 (major route) and CYP2C9 (minor route). The major circulating metabolite, N-desmethyl sildenafil, has about 50% of the activity of sildenafil.

Nitrates

Potentiation of hypotensive effects, leading to severe and potentially fatal hypotension. Concomitant use is absolutely contraindicated.

Riociguat

Concomitant use is contraindicated due to increased risk of hypotension.

Alpha-blockers

May lead to symptomatic hypotension in some patients, especially within 4 hours of sildenafil administration.

CYP3A4 inhibitors (e.g., Ritonavir, Ketoconazole, Erythromycin)

Increase sildenafil plasma concentrations, requiring a reduced starting dose of sildenafil.