Adults

For Erectile Dysfunction: Initial dose of 50 mg taken orally approximately 1 hour before sexual activity. Based on efficacy and tolerability, the dose may be increased to 100 mg or decreased to 25 mg. Maximum recommended dosing frequency is once per day.

Elderly

No dosage adjustment is required for elderly patients (≥65 years) unless there is severe renal or hepatic impairment.

Renal_impairment

For severe renal impairment (creatinine clearance <30 mL/min), a starting dose of 25 mg should be considered. For mild to moderate impairment, no adjustment is needed.

Onset

Onset of action typically occurs within 30-60 minutes after administration.

Excretion

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

Half life

The mean terminal half-life of Sildenafil is approximately 3-5 hours. The active metabolite, N-desmethyl sildenafil, has a terminal half-life of approximately 4 hours.

Absorption

Rapidly absorbed. Peak plasma concentrations (Tmax) are reached within 30-120 minutes (median 60 min) after oral dosing in the fasted state. Absolute bioavailability is approximately 41%.

Metabolism

Primarily metabolized by hepatic microsomal isoenzymes CYP3A4 (major route) and CYP2C9 (minor route).

Nitrates

Contraindicated due to the risk of severe and potentially fatal hypotension.

Riociguat

Contraindicated, concomitant use may cause symptomatic hypotension.

Alpha-blockers

May lead to symptomatic hypotension. Use with caution, initiate at lowest dose of sildenafil.

CYP3A4 Inhibitors (e.g., ketoconazole, ritonavir, erythromycin)

May increase sildenafil plasma concentrations, consider a lower starting dose of sildenafil.