Sildenafil inhibits phosphodiesterase type-5 (PDE5) which is responsible for cGMP degradation in the corpus cavernosum. Inhibition of PDE5 increases cGMP levels in the corpus cavernosum which results in smooth muscle relaxation and inflow of blood to the corpus cavernosum.
Aggra 50 Tablet
Adult: 50 mg about 1 hr before sexual intercourse. May adjust dose depending on penile response. Max: 100 mg/dose and not to be taken >once in 24 hr.
Elderly: >65 yr: Lower initial dose at 25 mg.
Pulmonary hypertension: 20 mg 3 times daily
For patients taking drugs which are CYP3A4 inhibitors: initially, 25 mg.
For patients on ritanavir: not >25 mg every 48 hr.
Patients who are stabilised on α-blocker treatment: should use an initial dose of 25 mg. Higher doses should not be taken within 4 hr of an α-blocker.