In vivo studies: No significant interactions were shown with tolbutamide mg or warfarin 40 mg , both of which are metabolized by CYP2C9. Do not start these medications while taking sildenafil without discussing it with your healthcare provider. The patient addressed both questions at the final visit for the last 4 weeks of the study. Use protective measures and ask your doctor if you have any questions about this. Maximum observed plasma concentrations are reached within 30 to minutes median 60 minutes of oral dosing in the fasted state.Viagra. Compare prices and print coupons for Sildenafil (Generic Revatio and Viagra) and other drugs at CVS, Walgreens, and other pharmacies. Prices start at $ Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision.