If you experience a prolonged or painful erection for 4 hours or more, contact your doctor immediately. Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors such as tolbutamide, warfarin , CYP2D6 inhibitors such as selective serotonin reuptake inhibitors, tricyclic antidepressants , thiazide and related diuretics, ACE inhibitors, and calcium channel blockers. Dosing The dose of this medicine will be different for different patients. Sildenafil for pulmonary hypertension can also be known by the brand names Revatio and Grandipam. Also collected as part of the IIEF was information about other aspects of sexual function, including information on erectile function, orgasm, desire, satisfaction with intercourse, and overall sexual satisfaction.Sildenafil citrate is a white to off-white crystalline powder with a solubility of mg/mL in water and a molecular weight of VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and mg of sildenafil for oral administration. In studies of Viagra, some side effects were more common with a mg dose than a mg dose. These include headache, indigestion, vision changes, and stuffy nose. But other side effects. Sildenafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual stimulation, sildenafil works by increasing blood flow to the penis.