It is good for the occasional user but must be taken on an empty stomach. If too much is used, the chance of side effects is increased. If you become pregnant while taking sildenafil, call your doctor. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco. Use only the brand of this medicine that your doctor prescribed. It lasts 4 to 5 hours, or longer if you have mild to moderate ED.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.  · Teva sildenafil is a generic version of Viagra used to treat erectile dysfunction (ED) and some heart conditions. Learn about Teva sildenafil and how to use it. mg; It also comes as an.  · Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra Drug classes: Agents for pulmonary hypertension, Impotence agents. Medically reviewed by Kaci Durbin, MD. Last updated on Uses; Warnings; Before taking; Dosage; Side effects; Interactions; FAQ; What is sildenafil?