Answered By: Dr. If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. D Dec 12, Is the Teva generic the same of brand Viagra? Sildenafil usually should not be taken more than once every 24 hours. If you have an erection that lasts more than 4 hours, get medical help right away. Sildenafil Viagra is used to treat erectile dysfunction impotence; inability to get or keep an erection in men. Answer: It depends on the person taking it and what their sexual habits are.The Savings Offer and Program expire on 12/31/ For further information, call , visit test1.ru, or write: Viatris Inc., P.O. Box , Mission, KS . 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 .  · Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat .