Key facts It usually takes 30 to 60 minutes for sildenafil to work for erectile dysfunction. You can take it up to 4 hours before you want to have sex. The effects may be increased because of slower removal of the medicine from the body. To use the oral liquid: Shake the bottle well for at least 10 seconds before each use. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. It continues to work for up to 4 hours, although its action is usually less after 2 hours. Age greater than 50 years or Coronary artery disease or Crowded disc or low cup to disc ratio in the eye an eye disorder or Diabetes or Hyperlipidemia high fats in the blood or Hypertension high blood pressure or Non-arteritic anterior ischemic optic neuropathy or NAION serious eye condition , history of or Smoking—May increase the chance for a serious side effect in the eye called NAION.The Savings Offer and Program expire on 12/31/ For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS Eligible patients may save on their VIAGRA® (sildenafil citrate) prescription with the VIAGRA savings card.  · Description and Brand Names. Drug information provided by: Merative, Micromedex ®. US Brand Name. Revatio. Viagra. Descriptions. Sildenafil is used to treat . VIAGRA is supplied as blue, film-coated, rounded-diamond-shaped tablets containing sildenafil citrate equivalent to 25 mg, 50 mg, or mg of sildenafil. Tablets are debossed with PFIZER on one side and VGR25, VGR50 or VGR on the other to indicate the dosage strengths. Close.