Take sildenafil up to 4 hours before you want to have sex. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. At the same time, on-treatment function was better in treated patients who were less impaired at baseline. Percentage of Patients Reporting an Improvement in Erections. If you see air bubbles in the syringe, repeat the steps.The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 minutes to 4 hours before sexual activity. And you. VIAGRA is available by prescription only in 25 mg, 50 mg, and mg tablets. Patients should always ask their doctors for medical advice about adverse events. You are encouraged to report adverse events related to Viatris products by calling (U.S. only). If you prefer, you may contact the U.S. Food and Drug Administration (FDA. 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.