This may take Viagra longer and not work as well as it should. Patients should always ask their doctors for medical advice about adverse events. This time may be as short as a few minutes in younger people and as long as a few hours or days in older adults. Is Viagra Safe in Females? Alternatives to Viagra PDE-5 inhibitors are the most common drug to treat erectile dysfunction.25 milligrams (mg) 50 mg mg Typical dosages The following information describes commonly recommended dosages for ED. However, be sure to take the dosage your . Viagra is available in three strengths: 25 milligrams (mg), 50 mg, and mg. What are the typical dosages of Viagra? Typically, your doctor will start you on the recommended . Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with .