Take sildenafil at around the same times every day. Those with pre-existing conditions should always consult a healthcare provider before taking new medications or supplements. You are encouraged to report adverse events related to Viatris products by calling U. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Stendra avanafil : This is an as-needed medication taken 30 minutes before sex and can last up to six hours. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Those who don’t feel comfortable discussing ED with an in-person provider or lack time to visit a doctor’s office may find online ED prescriptions beneficial. · Do not take more than one dose of Viagra per day. Doing this can increase your risk for serious side effects. Missed dose. Viagra isn’t a medication you take every day. You’ll only take a dose. Used for Erectile Dysfunction. Sildenafil (Viagra) is taken by mouth to treat erectile dysfunction (ED). You take it only as needed, typically about an hour before sexual activity (but you can take it anywhere between 30 minutes to 4 hours before sex). Don’t take sildenafil (Viagra) more than once a day because doing so can put you at higher. 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 adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the .