Matthew Ziegelmann, a urologist at Mayo Clinic. This medication is taken with or without food an hour before sex. Cardiovascular disease: One of the earliest signs of heart disease is the inability of blood vessels in the penis to enlarge, allowing enough blood flow to get and maintain an erection. In this video, we’ll cover the basics of erectile dysfunction. We wish you well.Some people may get a headache after taking Viagra. In studies, this was a common side effect of the drug. Most headaches are mild and go away quickly. which can make it hard to breathe; What. 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 . Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP.