However, the dose is usually not more than 80 mg 3 times a day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. If your dose is different, do not change it unless your doctor tells you to do so. 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. Sildenafil Viagra comes in tablets and prescriptions are available in increments from 20 to mg doses.Last updated on Uses Warnings Before taking Dosage Side effects Interactions FAQ What is sildenafil? Sildenafil relaxes muscles of the blood vessels and .  · Revatio Viagra Descriptions Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines .  · For oral dosage forms (suspension or tablets): Adults—20 milligrams (mg) 3 times a day. Your doctor may adjust your dose as needed and tolerated. .