Read and follow these instructions carefully before you start using sildenafil and each time you get a refill of your medicine. The dosage prescribed for you is based on your personal medical history and needs. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail. Different dosages all work the same way and last about hours, with mg being an effective dosage for men who don’t respond to lower doses. Children younger than 1 year of age—Use and dose must be determined by your doctor. If your dose is different, do not change it unless your doctor tells you to do so. Common ones include: Flushing of the skin.You shouldn’t take Viagra if you’re taking the pulmonary arterial hypertension (PAH)* drugs listed below. Taking Viagra with these medications can cause your blood . 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. However, the dose is . 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 .