They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. This medication is taken with or without food an hour before sex. Do not drink grapefruit juice if you’re taking sildenafil Revatio for pulmonary hypertension. Often, these are prescribed for chest pain called angina. This boosts blood flow and helps you get an erection from sexual activity.Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve . What does Viagra do for ED? Viagra works to treat ED by helping you have and maintain an erection. The drug does this by improving blood flow into your penis when . Since , Viagra (sildenafil) has been used for treating erectile dysfunction (ED). It’s available by prescription for males ages 18 years and older. Side effects are .