They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. This site is intended only for U. Before starting, stopping, or changing any medications while taking sildenafil, please get the advice of your doctor or pharmacist. Shake the liquid well for 10 seconds before each use to mix the medication evenly. Ask your pharmacist for a list of the ingredients.You’ll typically take Viagra about 1 hour before sex. You can take the drug 30 minutes to 4 hours before you anticipate sexual activity. Based on how well you respond to this . Cost. Overdose. Ask your doctor. Q&A. Drug Images. What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription . VIAGRA can cause serious side effects. Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get .