Proper Use Use sildenafil exactly as directed by your doctor. You can take it up to 4 hours before you want to have sex. How should this medicine be used? VIAGRA was evaluated primarily at doses of 25 mg, 50 mg and mg in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in duration, using a variety of study designs fixed dose, titration, parallel, crossover. Children—Use is not recommended.Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in test1.ru is also used to treat pulmonary arterial hypertension, a serious heart and lung test1.ru drug is more popular than comparable drugs. It is available in generic and brand versions. Generic sildenafil is covered by most Medicare and insurance plans, but . About sildenafil (Viagra) Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs). If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when. It really depends based on the person. Most of the time, Viagra starts to work after 30 minutes. Some people note that Viagra works faster when taken on an empty stomach. The effects of Viagra usually last around 4 See more.