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. What special dietary instructions should I follow? Protein binding is independent of total drug concentrations. They might write a legitimate prescription for Viagra sildenafil , Cialis tadalafil or another treatment. The patients in studies had varying degrees of ED. Taking sildenafil alone will not cause an erection.Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the . In , a meta-analysis of trials determined that while Viagra is the most effective of the various ED drugs on the market, it also has the highest incidence of side effects—headache, upset stomach, vision loss, blue-tinged sight, back pain, muscle pain, nausea, and dizziness, just to name a few common ones. Sildenafil citrate is a white to off-white crystalline powder with a solubility of mg/mL in water and a molecular weight of VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and mg of sildenafil for oral administration.