One-third to one-half of the subjects in these studies reported successful intercourse at least once during a 4-week, treatment-free run-in period. If you prefer, you may contact the U. Results with all doses have been pooled, but scores showed greater improvement at the 50 and mg doses than at 25 mg. Protein binding is independent of total drug concentrations. Alpha-blockers are sometimes prescribed for prostate problems or high blood pressure. The most common side effects are headaches, feeling sick, indigestion and dizziness. Taking sildenafil alone will not cause an erection.In addition to Viagra, REX MD also offers brand-name Cialis and generic Cialis (tadalafil). Both Viagra and sildenafil are available in mg, mg, and mg doses. VIAGRA is supplied as blue, film-coated, rounded-diamond-shaped tablets containing sildenafil citrate equivalent to 25 mg, 50 mg, or mg of sildenafil. Tablets are debossed with PFIZER on one side and VGR25, VGR50 or VGR on the other to indicate the dosage strengths. Close. VIAGRA contains sildenafil, which is the same medicine found in another drug called REVATIO. REVATIO is used to treat a rare disease called pulmonary arterial hypertension (PAH). VIAGRA should not be used with REVATIO or with other PAH treatments containing sildenafil or any other PDE5 inhibitors (such as Adcirca [tadalafil]).