Understand the formulation and mechanism of Revatio vs Viagra. This also indicates that Revatio can be effective in treating erectile dysfunction. While the amount of sildenafil per tablet is lower than Viagra, many men with mild or moderately severe ED find their condition is effectively treated with the 20-milligram dose found in Revatio. The best way to separate Viagra and Revatio is by dosage and what they’re typically prescribed for. Viagra is prescribed to men dealing with erectile dysfunction, while Revatio is FDA-approved to treat pulmonary arterial hypertension (PAH) — a type of high blood pressure in the lungs.