Revatio® is used to treat a uncommon illness identified as pulmonary arterial hypertension (PAH). Viagra® and generic Viagra® shouldn't be applied with Revatio® or with other PAH alternatives made up of sildenafil or some other PDE5 inhibitors (for instance Adcirca [tadalafil])are allergic to sildenafil, as contained in Viagra® and Revatio, or