Sildenafil (Viagra) and Revatio (PAH) Sildenafil is a medication used to treat erectile dysfunction in men (Viagra brand) and pulmonary arterial hypertension in women and men (Revatio brand). Sildenafil works by blocking an enzyme that breaks down cGMP, a substance that promotes muscle relaxation and blood vessel dilation. This medication is not recommended for use with nitrate medications (eg,...