How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Some medications should not be taken with sildenafil. When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs. John’s wort. Recent heart or blood vessel problems. Use the oral syringe provided with your medication to measure and take your dose. Sildenafil belongs to a group of medicines called phosphodiesterase 5 PDE5 inhibitors.Descriptions Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase . 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 . Viagra – Uses, Side Effects, and More Generic Name (S): sildenafil Uses Sildenafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED).