If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Seven of these companies are based in India. This is a type of high blood pressure that occurs between the heart and the lungs. This development was credited largely “due to the introduction of generic products. Click here for an email preview. Continue to take sildenafil even if you feel well. Sildenafil belongs to a group of medicines called phosphodiesterase 5 PDE5 inhibitors.Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles . Sildenafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual stimulation, sildenafil works by increasing blood flow to .