They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. This medicine has been approved in the United States to treat premenopausal females who have low sexual desire. In pulmonary hypertension it works by relaxing blood vessels in the chest. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when you get sexually excited. Sildenafil may cause side effects. It might work longer if you have mild to moderate erectile dysfunction. · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where this enzyme works. Fact is, 85% of CVS® prescriptions are under $10 per month. See details.* Ready to find out more? Compare cost-saving options. Two great savings options. Search for lower drug . MinuteClinic can treat over different conditions. Find a walk in location near you today.