Drugs for treating impotence can be taken orally, injected directly into the penis, or inserted into the urethra at the tip of the penis. Taken one hour before sexual activity, sildenafil works by enhancing the effects of nitric oxide, a chemical that relaxes smooth muscles in the penis during sexual stimulation, allowing increased blood flow. While sildenafil improves the response to sexual stimulation, it does not trigger an automatic erection as injection drugs do. The recommended dose is 50 mg, and the physician may adjust this dose to 100 mg or 25 mg, depending on the needs of the patient. The drug should not be used more than once a day.
Oral testosterone can reduce impotence in some men with low levels of natural testosterone.
Many men gain potency by injecting drugs into the penis, causing it to become engorged with blood. Nitroglycerin, a muscle relaxant, sometimes can enhance erection when rubbed on the surface of the penis. The system uses a pre-filled applicator to deliver the pellet about an inch deep into the urethra at the tip of the penis. An erection will begin within 8 to 10 minutes and may last 30 to 60 minutes. Research on drugs for treating impotence is expanding rapidly.