Oral treatments for Erectile dysfunction

Sildenafil (Viagra)

Sildenafil (Viagra) is now prescribed in over 90% of erectile dysfunction cases. Studies indicate that it helps 70% of patients achieve sexual function. In one 1999 study, overall male satisfaction was 65%. Not surprisingly, the best results occurred in men who had the fewest sexual problems before treatment, but even men with severe erectile dysfunction had a 41% satisfaction rate. A 2000 study of men who had responded well initially to sildenafil found that 96% of them were satisfied with the treatment after two to three years.

Administration and Effect. Sildenafil is effective within 20 to 40 minutes. The drug works only when the man experiences some sexual arousal. Patients usually take 50 mg, although lower doses (eg, 25 mg) may be appropriate in some groups, such as elderly patients. Sildenafil should not be used more than once a day and the dose should not exceed 100 mg. Used alone or in combination with penile injections, it may help men who did not respond to initial therapy with penile injections alone, but side effects can be quite intense when the combination is used.

Mechanism of Actions. Sildenafil was originally developed for heart disease, but was found to have a unique mechanism of action that targeted only factors in the penis. The drug blocks the enzyme phosphodiesterase-5 (PDE5). This action maintains persistent levels of cyclic GMP, a chemical that is produced in the penis during sexual arousal and which is the primary chemical that relaxes smooth muscles and increases blood flow.

Common Side Effects. Common side effects include the following:

• Flushing.
• Muscle aches.
• Gastrointestinal distress.
• Headache.
• Nasal congestion.

Other effects of Viagra have raised somewhat greater concern:

• Visual Effects. About 2.5% of men experience abnormal visual effects that include seeing a blue haze and temporary increased brightness. Experts believe that visual disturbances are related to the inhibition of phosphodiesterase enzymes, but the effect appears to be temporary and insignificant. Still, men at risk for eye problems and who take sildenafil regularly should have frequent eye examinations with an ophthalmologist.
• Dangerous Interaction with Nitrate Drugs. Taking sildenafil along with nitrates can cause a sudden and dangerous drop in blood pressure, and the effects have been fatal in some men. No one taking nitrates, including nitroglycerin or the street drug amyl nitrate, should take sildenafil. In men with normal blood pressure and in those taking other antihypertensive medication, sildenafil causes modest decreases in blood pressure and very small changes in heart rate, but does not appear to pose a significant risk.