Viagra: It is given in 90% of erectile dysfunction cases. Studies indicate that it helps 70% of patients achieve sexual function. A global satisfaction rate of 65% was achieve in one 1999 study. It was not a surprise that 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.
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. This regulates the 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.
Cialis: is a strong and highly-selective PDE5 inhibitor and may not affect other parts of the body, including the brain, heart, kidney and eyes. Clinical trials show significant success rates in up to 88% of patients. It appears to take effect in 15 minutes and the effects last up to 24 hours. Improved results were reported in men suffering from erectile dysfunction of varying severity and causes. Common side effects include headache, muscle pain, stomach upset following meals, and back pain.
Vardenafil : is another PDE5 inhibitor currently being investigated. A small study concluded that it increased penile rigidity and tumescence. More work is needed however.
