Erectile Dysfunction Drugs Affect Other Systems, Mostly for the Better

Since the Food and Drug Administration gave Viagra® (sildenafil) its approval in 1998, "erectile dysfunction" has become a household term - probably to the chagrin of many parents fielding questions from their kids watching TV. But with sildenafil and the subsequent introduction and marketing of Levitra® (vardenafil) and Cialis® (tadalafil), many men have found answers to a once-unmentionable condition.

"As more and more patients seek therapy for sexual dysfunction, it is increasingly important for clinicians in a wide range of specialties to become proficient in the mechanisms and systemic effects of these medications," said Ernst R. Schwarz, M.D., Ph.D., a cardiologist at Cedars-Sinai Medical Center who specializes in therapies for men who suffer from erectile dysfunction (ED) and have heart problems, diabetes, high blood pressure or other related conditions.

Schwarz and colleagues recently concluded a review of the medical literature, as well as their own research findings and clinical data, to determine what actually is known about the effects of long-term use of this class of drugs on various organ systems. Their findings appears in the June 8, 2006 issue of the International Journal of Impotence Research.

Studies so far suggest the drugs, called phosphodiesterase-5 inhibitors (PDE-5i), produce mostly beneficial results, and not just for erectile dysfunction. The FDA recently approved a reformulation of sildenafil for the treatment of primary pulmonary hypertension, a disease that tends to occur in young women, causing elevated blood pressures in the lung that can lead to heart failure and early death.

"When we look at all the different organ systems - the blood, the heart, the lungs, blood flow in the brain - there are hardly any negative side effects. In fact, just the opposite is true. There are beneficial effects for primary pulmonary hypertension, as well as for conditions such as heart failure and lack of oxygen in the heart," said Schwarz. "The only issue is that the data we have are from relatively short-term studies. Viagra has been on the market since 1998 and the other two PDE-5 inhibitors were approved by the FDA in 2003. Therefore, we do not have multi-year follow-up studies. On the other hand, the drugs have been on the market for several years now and there have been no reports of negative long-term effects."

While there are some differences among the three medications, they have many properties in common and work by limiting the activity of the enzyme phosphodiesterase-5, which is found in tissues and vessels of the penis, blood platelets, and smooth muscle of blood vessels. For the treatment of erectile dysfunction, the drugs' constraint of the enzyme's action results in increased levels of cyclic guanosine monophosphate (cGMP) and nitric oxide (NO), biochemicals that promote smooth muscle relaxation and increased blood flow in erectile tissue.

According to the article, PDE-5 inhibitors can be effective in treating erectile dysfunction even for many men who also have diabetes, those who are older, and those who have co-existing ischemic heart disease (reduced blood flow to the heart caused by plaque buildup in the arteries). Furthermore, say the authors, "since PDE-5 is found in smooth muscles of the systemic arteries and veins throughout the body, use of PDE-5i has been associated with various cardiovascular effects."