For some, the cause is psychological, but for many others, especially older men, erectile dysfunction usually has a physical source, such as diseases including diabetes, injury or side effects of medications, according to the NKUDIC Web site.
In the late 1990s, the launch of the drug Viagra revolutionized treatment of impotence. The drugs Levitra and Cialis followed. All three medications enhance the effects of nitric oxide, a chemical that relaxes smooth muscles in the penis during sexual stimulation and allows increased blood flow.
The spider venom also works to increase nitric oxide levels but through a different mechanism, Nunes said. Scientists are a long way from using the venom as the basis of a new erectile dysfunction medication, but they are hopeful, said Nunes.
"We do need more research," she added. "I'm sure it can be a pharmacological tool that may one day be able to help patients who cannot take Viagra."
One noted researcher expressed interest in Nunes' work.
"The concept that a venom can have an effect on erection is highly plausible," said Dr. Arnold Melman, chief of urology at Montefiore Medical Center in New York City. "This is very interesting and exciting, but also very early."
The U.S. National Kidney and Urologic Diseases Information Clearinghouse has more on erectile dysfunction.
SOURCES: Kenia Pedrosa Nunes, Ph.D., Medical College of Georgia, Augusta; Arnold Melman, M.D., professor, medicine, Albert Einstein College of Medicine, New York City; National Kidney and Urologic Diseases Information Clearinghouse, Bethesda, Md.; American Heart Association, news release, Sept. 24, 2009
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