Spider Venom -- The Next Way to Treat Impotence?

FRIDAY, Sept. 25 (HealthDay News) -- Scientists may have discovered a novel way to treat erectile dysfunction -- using the venom of a deadly spider.

The bite from the Brazilian wandering spider (Phoneutria nigriventer) causes a painful erection that can last for many hours and later lead to impotence, researchers from the United States and Brazil noted.

After isolating the toxin, the researchers radioactively labeled and injected a purified form of the toxin, Tx2-6, into rats that suffered from high blood pressure and severe erectile dysfunction. The investigators then measured the presence of the toxin in the animals' penises and used the toxin to contract and relax strips of penile tissue. Results showed improved levels of nitric oxide, which led to penile relaxation and erections.

The researchers were scheduled to present their work Sept. 24 at the American Heart Association's conference on high blood pressure research in Chicago.

"In Brazil, it's common to have accidents with poisonous animals," explained lead researcher Kenia Pedrosa Nunes, a post-doctoral fellow in physiology at the Medical College of Georgia in Augusta and a native of Brazil. "So, we were aware of this spider's venom. The toxin was able to normalize erections [in rats]."

Brazilian wandering spiders are found throughout Central and South America. They are considered the world's most venomous spider, causing an unknown number of human deaths.

Erectile dysfunction, also known as impotence, has many causes and a growing body of treatments. According to the National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC), erectile dysfunction "can be a total inability to achieve erection, an inconsistent ability to do so, or a tendency to sustain only brief erections." The condition affects as many as 30 million American men at some point in their lives.

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."

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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