Horny Goat Weed, also known as epimedium, has been in use as an aphrodisiac for centuries by the Chinese. Some also consider it a treatment option for menopause. According to legend, a goat herder noticed increased libido in his herd after they consumed a plant that came to be called horny goat weed. Horny goat weed is sold as a health supplement, in raw form or as a tablet or capsule. The amount of time it takes for horny goat weed to work is difficult to determine. Depending on the validity placed in the information, it can have the desired effect in as little as 30-90 minutes. Some sources claim the effects can last as long as a week.
Icariin, the active ingredient in horny goat weed, does show in some test studies an ability to inhibit the PDE-5 enzyme. Sildenafil, the active ingredient in Viagra, has been shown in those same studies to be as much as 80 times more effective. Researchers at the University of Milan, Italy prepared five separate variations of a compound containing icariin. The fifth compound was shown in their research to be as effective as Viagra. Preliminary tests indicate that the so-called "compound 5" might not have the same negative side effects of Viagra (patients with heart problems are recommended to avoid Viagra because it sometimes has adverse affects to eyesight in those patients).
Recommended dosage is approximately 500 milligrams of horny goat weed per capsule. Typically these products are standardized with 10% Icariin. Two to four capsules per day is the suggested intake.
Animal studies reviewed by About.com's medical board show horny goat weed may increase nitric oxide levels, which has the function of relaxing smooth muscle tissue and allows more blood flow to the penis or clitoris. It appears to inhibit the PDE-5 enzyme, which is how Viagra works. There is evidence that horny goat weed may be able to restore to normal levels the hormones cortisol, testosterone and thyroid.
Lengthy clinical trials are needed before "compound 5" would be approved as a viable drug. This may keep the compound off the marketplace for as long as another ten years. Meanwhile, University of Milan researchers concluded that while there may be some benefit to consumption of horny goat weed, it will not be as effective as Viagra.
Animal studies indicate that higher doses of the compound Icariin, the active ingredient in horny goat weed, can be toxic to the liver and kidneys. No significant drug interactions have been noted.