Does it work?


Can Epimedium act as a 'herbal Viagra'?


The release of Viagra in 1998 led to a sexual revolution of sorts. Suddenly, erectile dysfunction, or ED, was something men were allowed to talk about. Many men were reported to have the condition, and now something could be done about it. Sales of Viagra shot through the roof and soon similar pharmaceuticals were launched by competitors.

Herbal manufacturers were quick to add their products to the mix leading to a range of “herbal Viagra” products. One of the most popular came with a market-ready name: horny goat weed. The story is that, fadó fadó, a lonely goat herder in China noticed that his billy goats were particularly interested in the females after grazing in certain areas. He watched them carefully and saw that their interest peaked after eating a particular weed. This soon developed a reputation as an aphrodisiac and is now promoted for “sexual enhancement”.

The herbal remedy is made from several species of the genus Epimedium, with the extract usually called “epimedium”. Some claim it works like testosterone, leading to even more interest among body-builders. The evidence suggests otherwise.


A study published in 2008 examined several herbal remedies with reputations for increasing men’s sexual performance. They were tested against the enzyme that Viagra inhibits. Of all the herbs tested, only epimedium inhibited it. Hence the claims that epimedium is “herbal Viagra”.

The researchers purified the active ingredient from epimedium, which is called icariin. In its pure form, it is about 100 times less active than Viagra. Further research has chemically modified icariin to make more powerful derivatives. One of these has similar potency against the enzyme as Viagra. In addition, it does not cause some of the chemical reactions that give rise to some of Viagra’s side effects. Further research is being conducted on this compound.

Meanwhile, research is continuing on epimedium extract itself. Studies in animals have confirmed that it has similar effects to Viagra, though very much weaker. Studies in humans are very scarce. Four Chinese studies have been found, but only one used a control group. The other three simply asked participants if their sexual performance improved while taking the herb. Almost all the men said it did.

Such surveys provide weak evidence of effectiveness. Without a control group, it is impossible to know why the changes occurred. Simply being part of a study can be enough to produce changes, especially with a complex and subjective trait like sexual performance.


The herb seems to have few adverse effects, although very little information is available. Given that epimedium has Viagra-like effects, men with heart problems or taking heart medication should talk to their doctors before using epimedium.

Another serious problem is that herbal remedies sold for sexual enhancement are commonly contaminated. A 2009 study purchased 26 such products in the US. Fifteen contained one of the active pharmaceutical compounds like Viagra. Earlier this year, the UK Medicines and Healthcare products Regulatory Agency warned against using “herbal Viagra” products. In its own survey, it found that 65 per cent of such products were contaminated with pharmaceuticals, some containing higher doses than recommended for the medicines. Regulatory agencies have recently recalled specific products in the Netherlands, Canada, Australia, Singapore and Hong Kong.


In spite of horny goat weed’s widespread promotion, little is known about its effectiveness or safety. Some preliminary research suggests that pharmaceuticals made from the active ingredient in epimedium may be useful in treating ED. As with any new drug, extensive clinical trials are needed before it can be approved for use.

Horny goat weed is promoted as part of a culture focused on sexual performance. At a fraction of the cost, and without the need to talk to anyone, epimedium appears to offer a simple solution. However, ED can be a symptom of a serious underlying medical condition that should be medically evaluated. Also, purchasing “herbal Viagra” is clearly not safe given the high degree of adulterated products. This is especially problematic as those with ED often have heart conditions, which could be negatively affected by the adulterants.

Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007