Horny Goat Weed
(Epimedium)

What is horny goat weed? It is a leaf from the Japanese epimedium (Epimedium grandiflora). Other species of Epimedium are also used.

In traditional Chinese medicine (TCM), this herb is used to support the liver and kidney, build bone and muscle and as a bodybuilding supplement. It is often combined with other herbs as is often the case in TCM.

Epimedium contains many active ingredients. The ones believed to show the most promise are icariin, genistein and daidzein, a type of plant-based estrogen (female hormone).

One study shows that a specific formulation of epimedium reduced bone loss in postmenopausal women after 24 months of treatment.

The remaining information came from animal studies or studies done in vitro (on tissue samples in a test tube). In animals, epimedium seems to increase semen secretion, lower blood pressure and increase blood flow to the tissue responsible for allowing erection of the penis to occur (behaving much like what Viagra does).

“Dell'Agli and his colleagues tested the four plants in vitro to see how efficient they were at inhibiting PDE5. Just one - Epimedium brevicornum, also known as horny goat weed and Bishop's Hat - had an effect. This confirmed previous studies showing that icariin, a compound found inside the horny goat weed, is a PDE5 inhibitor."

As reported from the magazine New Scientist: "Viagra's active compound, sildenafil, works by inhibiting an enzyme called phosphodiesterase-5 (PDE5). Because PDE5 helps control blood flow to the penis, inhibiting PDE5 promotes male erection.

There are several research studies in animals that suggest epimedium might thin the blood like Aspirin and increase blood flow to the heart. As well, epimedium seems to stimulate the immune system and research suggests that it might be effective against the AIDS/HIV virus. It also seems to have some effects like the female hormone estrogen.

Side effects reported in research studies include nausea, vomiting, dizziness and dry mouth.

Do not overdose on epimedium as it may cause breathing difficulties and possibly cause the heart to beat very fast (tachyarrhythmia). Overdose might cause muscle spasm and co-ordination problems.

Safety - In one research study, an extract containing 60 mg of icariin was used in humans for 2 years.

In theory, it is possible for epimedium to cause the effects of Aspirin and blood-thinners like warfarin to be enhanced. Consult with your healthcare provider before starting or stopping epimedium.

In theory, epimedium might decrease blood pressure. This might be a possible concern in those people who already have low blood pressure. Monitor blood pressure when starting or stopping epimedium.

If you have an existing heart condition (e.g. heart attack, stroke), consult with your healthcare provider first before starting epimedium

Raw Herb: Dosage of 6 to 15 grams daily have been used.

Tincture: Take 5 mL (1 teaspoon) of a 20% tincture three times daily.

Decoction: Simmer 5 grams of the herb in about 1 cup (250 mL) of water for 15 minutes. Drink three times daily.

The only available data on dosage of epimedium is from the osteoporosis study. That particular formulation contained 60 mg icariin, 15 mg daidzein and 3 mg genistein.

What is the expected time it takes to get results after a dose of the epimedium supplement? There is no research study done to determine this but we may hypothetically expect similar result as with Viagra as epimedium works similarly to Viagra.

It is best to take it at least 1-2 hours prior to the expected time of sexual intercourse.

There is no info on how effective the tea extract would work compared to the pill formulation.

Does the epimedium cross the skin? We don't know. If not, then the gel formulation would probably have no effect. Avoid the gel formulation and choose the pill form instead.

Selected References for Horny Goat Weed
Revised: January 4, 2010