Horny Goat Weed Epimedium spp.
Mainly: E. brevicornu Maxim.; E. koreanum Nakai; E. pubescens Maxim.; E. sagit-
tatum (Siebold & Zucc.) Maxim. Other species of Epimedium are used medicinally,
including E. acunatum Franch and E. wushanense T.S.Ying (as unofcial substitutes
of Epimedii herba)
Synonyms: Aceranthus macrophyllus Blume ex. K.Koch; A. sagittatus Siebold &
Zucc. (=E. sagittatum)
Other common names: Barrenwort; bishop’s hat; epimedium; yin yang huo
Drug name: Epimedii herba
Botanical drug used: Aerial parts
Note: Based on the large number of species accepted in the Pharmacopoeia of
China, in combination with the poor information that is generally available about
the quality of products sold as horny goat weed, there can be no evidence-based
use of a product with an acceptable quality. Therefore, it clearly cannot be
recommended by a health care professional.
Indications/uses: To treat sexual dysfunction, particularly impotence in men
and lack of libido in women. In traditional Chinese medicine, it is also used
widely for osteoporosis. Epimedium species are used to treat a number of
other conditions including rheumatic arthritis, menopausal symptoms and
Evidence: There is limited evidence to support the use of epimedium to treat
sexual dysfunction and osteoporosis, although it is known to contain potent
Safety: Tests in animal models have shown no serious toxicity issues, but human
clinical safety has not been established. Epimedium should not be used con-
currently with other phosphodiesterase-5 (PDE-5) inhibitors, or when PDE-5
inhibitors are contraindicated (e.g. cardiac arrhythmias), or during pregnancy
Main chemical compounds: The main active constituents are the prenylated
avonoids, icariin and its metabolites, epimedins A, B, C, and the sagittatosides.
Phytopharmacy: An evidence-based guide to herbal medicinal products, First Edition.
Sarah E. Edwards, Inês da Costa Rocha, Elizabeth M. Williamson and Michael Heinrich.
© 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd.
Horny Goat Weed 211
Other active compounds present include avonol glycosides (of kaempferol,
quercetin, myricetin); avones (tricin, luteolin); biavones (gingketin, isogingketin,
bilobetin); lignans such as syringaresinol; alkaloids (e.g. epimediphine from
E. koreanum); β-sitosterol (E. sagittatum,E. brevicornu); and a chalcone, isoliquir-
itigenin (from E. koreanum) (Ma et al. 2011; Pharmaceutical Press Editorial Team
2013; Zhang et al. 2013c).
Sexual dysfunction: Limited clinical data are available on the effects of epimedium
on erectile dysfunction. A small double-blind clinical trial was reported assessing
an epimedium herbal complex supplement in 25 healthy men and 13 men who had
used sildenal (Viagra). The men were administered with the herbal complex for a
minimum of 45 days. Daily use of the epimedium preparation was found to enhance
sexual satisfaction to a greater extent than sildenal (Ma et al. 2011).
Bone health and osteoporosis in menopause: A ve-year follow-up study of a
herbal preparation of epimedium for prevention of postmenopausal osteoporosis
and fragility fractures found that it was able to reduce postmenopausal bone loss,
and also showed some potential for reduction in fragility fracture incidence (Deng
et al. 2012). A randomised, double-blind placebo-controlled clinical study in 85
postmenopausal women with osteopenia (lower than normal mineral bone density,
considered a precursor to osteoporosis), were treated with icariin 60mg, combined
with the isoavonoids daidzein 15 mg, and genistein 3mg, daily for 24 months. All
patients were also given calcium 300 mg daily. A statistically signicant, though
small, increase in bone density was found in the test group and bone resorption
markers were signicantly decreased, compared to the control group (Zhang et al.
2007). Isoavones are oestrogenic and so also have osteogenic activities.
Other oestrogenic effects: A study evaluating the effects of Epimedii herba water
extract on blood lipid and sex hormone levels in 90 postmenopausal women found
that after 6 months of medication, the extract decreased total cholesterol and triglyc-
eride levels (p<0.01) and signicantly increased serum levels of oestradiol, com-
pared with the pre-treatment level (Yan et al. 2008).
Pre-clinical evidence and mechanisms of action:
Sexual dysfunction: Icariin has erectogenic properties in animals, via phosphodi-
esterase type 5 (PDE-5) inhibition, and also neurotrophic effects in vitro and in vivo
(Shindel et al. 2010). A study in male rats found increased sexual behaviour after
treatment with epimedium in combination with four other medicinal plants. How-
ever, individual assessment of the herbs showed no improvement, indicating a pos-
sible synergistic action between them (Zanoli et al. 2008). A study in isolated rabbit
corpus cavernosum (CC) smooth muscle showed that epimedium extracts could
elicit a relaxation effect through activation of multiple targets on NO/cGMP sig-
nalling pathways. The study also found that they potentiated the effects of PDE-5
inhibitors (commonly used for erectile dysfunction), such as sildenal and varde-
nal. The crude extracts were found to have a greater potency than the puried
compounds (Chiu et al. 2006).
Bone health and osteoporosis: Icariin is involved in the regulation of multiple
signalling pathways in osteogenesis, anti-osteoclastogenesis, chondrogenesis, angio-
genesis and inammation. It has been reported to have the potential to be used as
a substitute for osteoinductive protein-bone morphogenetic proteins, or to enhance
their therapeutic effects, for bone tissue engineering as well as treatment of osteo-
porosis (Zhang et al. 2013b).
Other relevant effects: Icariin has phytoestrogenic properties and has been shown
to promote the biosynthesis of oestrogen by aromatase (Yang et al. 2013). It reduced
the levels of serum total cholesterol and low-density lipoprotein cholesterol, and
reduced platelet adhesiveness and aggregation in atherosclerotic rabbits, demon-
strating lipid-lowering effects (Zhang et al. 2013a). The alkaloid epimediphine has
anticholinesterase activity (Zhang et al. 2013c), which together with the oestrogenic
effects of other constituents, may support the use for memory enhancement.
Interactions: There is conicting evidence about a possible interaction with other
PDE-5 inhibitors such as sildenal (Viagra). In vitro evidence has suggested that
epimedium potentiates PDE-5 inhibitors (Chiu et al. 2006), but a study of the effects
of E. sagittatum extract on the pharmacokinetics of sildenal demonstrated that the
area under the concentration–time curve of sildenal was signicantly decreased
in groups that received a high dose of epimedium extract, suggesting antagonistic
effects (Hsueh et al. 2013). Co-administration with PDE-5 inhibitors should, there-
fore, be avoided until further information is available.
Another in vitro study found that epimedium is a potent inhibitor of cytochrome
P450 isoforms (including CYP1A2, CYP2C19, CYP2E1, CYP2C9, CYP3A4,
CYP2D6) and NADPH-CYP reductase, indicating a possible potential for inter-
action with other drugs, although the clinical signicance is not known (Liu et al.
Contraindications: Epimedium should not be used during pregnancy and lacta-
tion as it has oestrogenic activity. Paediatric use is not appropriate. People with heart
conditions should avoid using epimedium and long-term use is not recommended
(Pharmaceutical Press Editorial Team 2013).
Adverse effects: In high doses (not specied), epimedium may have a stimulatory
effect and cause sweating or a feeling of heat. Prolonged use of excessive amounts
in animal studies was associated with decreased thyroid activity (Ma et al. 2011).
A case was reported of a 66-year-old man who developed heart arrhythmia
and hypomania after taking a herbal sexual enhancement product containing
epimedium. As it was a multi-ingredient preparation, and the man was predisposed
to heart disease and possible mood disorder, it is unclear if this was caused by
epimedium or another ingredient (Partin and Pushkin 2004).
Dosage: For products, see manufacturers’ instructions. For the herb, the adult dose
is 3–9 g dried aerial parts daily (Pharmaceutical Press Editorial Team 2013).
General plant information: According to a Chinese legend, a goat herder rst
noticed the qualities of the plant after he observed far more sexual activity in his
goats after they ate it; hence the common name (Ma et al. 2011).
Chiu J-H, Chen K-K, Chien T-M, Chiou W-F, Chen C-C, Wang J-Y, Lui W-Y, Wu C-W.
(2006) Epimedium brevicornum Maxim extract relaxes rabbit corpus cavernosum through
multitargets on nitric oxide/cyclic guanosine monophosphate signaling pathway. Interna-
tional Journal of Impotence Research 18(4): 335– 342.
Horny Goat Weed 213
Deng WM, Zhang P, Huang H, Shen YG, Yang QH, Cui WL, He YS, Wei S, Ye Z, Liu F,
Qin L. (2012) Five-year follow-up study of a kidney-tonifying herbal Fufang for preven-
tion of postmenopausal osteoporosis and fragility fractures. Journal of Bone and Mineral
Metabolism 30(5): 517– 524.
Hsueh TY, Wu YT, Lin LC, Chiu AW, Lin CH, Tsai TH. (2013) Herb-drug interaction of
Epimedium sagittatum (Sieb. et Zucc.) maxim extract on the pharmacokinetics of sildenal
in rats. Molecules 18(6): 7323– 7335.
Liu KH, Kim MJ, Jeon BH, Shon JH, Cha IJ, Cho KH, Lee SS, Shin JG. (2006) Inhibition
of human cytochrome P450 isoforms and NADPH-CYP reductase in vitro by 15 herbal
medicines, including Epimedii herba. Journal of Clinical Pharmacology and Therapeutics
31(1): 83– 91.
Ma H, He X, Yang Y, Li M, Hao D, Jia Z. (2011) The genus Epimedium: An ethnopharma-
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horny goat weed (Epimedium spp.)in vitro and in vivo.Journal of Sexual Medicine 4(Pt 1):
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and improves lipid metabolism in postmenopausal women. Phytotherapy Research 22(9):
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cornum Maxim promotes the biosynthesis of estrogen by aromatase (CYP19). Journal of
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Zanoli P, Benellia A, Zavatti M, et al. (2008) Improved sexual behaviour in male rats treated
with a Chinese herbal extract: hormonal and neuronal implications. Asian Journal of
Andrology 10(6): 937–945.
Zhang G, Qin L, Shi Y. (2007) Epimedium-derived phytoestrogen avonoids exert benecial
effect on preventing bone loss in late postmenopausal women: a 24-month randomized,
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Zhang WP, Bai XJ, Zheng XP, Xie XL, Yuan ZY. (2013a) Icariin attenuates the enhanced
prothrombotic state in atherosclerotic rabbits independently of its lipid-lowering effects.
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Zhang X, Liu T, Huang Y, Wismeijer D and Liu Y. (2013b) Icariin: does it have an osteo
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Zhang X, Oh M, Kim S, Kim J, Kim H, Kim S, Houghton PJ, Whang W. (2013c)
Epimediphine, a novel alkaloid from Epimedium koreanum, inhibits acetylcholinesterase.
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