Yin Yang Huo
StarEpimedium brevicornu Maxim.
Traditionally used for
- Urinary & fluids
- Fertility & vitality
- Pain & joints
- Energy & fatigue
Cautions & contraindications
- Bleeding disorders
- Heart conditions
- Liver conditions
☯ TCM Properties
Tonifies Kidney Yang; Strengthens the Sinews and Bones; Dispels Wind-Dampness; Warms the Ming Men Fire
Traditional Chinese Uses
Yin Yang Huo (epimedium, Horny Goat Weed) is a pungent, sweet, warm herb known for powerfully supplementing Kidney Yang and essence, expelling Wind-Cold-Damp, and strengthening bone. It is widely used for impotence, infertility, cold and weak lower back and knees, and urinary frequency from Kidney Yang deficiency. It also addresses joint and bone pain from Wind-Cold-Damp obstruction. Its contemporary fame as a natural aphrodisiac derives from this longstanding Yang-tonifying tradition.
Western Herbalism Properties
Used In Formulas (1)
Relationships
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Botanical Description
Epimedium brevicornu is a low-growing perennial herb in the Berberidaceae family, native to central and northern China, where it occurs in mountain woodlands and rocky slopes. It grows 20-50 cm tall from a slender, branching rhizome, producing tufts of long-petioled basal leaves and similar stem leaves. Each leaf is typically twice ternately compound, with leaflets that are ovate to cordate, 3-7 cm long, with finely serrate, bristly margins and an asymmetric, often heart-shaped base; new growth is bronze-tinged. In spring, slender panicles bear small, distinctive white flowers with four spurred petals giving a delicate, downward-facing form. In TCM, the dried leaves (Yin Yang Huo) are used as an acrid, sweet, warm herb that tonifies kidney yang, strengthens sinews and bones, and dispels wind-damp.
Active Constituents
Icariin
Prenylated flavonol glycosideThe indicative constituent of the genus and the compound behind most of the herb's pharmacology. It is a genuine phosphodiesterase-5 inhibitor: against human recombinant PDE5A1 its IC50 is 5.9 micromolar, and Epimedium brevicornum extract gave 80% inhibition at 50 micrograms/mL, the only extract active in a panel that also included Tribulus terrestris, Ferula hermonis and Cinnamomum cassia. It also inhibits UGT1A3 potently. Its potency is far below sildenafil's, roughly 80-fold weaker than a semisynthetic derivative that matches sildenafil, so the mechanism is real but the herb is not a substitute for a licensed PDE5 inhibitor.
Epimedin A
Prenylated flavonol glycosideOne of the three epimedins assayed with icariin as quality markers for Herba Epimedii, and separable from icariin from Epimedium brevicornum root material by high-speed counter-current chromatography. Contents of the epimedins differ substantially between Epimedium species, which is one reason species-blind dosing of this herb is unsatisfactory.
Epimedin B
Prenylated flavonol glycosideIsolated from Epimedium brevicornu and shown to specifically facilitate nigericin- or ATP-induced NLRP3 inflammasome activation under synergistic induction of mitochondrial reactive oxygen species, with caspase-1 activation and IL-1beta secretion in a lipopolysaccharide-sensitised mouse model, all abolished by the NLRP3 inhibitor MCC950. It is therefore a candidate mediator of the idiosyncratic liver injury reported with this herb, and has separately been named among its principal hepatotoxic constituents. Immunostimulatory activity and hepatotoxic risk are, for this compound, the same property.
Epimedin C
Prenylated flavonol glycosideThe third epimedin marker, quantified with icariin in pharmacopoeial and near-infrared assays of the drug and in pharmacokinetic studies of Epimedium total flavonoids.
Icariside II (baohuoside I)
Prenylated flavonol glycoside (intestinal metabolite of icariin)A major intestinal metabolite of icariin and, with icariin, one of the two constituents most often credited with the herb's anticancer activity. Its enzyme-inhibition profile differs from the parent compound's: it is a potent inhibitor of UGT1A4, UGT1A7, UGT1A9 and UGT2B7, so the interaction risk of this herb is created partly downstream of absorption rather than by icariin itself.
Icaritin
Prenylated flavonol aglycone (metabolite of icariin)The aglycone metabolite. It shows consistent anti-fibrotic activity in preclinical liver models through dual inhibition of HIF-1alpha and TGF-beta/Smad signalling, and it inhibits UGT1A7 and UGT1A9. In vivo it undergoes isopentenyl dehydrogenation, glycosylation and glucuronidation, and its intermediate metabolites are the suspected reactive species in the herb's hepatotoxicity, which is why the same molecule appears in the literature as both hepatoprotective and hepatotoxic.
Sagittatoside A
Prenylated flavonol glycosideNamed alongside epimedin B and icariside I as one of the primary hepatotoxic constituents of Epimedii Folium in network toxicology work with HepG2 validation. Not a quality-control marker, so a batch that passes the icariin assay says nothing about its content.
⚠ Drug Interactions
Undeclared sildenafil, tadalafil, vardenafil and their analogues in Epimedium and 'horny goat weed' products
This is the single most important hazard attached to this herb in commerce, and it is not theoretical. In a tiered bioassay-plus-LC-MS/MS study of 40 herbal sexual-performance supplements, significant amounts of sildenafil were found in 10 samples, vardenafil in 2 and tadalafil in 1, with estimated daily intakes above 25 mg sildenafil equivalents and six supplements above 100 mg sildenafil equivalents. Only one sample contained the natural constituent icariin at all, at 0.013 mg/g, far too low to explain the observed PDE5 potency, and further work on a discordant sample identified hydroxythiohomosildenafil, an analogue absent from the reference library. Products declaring Epimedium or horny goat weed have been the subject of recalls for undeclared sildenafil and propoxyphenylsildenafil. Dozens of sildenafil analogues of unknown safety circulate as adulterants.
Clinical note: Do not accept an over-the-counter 'horny goat weed' product as equivalent to prescribed Herba Epimedii. Ask any patient reporting sudden vasodilatory symptoms, visual disturbance or a hypotensive episode on a supplement what they took and keep the container. Patients on nitrates or alpha-blockers should be told plainly not to use these products, because the risk lies in what is not on the label.
Nitrates and nitric oxide donors (nitroglycerin, isosorbide mononitrate and dinitrate, nicorandil, amyl nitrite)
The mechanism is the same one that makes nitrates an absolute contraindication to licensed PDE5 inhibitors. Icariin inhibits PDE5A1 with an IC50 of 5.9 micromolar and whole Epimedium brevicornum extract inhibits it 80% at 50 micrograms/mL, so cGMP accumulation in vascular smooth muscle is amplified by the same pathway a nitrate loads. The herb's own potency is much lower than sildenafil's and no human haemodynamic study of the combination exists, which is why this is Possible rather than Established for the authentic drug. The reason to treat it as Major anyway is that Epimedium products are a documented vehicle for undeclared sildenafil at full or supratherapeutic doses, so a nitrate-treated patient taking one may be taking the interacting drug itself.
Clinical note: Treat Yin Yang Huo as contraindicated in patients on any nitrate or nicorandil, and in patients who might be given nitrates acutely for chest pain. Record its use prominently so an emergency department does not give nitrates blind.
Sildenafil, tadalafil, vardenafil, avanafil and other PDE5 inhibitors
Two mechanisms stack. Pharmacodynamically, icariin and the whole Epimedium brevicornum extract inhibit human PDE5A1 directly. Pharmacokinetically, a rat study of Epimedium sagittatum extract given for three days before intravenous sildenafil found the sildenafil AUC significantly decreased at the high extract dose, and the authors concluded that co-administration should be prevented; a companion study found an interaction with dapoxetine. Note the species: that pharmacokinetic work used Epimedium sagittatum, not Epimedium brevicornu, and the direction of the AUC change was downward, so the practical consequence is unpredictable exposure rather than a simple increase.
Clinical note: Do not combine. If a patient on a prescribed PDE5 inhibitor wants the herb for a kidney-yang indication, treat them as alternatives and not as a stack, and warn about priapism and hypotension if they overlap.
Hepatotoxic drugs and other liver-injury-associated agents, including Psoralea corylifolia fruit (Bu Gu Zhi) in the same prescription
Epimedii Folium is one of the better-documented Chinese herbal causes of idiosyncratic drug-induced liver injury. A clinical case of herb-induced liver injury from Xianling Gubao, an Epimedium-containing preparation, was worked up with the updated RUCAM causality method and an integrated evidence chain after excluding viral, alcoholic and autoimmune causes. Mechanistically the injury is immune-mediated rather than dose-linear: epimedin B facilitates NLRP3 inflammasome activation with caspase-1 and IL-1beta release in a lipopolysaccharide-sensitised model, and sagittatoside A, epimedin B and icariside I have been identified as the primary hepatotoxic constituents. The combination of Epimedii Folium with Psoraleae Fructus, a very common clinical pair, has an increasing number of associated liver injury reports and aggravates injury in an idiosyncratic-injury model.
Clinical note: Take a baseline ALT and AST before a prolonged course, and repeat at four to eight weeks. Avoid combining Yin Yang Huo with Bu Gu Zhi in a patient with any liver risk factor. Stop the herb and check liver function on new fatigue, nausea, dark urine, pruritus or jaundice, and do not restart it. Because the injury is idiosyncratic, a previously tolerated batch and a normal icariin assay are not reassurance.
UGT substrates with narrow margins (e.g. mycophenolate mofetil, lamotrigine, zidovudine, raloxifene)
Against a panel of recombinant human UGT isoforms, icariin potently inhibited UGT1A3, icariside II inhibited UGT1A4, UGT1A7, UGT1A9 and UGT2B7, and icaritin inhibited UGT1A7 and UGT1A9. Quantitative prediction from those data indicated that in vivo inhibition of intestinal UGT1A3, UGT1A4 and UGT1A7 would likely occur after oral administration of icariin-containing products. This is a first-pass intestinal effect, so it applies to oral dosing and to the metabolites formed in the gut, not only to icariin as ingested.
Clinical note: Where a UGT-cleared drug has a narrow therapeutic margin, monitor clinically or by level after starting the herb, and separate dosing by several hours since the predicted effect is on intestinal rather than hepatic glucuronidation.
CYP3A4, CYP1A2 and CYP2E1 substrates
Epimedium extract modulates hepatic CYP1A2, CYP3A4 and CYP2E1 activity, and the total flavonoid fraction has been implicated in altered sildenafil metabolism. The best-documented in vivo consequence, however, went the unexpected way: three days of Epimedium sagittatum extract significantly reduced rather than raised sildenafil AUC in rats. So the practical concern is unpredictability of exposure rather than a defined inhibition.
Clinical note: Avoid pairing this herb with narrow-index CYP3A4 substrates such as ciclosporin, tacrolimus or direct oral anticoagulants where a swing in either direction matters. If it must be used, monitor the drug rather than assuming a direction of change.
Tamoxifen, aromatase inhibitors and hormone replacement therapy
Epimedium brevicornum is described in the clinical trial literature as rich in phytoestrogen flavonoids, and the flavonoids are the basis for its use in postmenopausal bone loss. The best human evidence argues against a meaningful systemic oestrogenic effect at trial doses: in a 24-month randomised double-blind placebo-controlled trial, neither serum oestradiol nor endometrial thickness changed in either arm while bone loss was still prevented. That is reassuring but it is one trial, at one dose, with endometrial thickness as the only tissue endpoint.
Clinical note: The negative endometrial and oestradiol findings are worth quoting to a worried patient, but in a woman on adjuvant endocrine therapy for hormone-receptor-positive breast cancer the margin for an unquantified phytoestrogen is small. Prefer an alternative, and involve the oncology team if the herb is judged necessary.
Statins and other myotoxic drugs
A 33-year-old man who had taken an online Epimedium supplement for one month presented with ten hours of severe generalised muscle spasms; creatinine rose from a baseline of 1.02 to a peak of 1.44 mg/dL and creatine kinase from 1210 to a peak of 3271 U/L on day 5, normalising by day 7 after supportive care and stopping the supplement. The authors report it as the first case of severe muscle spasms with CK and creatinine elevation attributed to Epimedium. It is a single case, the product was an unanalysed internet supplement whose species and adulterant status are unknown, and no mechanism was established.
Clinical note: Weak evidence, recorded because the alternative is that a practitioner meets it with no prior. In a patient on a statin, fibrate or other myotoxic drug, ask about new muscle pain or cramp after starting the herb and check CK if present.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction | 6–10 g | Daily | — | — | 中国药典 2020 【用法与用量】6～10g。 【性味与归经】辛、甘，温。归肝、肾经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Kidney yang is warmed and the Chong and Ren regulated, strengthening yang more strongly than either alone.
Joint chief herbs of Er Xian Tang, a modern formula (Zhang Bona, 1950s) for menopausal syndrome.
Named pairing — Chen and Chen, Chinese Medical Herbology and Pharmacology
Evidence Tier
Strong evidence · 8 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
1
1 verified · 0 unverified
Randomized controlled trial
2
1 verified · 1 unverified
Show 2 studies
- Epimedium-derived flavonoids exert beneficial intervention effects on both skeletal and non-skeletal factors related to hip fracture risk in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial
- Epimedium -Derived Phytoestrogen Flavonoids Exert Beneficial Effect on Preventing Bone Loss in Late Postmenopausal Women: A 24-Month Randomized, Double-Blind and Placebo-Controlled Trial
Other clinical trial
0
Observational / case report
0
In vitro / animal
5
1 verified · 4 unverified
Show 5 studies
- Potent Inhibition of Human Phosphodiesterase-5 by Icariin Derivatives
- Drug-Drug Interactions Potential of Icariin and Its Intestinal Metabolites via Inhibition of Intestinal UDP-Glucuronosyltransferases
- Herb-Drug Interaction of Epimedium sagittatum (Sieb. et Zucc.) Maxim Extract on the Pharmacokinetics of Sildenafil in Rats
- Immunostimulatory activity and structure-activity relationship of epimedin B from Epimedium brevicornu Maxim.
- Identification of phosphodiesterase type-5 (PDE-5) inhibitors in herbal supplements using a tiered approach and associated consumer risk
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Epimedium-derived flavonoids exert beneficial intervention effects on both skeletal and non-skeletal factors related to hip fracture risk in late postmenopausal women: a 24-month randomized, double-blind and placebo-controlled trial
Report from the same 24-month randomised double-blind placebo-controlled trial of Epimedium-derived phytoestrogen flavonoids in late postmenopausal Chinese women, extending the analysis from bone mineral density to the combination of skeletal and non-skeletal determinants of hip fracture risk.
Epimedium -Derived Phytoestrogen Flavonoids Exert Beneficial Effect on Preventing Bone Loss in Late Postmenopausal Women: A 24-Month Randomized, Double-Blind and Placebo-Controlled Trial
100 healthy late postmenopausal women with a lumbar spine T-score between -2 and -2.5 were randomised to Epimedium-derived phytoestrogen flavonoids (60 mg icariin, 15 mg daidzein and 3 mg genistein daily) or placebo, both with 300 mg elemental calcium; 85 completed. Placebo lost bone at the lumbar spine (-1.7% at 12 months, -2.4% at 24 months) and femoral neck (-1.8% at 24 months) while the treated group did not, with the between-group difference significant at the lumbar spine at both time points and at the femoral neck at 24 months. Deoxypyridinoline fell 43% and 39%. Neither serum oestradiol nor endometrial thickness changed in either arm. The trial material was derived from Epimedium brevicornum, the species of this monograph, but it was a standardised flavonoid preparation containing two soy isoflavones as well as icariin, not a decoction of the crude herb.
The efficacy and safety of Epimedium in the treatment of primary osteoporosis: a systematic review and meta-analysis
10 randomised controlled trials with 890 patients (448 treated, 442 control) were pooled. Epimedium as adjunct or alternative therapy gave a higher overall efficacy rate (OR 3.80, 95% CI 2.27 to 6.37) and improved lumbar spine BMD (SMD 1.15), femoral neck BMD (SMD 1.11) and distal radius BMD (SMD 1.27), with faster relief of lower back pain. Reported adverse reactions were low and mainly mild gastrointestinal upset or skin allergy. The authors call for higher-quality studies to confirm long-term efficacy, and the pooled trials are small and largely from one region, so the effect sizes should be read as encouraging rather than settled.
Potent Inhibition of Human Phosphodiesterase-5 by Icariin Derivatives
Extracts of Tribulus terrestris, Ferula hermonis, Epimedium brevicornum and Cinnamomum cassia and the compounds cinnamaldehyde, ferutinin and icariin were screened against human recombinant PDE5A1. Only the Epimedium brevicornum extract (80% inhibition at 50 micrograms/mL) and icariin (IC50 5.9 micromolar) were active. Structural modification to 3,7-bis(2-hydroxyethyl)icaritin gave an IC50 of 75 nanomolar against sildenafil's 74 nanomolar, 80 times more potent than icariin and more selective against PDE6 and cAMP-PDE than sildenafil. This is the study that establishes both that the PDE5 mechanism of this herb is real and that icariin itself is a weak inhibitor by comparison with the licensed drugs.
Drug-Drug Interactions Potential of Icariin and Its Intestinal Metabolites via Inhibition of Intestinal UDP-Glucuronosyltransferases
Against a panel of recombinant human UGT isoforms, icariin potently inhibited UGT1A3 while its intestinal metabolites showed a different profile: icariside II inhibited UGT1A4, UGT1A7, UGT1A9 and UGT2B7, and icaritin inhibited UGT1A7 and UGT1A9. Quantitative risk prediction indicated that in vivo inhibition of intestinal UGT1A3, UGT1A4 and UGT1A7 would likely occur after oral administration of icariin-containing products.
Herb-Drug Interaction of Epimedium sagittatum (Sieb. et Zucc.) Maxim Extract on the Pharmacokinetics of Sildenafil in Rats
Rats were pretreated for three days with Epimedium sagittatum extract at 1 or 2 g/kg/day and then given intravenous sildenafil at 10 or 30 mg/kg. The AUC of sildenafil at 10 mg/kg was significantly decreased in the high-extract group, and the authors concluded that clinical co-administration of Epimedium extract and sildenafil should be prevented. The species used was Epimedium sagittatum, not Epimedium brevicornu, and the direction of the change was a fall rather than a rise in sildenafil exposure.
Immunostimulatory activity and structure-activity relationship of epimedin B from Epimedium brevicornu Maxim.
Epimedin B from Epimedium brevicornu specifically facilitated nigericin- or ATP-induced NLRP3 inflammasome activation under synergistic induction of mitochondrial reactive oxygen species, and caused caspase-1 activation and IL-1beta secretion in a lipopolysaccharide-sensitised mouse model. Pretreatment with the NLRP3 inhibitor MCC950 completely abolished inflammasome activation and prevented the liver injury. The work links the immunostimulatory activity of specific Epimedium flavonoids to the idiosyncratic liver injury reported clinically with this herb.
Identification of phosphodiesterase type-5 (PDE-5) inhibitors in herbal supplements using a tiered approach and associated consumer risk
40 herbal sexual-performance supplements were analysed by a PDE-Glo bioassay followed by LC-MS/MS. Sildenafil was found in 10 samples, tadalafil in 1 and vardenafil in 2, with total levels giving estimated daily intakes above 25 mg sildenafil equivalents and six supplements above 100 mg. Only one sample contained a natural PDE5-active constituent, icariin, at 0.013 mg/g, far too low to account for the bioassay potency, and further examination of a discordant sample identified hydroxythiohomosildenafil, an analogue absent from the reference library. The study shows that the PDE5 activity of marketed herbal products of this kind comes overwhelmingly from adulterants rather than from Epimedium constituents.
Historical Texts
Shen Nong Ben Cao Jing
Han dynastyMing Yi Bie Lu
Southern dynasties, around 500 CEBen Cao Gang Mu
Ming dynasty, 1596References
- Wang Y, Han Y, Zhu H, Xia P. A systematic review of the botany, traditional uses, phytochemistry and pharmacology of Epimedium . Phytochemistry Reviews (2024) [DOI]
- Ledo T, Patel D, Tamaska W, Espinosa J, Lucerna A. Herba Epimedium (Horny Goat Weed) Toxicity With Severe Muscle Spasms and Elevated Creatine Kinase and Creatinine: A Case Report . Cureus (2025) [DOI]
- Li C, Li Y, Bai Z, Wang J, Li G, Xiao X. Herb induced liver injury by Xianling Gubao Tablets: A case assessed for causality using updated RUCAM and integrated evidence chain . Chinese Herbal Medicines (2024) [DOI]
- Yue M, Liu Y, Feng X, Cao B, Fei X, Li G, Li C. Epimedii Folium flavonoids: A double-edged sword effect on the liver, a dual exploration of efficacy and toxicity . Journal of Pharmaceutical Analysis (2025) [DOI]
- Shi W, Li H, Liu T, Hlbiyat U, Yang J, Liu Z, Gao Y, Bai Z, Xiao X. Novel strategies for identification and prevention of idiosyncratic liver injury caused by TCM compatibility: Exemplification by Epimedii Folium and Psoraleae Fructus . Phytomedicine (2026) [DOI]
- Li HB, Chen F. Separation and Purification of Epimedin A, B, C, and Icariin from the Medicinal Herb Epimedium brevicornum Maxim by Dual-Mode HSCCC . Journal of Chromatographic Science (2009) [DOI]
- Hsueh TY, Ho JK, Lin LC, Chiu AW, Lin CH, Tsai TH. Herb–drug interaction of Epimedium extract on the pharmacokinetic of dapoxetine in rats . Journal of Chromatography B (2016) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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