Drug & supplement interaction

Horny Goat Weed + Aprepitant

Aprepitant brand names: Emend, Cinvanti.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Horny Goat Weed has a moderate interaction with Aprepitant. Theoretically, horny goat weed might increase the effects and side effects of CYP3A4 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Horny Goat Weed and Aprepitant

Here is the interaction we found between these two, with the evidence behind it.

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Aprepitant

Aprepitant falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Horny Goat Weed interacts with.

Theoretically, horny goat weed might increase the effects and side effects of CYP3A4 substrates.
In vitro, horny goat weed extract inhibits CYP3A4 and suppresses CYP3A4 mRNA expression. This effect has not been reported in humans.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for Emend (aprepitant). Your body clears this medicine using a liver enzyme called CYP3A4. In test-tube studies, horny goat weed appears to slow that same enzyme down. If that happened in people, aprepitant could build up a bit more than usual, which might mean stronger effects and a higher chance of side effects like tiredness, hiccups, headache, or constipation.

The big caveat: this is only seen in lab studies, not in actual humans, so it's a theoretical concern rather than something proven. Still, since you're taking aprepitant during chemotherapy, this isn't the time to add an unstudied herb on your own. Please run it by your oncology pharmacist or doctor first so they can weigh in for your situation.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Li K, Yu XH, Maskey AR, et al. Cytochrome P450 3A4 suppression by epimedium and active compound kaempferol leads to synergistic anti-inflammatory effect with corticosteroid. Front Pharmacol 2023;13:1042756. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Horny Goat Weed Also Interacts With Other Medications

Horny Goat Weed has 962 moderate known drug interactions in our database — the Aprepitant one above is one of them. If you take anything else, check it against the full list below.

Moderate 962 No known interaction 1,868 (incl. Aprepitant)
Taking anything else?

Check Another of Your Medications Against Horny Goat Weed

Covers the 2,830 medications we’ve checked against Horny Goat Weed. Pick one to open its full report.

From our Q&A

Questions About Horny Goat Weed or Aprepitant

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Horny Goat Weed or Aprepitant, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Aprepitant

This page covers Horny Goat Weed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Aprepitant page lists 158 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Adrafinil (moderate).

By severity: 3 major · 116 moderate · 39 minor.

From our pharmacist’s overview on the Aprepitant page

“Aprepitant (Emend, Cinvanti) keeps chemotherapy patients from vomiting, so a supplement that undoes it mid-cycle is a problem, and I read this list with genuine vigilance. Nearly all 158 entries touch CYP3A4, the liver enzyme that clears aprepitant.”

Reviewed by 2 · Jul 18, 2026

Open the Aprepitant interaction page

One more smart check

Taking Horny Goat Weed as Part of a Dietary Supplement Product? Check It for Interactions

We hold 183 real supplement products containing Horny Goat Weed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Horny Goat Weed. Your product may carry other ingredients that interact with Aprepitant too, on top of Horny Goat Weed — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Horny Goat Weed and Aprepitant Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Horny Goat Weed
Top 25%

#297 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Aprepitant
Top 25%

#450 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Horny Goat Weed

What is Horny Goat Weed?

Horny Goat Weed
  • Erectile dysfunction
  • Low libido
  • Fatigue and low energy
  • Bone health
  • Joint and menopausal symptoms
  • General 'vitality' or performance

Horny goat weed (Epimedium) is a traditional Chinese herb most often marketed for low libido and erectile problems, but solid human evidence for these uses is lacking. While short-term use seems generally tolerated by some people, quality and safety are not well studied, so talk to your pharmacist or doctor before trying it—especially if you have heart problems or take other medicines.

Read the full Horny Goat Weed monograph & all interactions
Medication

About Aprepitant

What Is Aprepitant Used For?

Brand names: Emend, Cinvanti

Aprepitant is used to prevent nausea and vomiting — not to treat it once it has started. It is always used alongside other anti-nausea medicines, not on its own.

EMEND capsules (oral) are approved for adults and children 12 and older to prevent nausea from highly or moderately emetogenic (nausea-causing) chemotherapy. EMEND for oral suspension extends that same use down to children as young as 6 months. CINVANTI (IV injection) is approved for adults only, for chemotherapy-related nausea. APONVIE (IV emulsion) is approved for adults to prevent postoperative nausea and vomiting (PONV) — nausea after surgery. Aprepitant capsules (generic) are approved for adults and children 12 and older for chemotherapy-related nausea, and also for adults to prevent PONV.

See full Aprepitant drug information
Keep checking

Other Drugs & Horny Goat Weed

Browse every other medication we’ve checked against Horny Goat Weed — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
962Moderate
0Minor
1,867No known interaction
962 Moderate 1,867 No interaction
Moderate

962 interactions

Showing 60 of 962 moderate interactions — see all 962 on the Horny Goat Weed page.

No interaction 1,867 drugs checked — show the list

We also checked Horny Goat Weed against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,867 medications checked with no known interaction — see the full Horny Goat Weed list.

See the full Horny Goat Weed interactions page
See every supplement checked against Aprepitant, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Horny Goat Weed monograph › Uses, safety, and every drug interaction in one place Aprepitant supplement interactions › Every supplement checked against Aprepitant, ranked by severity Aprepitant drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Horny Goat Weed and Aprepitant Together: Common Questions

Can you take Horny Goat Weed with Aprepitant?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Horny Goat Weed and Aprepitant interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Aprepitant and Horny Goat Weed?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.