Drug & supplement interaction

Horny Goat Weed + Pirfenidone

Pirfenidone brand name: Esbriet.

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

Horny Goat Weed has a moderate interaction with Pirfenidone. Theoretically, horny goat weed might increase the effects and side effects of CYP1A2 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 Pirfenidone

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

Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

Why this applies to Pirfenidone

Pirfenidone falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group Horny Goat Weed interacts with.

Theoretically, horny goat weed might increase the effects and side effects of CYP1A2 substrates.
In vitro, horny goat weed leaf extract inhibits CYP1A2. 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 Esbriet (pirfenidone). Your body clears this medicine largely through a liver enzyme called CYP1A2. In test-tube studies, horny goat weed appears to slow that same enzyme down. If it did the same thing in people, your pirfenidone could be cleared a little slower and build up, which may mean more of its usual side effects, things like nausea, stomach upset, tiredness, dizziness, loss of appetite, or increased sun sensitivity and skin rash.

I want to be honest about the evidence, though: this is only seen in lab dishes, not in actual patients, so it's theoretical. Pirfenidone is not a prodrug, so more drug around means stronger effects, not weaker. Before combining them, just run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zhong Q, Shi Z, Zhang L, et al. The potential of Epimedium koreanum Nakai for herb-drug interaction. J Pharm Pharmacol 2017;69(10):1398-408. doi: 10.1111/jphp.12773.

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 Pirfenidone 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. Pirfenidone)
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 Pirfenidone

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 Pirfenidone, 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 Pirfenidone

This page covers Horny Goat Weed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Pirfenidone page lists 115 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Adrafinil (moderate), African Wild Potato (moderate), Alfalfa (moderate) and Angelica Archangelica (moderate).

By severity: 1 major · 80 moderate · 34 minor.

From our pharmacist’s overview on the Pirfenidone page

“Pirfenidone (Esbriet) slows the lung scarring of idiopathic pulmonary fibrosis, and when a drug is doing that kind of work, this is not a list to skim. Most of the 115 ingredients on file touch CYP1A2, the liver enzyme that clears pirfenidone, so they can push its blood level up (more nausea and liver strain) or drag it down and quietl…”

Reviewed by 2 · Jul 18, 2026

Open the Pirfenidone 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 Pirfenidone 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 Pirfenidone 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%

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

29 days ago today
Medication Pirfenidone
Top 25%

#611 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 Pirfenidone

What Is Pirfenidone Used For?

Brand name: Esbriet

Pirfenidone — available as capsules and tablets under the brand name Esbriet, as well as generic pirfenidone products — is indicated for the treatment of idiopathic pulmonary fibrosis (IPF), a chronic, progressive disease in which scar tissue builds up in the lungs and makes breathing increasingly difficult.

Esbriet capsules and tablets, pirfenidone capsules, and pirfenidone tablets are each specifically approved for IPF. No other uses are supported by the available product labels.

See full Pirfenidone 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 Pirfenidone, 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 Pirfenidone supplement interactions › Every supplement checked against Pirfenidone, ranked by severity Pirfenidone 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 Pirfenidone Together: Common Questions

Can you take Horny Goat Weed with Pirfenidone?
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 Pirfenidone 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 Pirfenidone 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.