Drug & supplement interaction

Horny Goat Weed + Sofosbuvir, Velpatasvir

Sofosbuvir, Velpatasvir brand name: Epclusa.

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

Sofosbuvir, Velpatasvir falls into 2 drug categories that Horny Goat Weed can interact with; the most serious is rated moderate. Theoretically, horny goat weed might increase the effects and side effects of CYP2B6 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Horny Goat Weed and Sofosbuvir, Velpatasvir

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Horny Goat Weed interacts with whole categories of medication. Sofosbuvir, Velpatasvir falls into 2 of those categories, so it can interact with Horny Goat Weed in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2B6 (CYP2B6) SUBSTRATES

1 of 2

Why this applies to Sofosbuvir, Velpatasvir

Sofosbuvir, Velpatasvir falls under CYTOCHROME P450 2B6 (CYP2B6) SUBSTRATES — the group Horny Goat Weed interacts with.

Theoretically, horny goat weed might increase the effects and side effects of CYP2B6 substrates.
In vitro, horny goat weed leaf extract inhibits CYP2B6. 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 short version on combining horny goat weed with Epclusa (sofosbuvir and velpatasvir). In a lab dish, an extract of horny goat weed slowed down an enzyme called CYP2B6. In theory, blocking that enzyme could let a medicine it processes hang around a little longer, which might bump up its effects and side effects. With Epclusa, that could mean a slightly higher chance of things like headache, tiredness, or nausea.

But here's the important part: this is only test-tube evidence, and it has never actually been shown to happen in people. So I wouldn't lose sleep over it. Still, finishing your full hepatitis C course matters a lot, so please check with your pharmacist or doctor before adding this herb.

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.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Sofosbuvir, Velpatasvir also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

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 with Epclusa (sofosbuvir/velpatasvir) and horny goat weed. In lab dishes, this herb slows down an enzyme called CYP3A4, which helps clear velpatasvir from your body. If that happened in real life, velpatasvir could build up a bit and you might notice more of its usual side effects, like headache, tiredness, or nausea.

The important thing: this is only a test-tube finding, and it has never actually been shown in people. So I wouldn't lose sleep over it. Still, since finishing your full hepatitis C course matters so much, I'd run any new supplement past your pharmacist or doctor first before adding horny goat weed during treatment.

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 Sofosbuvir, Velpatasvir one above is among them. If you take anything else, check it against the full list below.

Moderate 962 No known interaction 1,868 (incl. Sofosbuvir, Velpatasvir)
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 Sofosbuvir, Velpatasvir

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 Sofosbuvir, Velpatasvir, 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 Sofosbuvir, Velpatasvir

This page covers Horny Goat Weed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sofosbuvir, Velpatasvir page lists 147 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 · 108 moderate · 36 minor.

From our pharmacist’s overview on the Sofosbuvir, Velpatasvir page

“Epclusa (the sofosbuvir and velpatasvir combination) is a finite course meant to cure hepatitis C, so I treat its supplement interactions with genuine seriousness, since anything that lowers the drug's level can undermine the cure itself. St.”

Reviewed by 2 · Jul 18, 2026

Open the Sofosbuvir, Velpatasvir 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 Sofosbuvir, Velpatasvir 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 Sofosbuvir, Velpatasvir 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%

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

29 days ago today
Medication Sofosbuvir, Velpatasvir
Steady interest

#2,698 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 Sofosbuvir and Velpatasvir

What Is Sofosbuvir and Velpatasvir Used For?

Brand name: Epclusa

Sofosbuvir and velpatasvir treats chronic hepatitis C virus (HCV) infection caused by genotypes 1, 2, 3, 4, 5, or 6 — covering all the major strains. It is approved for adults and children 3 years of age and older, whether or not they have cirrhosis (liver scarring).

It is used on its own in patients without cirrhosis or with compensated cirrhosis (where the liver is scarred but still functioning). In patients with decompensated cirrhosis (more advanced liver disease where the liver is no longer coping), it is used in combination with another medicine called ribavirin. Epclusa is a brand that is also available as oral pellets for younger children.

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

Can you take Horny Goat Weed with Sofosbuvir, Velpatasvir?
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.
Why are there 2 interactions listed for Horny Goat Weed and Sofosbuvir, Velpatasvir?
Sofosbuvir, Velpatasvir belongs to more than one drug category, and Horny Goat Weed interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Horny Goat Weed and Sofosbuvir, Velpatasvir 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 Sofosbuvir, Velpatasvir 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.