Drug & supplement interaction

Milk Thistle + simvastatin/ezetimibe

simvastatin/ezetimibe brand name: Vytorin.

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

simvastatin/ezetimibe falls into 4 drug categories that Milk Thistle can interact with; the most serious is rated moderate. Theoretically, milk thistle might affect the clearance of drugs that undergo glucuronidation.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions4
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Milk Thistle and simvastatin/ezetimibe

These two interact in 4 distinct ways. Each one is explained separately below.

Why Are There 4 Interactions?

Milk Thistle interacts with whole categories of medication. simvastatin/ezetimibe falls into 4 of those categories, so it can interact with Milk Thistle in 4 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

GLUCURONIDATED DRUGS

1 of 4

Why this applies to simvastatin/ezetimibe

simvastatin/ezetimibe falls under GLUCURONIDATED DRUGS — the group Milk Thistle interacts with.

Theoretically, milk thistle might affect the clearance of drugs that undergo glucuronidation.
Laboratory research shows that milk thistle constituents inhibit uridine diphosphoglucuronosyl transferase (UGT), the major phase 2 enzyme that is responsible for glucuronidation. Theoretically, this could decrease the clearance and increase levels of glucuronidated drugs. Other laboratory research suggests that a milk thistle extract of silymarin might inhibit beta-glucuronidase, although the significance of this effect is unclear.
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 Vytorin, which combines simvastatin and ezetimibe. Both ingredients rely partly on a clearing process in the body called glucuronidation, especially ezetimibe. In lab and animal studies, the silymarin compounds in milk thistle seem to slow that process down. In theory, that could let these drugs build up a bit, meaning slightly stronger effects and a higher chance of side effects like muscle aches, weakness, or, rarely, liver irritation.

I want to be honest though: this is theoretical and based only on test-tube and animal research, not real patient cases. For most people it's unlikely to cause trouble. Still, since you're on a statin, mention your milk thistle use to your pharmacist or doctor and report any new muscle pain.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Venkataramanan R, Ramachandran V, Komoroski BJ, et al. Milk thistle, a herbal supplement, decreases the activity of CYP3A4 and uridine diphosphoglucuronosyl transferase in human hepatocyte cultures. Drug Metab Dispos 2000;28:1270-3. DOI
  2. Kim DH, Jin YH, Park JB, Kobashi K. Silymarin and its components are inhibitors of beta-glucuronidase. Biol Pharm Bull 1994;17:443-5. PubMed
  3. Sridar C, Goosen TC, Kent UM, et al. Silybin inactivates cytochromes P450 3A4 and 2C9 and inhibits major hepatic glucuronosyltransferases. Drug Metab Dispos 2004;32:587-94. PubMed
Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 4

simvastatin/ezetimibe also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

It is unclear if milk thistle inhibits CYP3A4; research is conflicting.
While laboratory research shows conflicting results, pharmacokinetic research shows that taking milk thistle extract 420-1350 mg daily does not significantly affect the metabolism of the CYP3A4 substrates irinotecan, midazolam, or indinavir. However, 8 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are CYP3A4 substrates, including gefitinib, sorafenib, doxorubicin, and vincristine.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

Here's the gist with Vytorin: the simvastatin part is cleared by a liver enzyme called CYP3A4. In theory, if milk thistle slowed that enzyme down, simvastatin could build up in your blood and raise the chance of statin side effects like muscle aches, weakness, or (rarely) muscle breakdown. The ezetimibe half isn't really affected this way.

The reassuring news: the evidence here is weak. Most human studies show milk thistle doesn't meaningfully block CYP3A4, and this concern leans on lab work plus a handful of case reports with strong cancer drugs, not statins. So a real-world problem is unlikely. Still, it's worth a quick word with your pharmacist or doctor before adding milk thistle, especially if you ever notice new muscle pain.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Venkataramanan R, Ramachandran V, Komoroski BJ, et al. Milk thistle, a herbal supplement, decreases the activity of CYP3A4 and uridine diphosphoglucuronosyl transferase in human hepatocyte cultures. Drug Metab Dispos 2000;28:1270-3. DOI
  2. Piscitelli SC, Formentini E, Burstein AH, et al. Effect of milk thistle on the pharmacokinetics of indinavir in healthy volunteers. Pharmacotherapy 2002;22:551-6. PubMed
  3. Sridar C, Goosen TC, Kent UM, et al. Silybin inactivates cytochromes P450 3A4 and 2C9 and inhibits major hepatic glucuronosyltransferases. Drug Metab Dispos 2004;32:587-94. PubMed
  4. van Erp NP, Baker SD, Zhao M, et al. Effect of milk thistle (Silybum marianum) on the pharmacokinetics of irinotecan. Clin Cancer Res 2005;11:7800-6.
  5. Budzinski JW, Trudeau VL, Drouin CE, et al. Modulation of human cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) in Caco-2 cell monolayers by selected commercial-source milk thistle and goldenseal products. Can J Physiol Pharmacol 2007;85:966-78.
  6. Doehmer J, Weiss G, McGregor GP, Appel K. Assessment of a dry extract from milk thistle (Silybum marianum) for interference with human liver cytochrome-P450 activities. Toxicol In Vitro 2011;25:21-7. PubMed
  7. Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15. PubMed
  8. Kawaguchi-Suzuki M, Frye RF, Zhu HJ, et al. The effects of milk thistle (Silybum marianum) on human cytochrome P450 activity. Drug Metab Dispos. 2014;42(10):1611-6. PubMed
  9. Pochet S, Lechon AS, Lescrainier C, et al. Herb-anticancer drug interactions in real life based on VigiBase, the WHO global database. Sci Rep 2022;12(1):14178. PubMed
Minor

HMG-CoA REDUCTASE INHIBITORS ("Statins")

3 of 4

simvastatin/ezetimibe also falls under HMG-CoA REDUCTASE INHIBITORS ("Statins").

Theoretically, milk thistle might interfere with statin therapy by decreasing the activity of organic anion transporting polypeptide 1B1 (OATB1B1) and inhibiting breast cancer resistance protein (BCRP).
Preliminary evidence suggests that a milk thistle extract of silymarin can decrease the activity of the OATP1B1, which transports HMG-CoA reductase inhibitors into the liver to their site of action, and animal research shows this increases the maximum plasma concentration of pitavastatin and pravastatin. The silibinin component also inhibits BCRP, which transports statins from the liver into the bile for excretion. However, in a preliminary study in healthy males, silymarin 140 mg three times daily had no effect on the pharmacokinetics of a single 10 mg dose of rosuvastatin.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

Here's the gist for your Vytorin (which combines simvastatin and ezetimibe): in a test tube and in animals, milk thistle's silymarin compounds seem to slow down two transport proteins (OATP1B1 and BCRP) that help move statins into and out of the liver. In theory, that could let a bit more of the simvastatin part hang around in your blood, which might raise the odds of statin side effects like muscle aches, soreness, or weakness.

I want to be honest, though: this is very weak evidence, mostly lab and animal work, and a small human study with a similar statin showed no real change. So for most people this is unlikely to cause trouble. Still, since muscle issues with statins matter, just let your pharmacist or doctor know before adding milk thistle, and flag any unexplained muscle pain.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Deng JW, Shon JH, Shin HJ, et al. Effect of silymarin supplement on the pharmacokinetics of rosuvastatin. Pharm Res 2008;25:1807-14. PubMed
  2. Bechtold BJ, Lynch KD, Oyanna VO, et al. Rifampin- and Silymarin-Mediated Pharmacokinetic Interactions of Exogenous and Endogenous Substrates in a Transgenic OATP1B Mouse Model. Mol Pharm 2024;21(5):2284-2297. PubMed
Minor

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

4 of 4

simvastatin/ezetimibe also falls under ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP).

Milk thistle may inhibit one form of OATP, OATP-B1, which could reduce the bioavailability and clinical effects of OATP-B1 substrates.
In vitro research shows that milk thistle inhibits OATP-B1. Two case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are OATP substrates, including sorafenib and methotrexate. OATPs are expressed in the small intestine and liver and are responsible for the uptake of drugs and other compounds into the body. Inhibition of OATP may reduce the bioavailability of oral drugs that are substrates of OATP.
Severity Minor 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 Vytorin, which combines simvastatin and ezetimibe. Both of these rely partly on a transporter protein called OATP-B1 to get moved into your cells, including liver cells where statins do their work. Milk thistle may block this transporter a bit, which in theory could lower how much of the drug gets where it needs to go. That might make your cholesterol-lowering treatment work a little less well.

The important part: this is based only on lab and animal studies, not solid human research, and it's rated as a minor, possible interaction. So I wouldn't lose sleep over it. Still, if you take milk thistle regularly, mention it to your pharmacist or doctor so they can keep an eye on your cholesterol numbers.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pochet S, Lechon AS, Lescrainier C, et al. Herb-anticancer drug interactions in real life based on VigiBase, the WHO global database. Sci Rep 2022;12(1):14178. 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

Milk Thistle Also Interacts With Other Medications

Milk Thistle has 253 moderate, 700 minor known drug interactions in our database — the simvastatin/ezetimibe one above is among them. If you take anything else, check it against the full list below.

Moderate 253 Minor 700 No known interaction 1,877 (incl. simvastatin/ezetimibe)
Taking anything else?

Check Another of Your Medications Against Milk Thistle

Covers the 2,830 medications we’ve checked against Milk Thistle. Pick one to open its full report.

From our Q&A

Questions About Milk Thistle or simvastatin/ezetimibe

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Milk Thistle or simvastatin/ezetimibe, 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 simvastatin/ezetimibe

This page covers Milk Thistle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the simvastatin/ezetimibe page lists 184 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Apple (major), Beer (major), Grapefruit (major) and Siberian Cocklebur (major).

By severity: 8 major · 140 moderate · 36 minor.

From our pharmacist’s overview on the simvastatin/ezetimibe page

“Anyone taking simvastatin with ezetimibe (Vytorin) should treat this list with real care, since eight of its 184 entries are rated major and some involve everyday foods. Most of the list, 121 ingredients, runs through the CYP3A4 enzyme that clears simvastatin, and the traffic goes both ways.”

Reviewed by 2 · Jul 18, 2026

Open the simvastatin/ezetimibe interaction page

One more smart check

Taking Milk Thistle as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,560 real supplement products containing Milk Thistle, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Milk Thistle. Your product may carry other ingredients that interact with simvastatin/ezetimibe too, on top of Milk Thistle — 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 Milk Thistle and simvastatin/ezetimibe 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 Milk Thistle
Top 5%

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

29 days ago today
Medication simvastatin/ezetimibe
Top 25%

#457 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 Milk Thistle

What is Milk Thistle?

Milk Thistle
  • Liver health and protection
  • Hepatitis
  • Cirrhosis
  • Gallbladder problems
  • High cholesterol
  • Type 2 diabetes support

Milk thistle is a popular herbal supplement most often used for liver health, and its main active component is a group of compounds called silymarin. While it is generally well tolerated, the scientific evidence that it meaningfully improves liver disease or other conditions is mixed and far from conclusive. Talk with your pharmacist or doctor before using it, especially if you have a liver condition or take other medicines.

Read the full Milk Thistle monograph & all interactions
Keep checking

Other Drugs & Milk Thistle

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

0Major
253Moderate
700Minor
1,876No known interaction
253 Moderate 700 Minor 1,876 No interaction
Moderate

253 interactions

Showing 60 of 253 moderate interactions — see all 253 on the Milk Thistle page.

Minor

700 interactions

Showing 60 of 700 minor interactions — see all 700 on the Milk Thistle page.

No interaction 1,876 drugs checked — show the list

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

Showing the 60 most looked-up of 1,876 medications checked with no known interaction — see the full Milk Thistle list.

See the full Milk Thistle interactions page
See every supplement checked against simvastatin/ezetimibe, 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
Milk Thistle monograph › Uses, safety, and every drug interaction in one place simvastatin/ezetimibe supplement interactions › Every supplement checked against simvastatin/ezetimibe, ranked by severity 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 Milk Thistle and simvastatin/ezetimibe Together: Common Questions

Can you take Milk Thistle with simvastatin/ezetimibe?
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 4 interactions listed for Milk Thistle and simvastatin/ezetimibe?
simvastatin/ezetimibe belongs to more than one drug category, and Milk Thistle 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 Milk Thistle and simvastatin/ezetimibe 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 simvastatin/ezetimibe and Milk Thistle?

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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.