Drug & supplement interaction

Red Yeast Rice + Lapatinib

Lapatinib brand name: Tykerb.

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

Red Yeast Rice has a moderate interaction with Lapatinib. Theoretically, drugs that inhibit the CYP3A4 enzymes might increase levels of lovastatin from red yeast rice.

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

Red Yeast Rice and Lapatinib

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS

Why this applies to Lapatinib

Lapatinib falls under CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS — the group Red Yeast Rice interacts with.

Theoretically, drugs that inhibit the CYP3A4 enzymes might increase levels of lovastatin from red yeast rice.
Red yeast rice contains varying levels of the statin drug lovastatin, which is metabolized by CYP3A4. Combining red yeast rice with CYP3A4 inhibitors might increase serum levels of lovastatin from red yeast rice.
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 thing to know about this combo: lapatinib (Tykerb) blocks a liver enzyme called CYP3A4, and that same enzyme is what clears the lovastatin hiding inside red yeast rice. So in theory, taking them together could let the statin part of red yeast rice build up in your body more than it should.

When statin levels run high, the main worry is muscle problems, things like aching, weakness, or in rare cases real muscle breakdown, plus extra strain on the liver. I'll be honest, this is based on how the drugs work on paper rather than strong studies, and red yeast rice products vary a lot in strength. Still, while you're on cancer treatment, please loop in your oncologist or pharmacist before adding it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Prescribing Information. Mevacor (lovastatin). Whitehouse Station, NJ: Merck & Co., Inc., February 2012.

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

Red Yeast Rice Also Interacts With Other Medications

Red Yeast Rice has 476 moderate known drug interactions in our database — the Lapatinib one above is one of them. If you take anything else, check it against the full list below.

Moderate 476 No known interaction 2,354 (incl. Lapatinib)
Taking anything else?

Check Another of Your Medications Against Red Yeast Rice

Covers the 2,830 medications we’ve checked against Red Yeast Rice. Pick one to open its full report.

From our Q&A

Questions About Red Yeast Rice or Lapatinib

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Red Yeast Rice or Lapatinib, 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 Lapatinib

This page covers Red Yeast Rice only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Lapatinib page lists 143 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 · 100 moderate · 40 minor.

From our pharmacist’s overview on the Lapatinib page

“Of the 143 supplements on file for lapatinib (Tykerb), nearly all press on the same point, the CYP3A4 enzyme that clears this HER2-targeted breast cancer drug. That deserves real caution, since lapatinib only works when its blood level stays in range.”

Reviewed by 2 · Jul 18, 2026

Open the Lapatinib interaction page

One more smart check

Taking Red Yeast Rice as Part of a Dietary Supplement Product? Check It for Interactions

We hold 593 real supplement products containing Red Yeast Rice, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Red Yeast Rice. Your product may carry other ingredients that interact with Lapatinib too, on top of Red Yeast Rice — 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 Red Yeast Rice and Lapatinib 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 Red Yeast Rice
Top half

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

29 days ago today
Medication Lapatinib
Steady interest

#2,399 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 Red Yeast Rice

What is Red Yeast Rice?

Red Yeast Rice
  • High cholesterol
  • Heart health
  • Metabolic syndrome
  • Statin alternative

Red yeast rice contains monacolin K, which is chemically identical to the prescription statin lovastatin, and it can lower LDL ('bad') cholesterol. Because of this, it carries the same risks as statin drugs, and the amount of active ingredient varies widely between products. Always talk to your pharmacist or doctor before using it, especially if you have liver problems or take other medicines.

Read the full Red Yeast Rice monograph & all interactions
Medication

About Lapatinib

What Is Lapatinib Used For?

Brand name: Tykerb

Lapatinib tablets — sold under the brand name Tykerb — are used to treat advanced or metastatic breast cancer in patients whose tumors overexpress the HER2 protein. They are always used in combination with another medicine, not alone.

Tykerb is approved in combination with capecitabine for HER2-positive advanced or metastatic breast cancer in patients who have already received prior treatment including an anthracycline, a taxane, and trastuzumab, and whose disease has progressed on trastuzumab. Tykerb is also approved in combination with letrozole for postmenopausal women with hormone receptor-positive, HER2-positive metastatic breast cancer when hormonal therapy is appropriate.

See full Lapatinib drug information
Keep checking

Other Drugs & Red Yeast Rice

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

0Major
476Moderate
0Minor
2,353No known interaction
476 Moderate 2,353 No interaction
Moderate

476 interactions

Showing 60 of 476 moderate interactions — see all 476 on the Red Yeast Rice page.

No interaction 2,353 drugs checked — show the list

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

Showing the 60 most looked-up of 2,353 medications checked with no known interaction — see the full Red Yeast Rice list.

See the full Red Yeast Rice interactions page
See every supplement checked against Lapatinib, 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
Red Yeast Rice monograph › Uses, safety, and every drug interaction in one place Lapatinib supplement interactions › Every supplement checked against Lapatinib, ranked by severity Lapatinib 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 Red Yeast Rice and Lapatinib Together: Common Questions

Can you take Red Yeast Rice with Lapatinib?
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 Red Yeast Rice and Lapatinib 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 Lapatinib and Red Yeast Rice?

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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.