Drug & supplement interaction

St. John's Wort + Bendamustine

Bendamustine brand names: Treanda, Belrapzo, Vivimusta.

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

St. John's Wort has a moderate interaction with Bendamustine. St. John's wort may increase the metabolism and reduce the levels of CYP1A2 substrates.

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

St. John's Wort and Bendamustine

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

Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

Why this applies to Bendamustine

Bendamustine falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group St. John's Wort interacts with.

St. John's wort may increase the metabolism and reduce the levels of CYP1A2 substrates.
Clinical and in vitro research shows that St. John's wort induces CYP1A2, but to a lesser extent than CYP3A4.
Severity Moderate Likelihood Possible Evidence B

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 basic idea with bendamustine (Treanda, Belrapzo) and St. John's wort. Your liver uses an enzyme called CYP1A2 to help process bendamustine. St. John's wort tends to speed that enzyme up, so in theory it could clear this chemo drug a little faster and lower the amount working in your body. That could mean your treatment doesn't hit cancer cells as hard as your oncologist intended.

Honestly, the evidence here is on the softer side, and St. John's wort affects CYP1A2 less strongly than other enzymes. Still, with a cancer treatment you don't want to second-guess the dosing. Please don't add St. John's wort without first checking with your oncologist or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Henderson L, Yue QY, Bergquist C, et al. St John's wort (Hypericum perforatum): drug interactions and clinical outcomes. Br J Clin Pharmacol 2002;54:349-56..
  2. Foster BC, Vandenhoek S, Hana J, et al. In vitro inhibition of human cytochrome P450-mediated metabolism of marker substrates by natural products. Phytomedicine 2003;10:334-42.. PubMed
  3. Van Strater, A. C. and Bogers, J. P. Interaction of St John's wort (Hypericum perforatum) with clozapine. Int.Clin.Psychopharmacol. 2012;27(2):121-124. PubMed
  4. Haron MH, Dale O, Martin K, et al. Evaluation of the Herb-Drug Interaction Potential of Commonly Used Botanicals on the US Market with Regard to PXR- and AhR-Mediated Influences on CYP3A4 and CYP1A2. J Diet Suppl 2022. 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

St. John's Wort Also Interacts With Other Medications

St. John's Wort has 755 major, 387 moderate known drug interactions in our database — the Bendamustine one above is one of them. If you take anything else, check it against the full list below.

Major 755 Moderate 387 No known interaction 1,688 (incl. Bendamustine)
Taking anything else?

Check Another of Your Medications Against St. John's Wort

Covers the 2,830 medications we’ve checked against St. John's Wort. Pick one to open its full report.

From our Q&A

Questions About St. John's Wort or Bendamustine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers St. John's Wort or Bendamustine, 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 Bendamustine

This page covers St. John's Wort only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Bendamustine page lists 87 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Acerola (moderate), Adrafinil (moderate), African Wild Potato (moderate), Alpha-lipoic Acid (moderate) and Ashitaba (moderate).

By severity: 62 moderate · 25 minor.

From our pharmacist’s overview on the Bendamustine page

“Bendamustine (Treanda, Belrapzo, Vivimusta) is IV chemotherapy for chronic lymphocytic leukemia and certain lymphomas, and the liver clears it through an enzyme called CYP1A2. That enzyme is why nearly all 87 supplements on this page appear here, since about 80 of them can push CYP1A2 up or down, which could either raise side effects o…”

Reviewed by 2 · Jul 18, 2026

Open the Bendamustine interaction page

One more smart check

Taking St. John's Wort as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,159 real supplement products containing St. John's Wort, each one broken down to its full ingredient list — and combination products often carry several ingredients besides St. John's Wort. Your product may carry other ingredients that interact with Bendamustine too, on top of St. John's Wort — 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 St. John's Wort and Bendamustine 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 St. John's Wort
Top 25%

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

29 days ago today
Medication Bendamustine
Top 5%

#56 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 St. John's Wort

What is St. John's Wort?

St. John's Wort
  • Mild to moderate depression
  • Anxiety and stress
  • Sleep problems
  • Menopausal symptoms
  • Wound healing (topical)

St. John's wort is a well-studied herb most often used for mild to moderate depression, and some research suggests it may help with this. However, it has many serious interactions with prescription medicines and is not safe for everyone, so always talk to your pharmacist or doctor before taking it.

Read the full St. John's Wort monograph & all interactions
Medication

About Bendamustine Injection

What Is Bendamustine Injection Used For?

Brand names: Treanda, Belrapzo, Vivimusta

Bendamustine hydrochloride injection is used to treat adults with chronic lymphocytic leukemia (CLL). It is also used for adults with indolent B-cell non-Hodgkin lymphoma (NHL) — a slow-growing type of blood cancer — when the disease has continued to progress during or within six months of treatment with rituximab or a rituximab-containing regimen.

For CLL, how well bendamustine works compared to other first-line treatments (aside from chlorambucil) has not been fully established.

See full Bendamustine Injection drug information
Keep checking

Other Drugs & St. John's Wort

Browse every other medication we’ve checked against St. John's Wort — both the ones with a known interaction and the ones without. Select any drug for the full detail.

755Major
387Moderate
0Minor
1,687No known interaction
755 Major 387 Moderate 1,687 No interaction
Major

755 interactions

Showing 60 of 755 major interactions — see all 755 on the St. John's Wort page.

Moderate

387 interactions

Showing 60 of 387 moderate interactions — see all 387 on the St. John's Wort page.

No interaction 1,687 drugs checked — show the list

We also checked St. John's Wort against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,687 medications checked with no known interaction — see the full St. John's Wort list.

See the full St. John's Wort interactions page
See every supplement checked against Bendamustine, 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
St. John's Wort monograph › Uses, safety, and every drug interaction in one place Bendamustine supplement interactions › Every supplement checked against Bendamustine, ranked by severity Bendamustine Injection 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 St. John's Wort and Bendamustine Together: Common Questions

Can you take St. John's Wort with Bendamustine?
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 St. John's Wort and Bendamustine 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 Bendamustine and St. John's Wort?

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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.