Drug & supplement interaction

Comfrey + Zanubrutinib

Zanubrutinib brand name: Brukinsa.

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

Comfrey has a moderate interaction with Zanubrutinib. Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid constituents in comfrey.

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

Comfrey and Zanubrutinib

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) INDUCERS

Why this applies to Zanubrutinib

Zanubrutinib falls under CYTOCHROME P450 3A4 (CYP3A4) INDUCERS — the group Comfrey interacts with.

Theoretically, CYP3A4 inducers might increase the risk of adverse effects from the pyrrolizidine alkaloid constituents in comfrey.
CYP3A4 enzymes convert pyrrolizidine alkaloids, constituents of comfrey, to toxic metabolites. Some case reports show that enzyme inducers, such as phenobarbital, seem to enhance the toxicity of comfrey.
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 twist with this pairing: the worry isn't about your cancer medicine getting too strong or too weak. It actually runs the other way. Comfrey contains compounds called pyrrolizidine alkaloids that the liver enzyme CYP3A4 turns into toxic byproducts. Zanubrutinib is a mild inducer of that same enzyme, meaning it can speed it up a bit. In theory, a faster enzyme could create more of comfrey's harmful liver products, raising the risk of liver damage.

I want to be honest that this is a theoretical concern based on how these things work in the lab, not a proven event with zanubrutinib. Still, comfrey is hard on the liver on its own and should never be swallowed. Since liver health matters a lot during cancer treatment, please run any comfrey use, even skin products, past your oncologist or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Stickel F, Seitz HK. The efficacy and safety of comfrey. Public Health Nutr 2000;3:501-8. PubMed
  2. Chojkier M. Hepatic sinusoidal-obstruction syndrome: toxicity of pyrrolizidine alkaloids. J Hepatol 2003;39:437-46. PubMed
  3. Wang YP, Yan J, Fu PP, Chou MW. Human liver microsomal reduction of pyrrolizidine alkaloid N-oxides to form the corresponding carcinogenic parent alkaloid. Toxicol Lett 2005;155:411-20. 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

Comfrey Also Interacts With Other Medications

Comfrey has 437 moderate known drug interactions in our database — the Zanubrutinib one above is one of them. If you take anything else, check it against the full list below.

Moderate 437 No known interaction 2,393 (incl. Zanubrutinib)
Taking anything else?

Check Another of Your Medications Against Comfrey

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

Everything else you take

See Every Supplement That Interacts With Zanubrutinib

This page covers Comfrey only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zanubrutinib page lists 160 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 · 119 moderate · 38 minor.

From our pharmacist’s overview on the Zanubrutinib page

“Grapefruit is the biggest supplement risk with zanubrutinib (Brukinsa), a targeted therapy for certain blood cancers, and this list deserves genuine care. Grapefruit blocks the enzyme (CYP3A4) that clears the drug, so levels can climb and side effects with them.”

Reviewed by 2 · Jul 18, 2026

Open the Zanubrutinib interaction page

One more smart check

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

We hold 29 real supplement products containing Comfrey, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Comfrey. Your product may carry other ingredients that interact with Zanubrutinib too, on top of Comfrey — 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 Comfrey and Zanubrutinib 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 Comfrey
Steady interest

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

29 days ago today
Medication Zanubrutinib
Top 25%

#498 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 Comfrey

What is Comfrey?

Comfrey
  • Bruises and sprains
  • Muscle and joint pain
  • Minor wounds and skin irritation
  • Back pain
  • Inflammation

Comfrey is a traditional herb used mainly on the skin for bruises, sprains, and joint pain, and some topical products show modest benefit for these uses. However, comfrey contains compounds that can seriously damage the liver, so it should never be taken by mouth and should only be used on unbroken skin for short periods. Pregnant or breastfeeding people should avoid it entirely.

Read the full Comfrey monograph & all interactions
Medication

About Zanubrutinib

What Is Zanubrutinib Used For?

Brand name: Brukinsa

Brukinsa (zanubrutinib) is used to treat adult patients with certain blood cancers. It treats mantle cell lymphoma (MCL) in patients who have had at least one prior therapy, Waldenström's macroglobulinemia (WM), relapsed or refractory marginal zone lymphoma (MZL) after at least one prior anti-CD20 treatment, and chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).

Brukinsa is also used — in combination with another medicine called obinutuzumab — to treat relapsed or refractory follicular lymphoma (FL) in adults who have already received two or more lines of treatment. Several of these uses were granted accelerated FDA approval based on response rates, meaning confirmatory trials are still ongoing.

See full Zanubrutinib drug information
Keep checking

Other Drugs & Comfrey

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

0Major
437Moderate
0Minor
2,392No known interaction
437 Moderate 2,392 No interaction
Moderate

437 interactions

Showing 60 of 437 moderate interactions — see all 437 on the Comfrey page.

No interaction 2,392 drugs checked — show the list

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

Showing the 60 most looked-up of 2,392 medications checked with no known interaction — see the full Comfrey list.

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

Can you take Comfrey with Zanubrutinib?
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 Comfrey and Zanubrutinib 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 Zanubrutinib and Comfrey?

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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.