Drug & supplement interaction

Cat's Claw + Rituximab

Rituximab brand name: Rituxan.

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

Cat's Claw has a moderate interaction with Rituximab. Theoretically, cat's claw might interfere with immunosuppressive therapy.

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

Cat's Claw and Rituximab

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

Moderate

IMMUNOSUPPRESSANTS

Why this applies to Rituximab

Rituximab falls under IMMUNOSUPPRESSANTS — the group Cat's Claw interacts with.

Theoretically, cat's claw might interfere with immunosuppressive therapy.
In human and laboratory research, cat's claw has been shown to have immunostimulating activity. It stimulates phagocytosis and increases respiratory cellular activity and the mobility of leukocytes. Theoretically, this could interfere with the activity of immunosuppressant medications.
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 thinking behind pairing cat's claw with Rituximab (Rituxan). Rituximab works by quieting down part of your immune system, which is exactly what you want whether you're treating lymphoma, leukemia, or rheumatoid arthritis. Cat's claw, on the other hand, seems to do the opposite in lab and animal studies. It appears to stir up immune cells, boosting things like white blood cell activity. So the worry is that the supplement could work against what Rituximab is trying to accomplish, possibly making it less effective.

I want to be honest about how soft this evidence is. This is theoretical, based mostly on test-tube and animal research, not real patients on Rituximab. Still, since this is serious therapy, I'd run it by your oncologist, rheumatologist, or pharmacist before starting cat's claw rather than guessing.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Sandoval M, Charbonnet RM, Okuhama NN, et al. Cat's claw inhibits TNFalpha production and scavenges free radicals: role in cytoprotection. Free Radic Biol Med 2000;29:71-78.
  2. Sheng, Y., Bryngelsson, C., and Pero, R. W. Enhanced DNA repair, immune function and reduced toxicity of C-MED-100, a novel aqueous extract from Uncaria tomentosa. J Ethnopharmacol. 2000;69(2):115-126. PubMed
  3. Lamm, S., Sheng, Y., and Pero, R. W. Persistent response to pneumococcal vaccine in individuals supplemented with a novel water soluble extract of Uncaria tomentosa, C-Med-100. Phytomedicine 2001;8(4):267-274.
  4. Sheng, Y., Li, L., Holmgren, K., and Pero, R. W. DNA repair enhancement of aqueous extracts of Uncaria tomentosa in a human volunteer study. Phytomedicine 2001;8(4):275-282.

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

Cat's Claw Also Interacts With Other Medications

Cat's Claw has 961 moderate known drug interactions in our database — the Rituximab one above is one of them. If you take anything else, check it against the full list below.

Moderate 961 No known interaction 1,869 (incl. Rituximab)
Taking anything else?

Check Another of Your Medications Against Cat's Claw

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

From our Q&A

Questions About Cat's Claw or Rituximab

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Cat's Claw or Rituximab, 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 Rituximab

This page covers Cat's Claw only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Rituximab page lists 53 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Active Hexose Correlated Compound (ahcc) (moderate), Alfalfa (moderate), American Ginseng (moderate), Andrographis (moderate) and Ashwagandha (moderate).

By severity: 52 moderate · 1 minor.

From our pharmacist’s overview on the Rituximab page

“Rituximab (Rituxan) works by knocking down part of the immune system, clearing out the B cells that drive lymphomas, leukemias, and autoimmune diseases like rheumatoid arthritis. All 53 supplements here interact the same way, showing some evidence of stimulating immune activity that could in theory blunt what the drug is trying to do.”

Reviewed by 2 · Jul 18, 2026

Open the Rituximab interaction page

One more smart check

Taking Cat's Claw as Part of a Dietary Supplement Product? Check It for Interactions

We hold 910 real supplement products containing Cat's Claw, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cat's Claw. Your product may carry other ingredients that interact with Rituximab too, on top of Cat's Claw — 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 Cat's Claw and Rituximab 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 Cat's Claw
Top 25%

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

29 days ago today
Medication Rituximab
Top 25%

#366 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 Cat's Claw

What is Cat's Claw?

Cat's Claw
  • Osteoarthritis and rheumatoid arthritis
  • Inflammation
  • Immune support
  • Digestive complaints
  • General wellness/tonic

Cat's claw is a South American vine traditionally used for inflammation, joint pain, and immune support. Some small studies hint it may help with arthritis symptoms, but the overall evidence is limited and not strong enough to confirm clear benefits. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Cat's Claw monograph & all interactions
Medication

About Rituximab Injection

What Is Rituximab Injection Used For?

Brand name: Rituxan

Rituximab is used to treat a range of blood cancers and immune-driven diseases. In cancer care, it targets certain types of Non-Hodgkin's Lymphoma (NHL) and Chronic Lymphocytic Leukemia (CLL) — both in adults and, for some lymphomas, in children as young as 6 months old.

Beyond cancer, rituximab is also approved for moderately-to-severely active Rheumatoid Arthritis (RA) in adults who haven't responded well to other treatments, as well as for two rare inflammatory blood vessel diseases — Granulomatosis with Polyangiitis (GPA) and Microscopic Polyangiitis (MPA) — and for a serious skin blistering condition called Pemphigus Vulgaris (PV).

See full Rituximab Injection drug information
Keep checking

Other Drugs & Cat's Claw

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

0Major
961Moderate
0Minor
1,868No known interaction
961 Moderate 1,868 No interaction
Moderate

961 interactions

Showing 60 of 961 moderate interactions — see all 961 on the Cat's Claw page.

No interaction 1,868 drugs checked — show the list

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

Showing the 60 most looked-up of 1,868 medications checked with no known interaction — see the full Cat's Claw list.

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

Can you take Cat's Claw with Rituximab?
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 Cat's Claw and Rituximab 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 Rituximab and Cat's Claw?

Our pharmacists answer your medication & supplement questions — free.

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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.