Drug & supplement interaction

Chaparral + Interferon Beta-1a

Interferon Beta-1a brand names: Rebif, Avonex.

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

Chaparral has a moderate interaction with Interferon Beta-1a. Theoretically, chaparral might have additive adverse effects on the liver when used with hepatotoxic drugs.

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

Chaparral and Interferon Beta-1a

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Interferon Beta-1a

Interferon Beta-1a falls under HEPATOTOXIC DRUGS — the group Chaparral interacts with.

Theoretically, chaparral might have additive adverse effects on the liver when used with hepatotoxic drugs.
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 concern with combining chaparral and your interferon beta-1a (Rebif or Avonex). This isn't about chaparral changing how your MS medicine works. Instead, it's about two things that can both be hard on the liver stacking up together. Interferon beta-1a can sometimes raise liver enzymes or cause liver irritation on its own, which is why your doctor checks bloodwork. Chaparral has been tied to serious liver injury, so adding it could pile on more stress to that same organ.

To be fair, this is a theoretical, anecdotal worry, not something proven in studies. Still, given chaparral's bad track record, I'd steer clear of it. Watch for yellowing skin or eyes, dark urine, belly pain, or unusual tiredness, and please run any supplement by your doctor or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Smith BC, Desmond PV. Acute hepatitis induced by ingestion of the herbal medication chaparral. Aust N Z J Med 1993;23:526.. PubMed
  2. Gordon DW, Rosenthal G, Hart J, et al. Chaparral ingestion: the broadening spectrum of liver injury caused by herbal medications. JAMA 1995;273:489-90.
  3. Batchelor WB, Heathcote J, Wanless IR. Chaparral-induced hepatic injury. Am J Gastroenterol 1995;90:831-3.
  4. Katz M, Saibil F. Herbal hepatitis: subacute hepatic necrosis secondary to chaparral leaf. J Clin Gastroenterol 1990;12:203-6.
  5. Sheikh NM, Philen RM, Love LA. Chaparral-associated hepatotoxicity. Arch Intern Med 1997;157:913-9. DOI
  6. Chaparral-induced toxic hepatitis-California and Texas, 1992. MMWR Morb Mortal Wkly Rep 1992;41:812-4.. DOI
  7. Estes JD, Stolpman D, Olyaei A, et al. High prevalence of potentially hepatotoxic herbal supplement use in patients with fulminant hepatic failure. Arch Surg 2003;138:852-8.. 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

Chaparral Also Interacts With Other Medications

Chaparral has 369 moderate known drug interactions in our database — the Interferon Beta-1a one above is one of them. If you take anything else, check it against the full list below.

Moderate 369 No known interaction 2,461 (incl. Interferon Beta-1a)
Taking anything else?

Check Another of Your Medications Against Chaparral

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

Everything else you take

See Every Supplement That Interacts With Interferon Beta-1a

This page covers Chaparral only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Interferon Beta-1a page lists 57 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Beer (major), Siberian Cocklebur (major), Wine (major), Alfalfa (moderate) and Angelica Archangelica (moderate).

By severity: 3 major · 53 moderate · 1 minor.

From our pharmacist’s overview on the Interferon Beta-1a page

“Siberian cocklebur, an herb tied to documented cases of liver failure, is the first name to know for anyone injecting interferon beta-1a (Rebif, Avonex) for multiple sclerosis. Interferon beta-1a can strain the liver on its own, which is why prescribers order routine liver blood tests, and 38 of the 57 supplements on file carry that sa…”

Reviewed by 2 · Jul 18, 2026

Open the Interferon Beta-1a interaction page

One more smart check

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

We hold 83 real supplement products containing Chaparral, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Chaparral. Your product may carry other ingredients that interact with Interferon Beta-1a too, on top of Chaparral — 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 Chaparral and Interferon Beta-1a 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 Chaparral
Steady interest

#1,014 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Interferon Beta-1a
Top half

#1,104 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 Chaparral

What is Chaparral?

Chaparral
  • Pain and inflammation
  • Skin conditions
  • Antioxidant/general wellness
  • Infections
  • Traditional 'detox' remedies

Chaparral is a desert shrub long used in traditional medicine, but there is no reliable proof it treats any condition. It has been linked to serious and sometimes irreversible liver and kidney damage, and the FDA has warned against using it. Because of these safety concerns, we recommend avoiding chaparral.

Read the full Chaparral monograph & all interactions
Medication

About Interferon Beta-1a Intramuscular Injection

What Is Interferon Beta-1a Intramuscular Injection Used For?

Brand names: Rebif, Avonex

  • Interferon beta-1a intramuscular injection is used to treat adults with various forms of multiple sclerosis (MS; a disease in which the nerves do not function properly and people may experience weakness, numbness, loss of muscle coordination, and problems with vision, speech, and bladder control) including:

    • clinically isolated syndrome (CIS; nerve symptom episodes that last at least 24 hours),

    • relapsing-remitting forms (course of disease where symptoms flare up from time to time), or

    • secondary progressive forms (course of disease where relapses occur more often).

  • Interferon beta-1a is in a class of medications called immunomodulators. It works by decreasing inflammation and preventing nerve damage that may cause symptoms of multiple sclerosis.

See full Interferon Beta-1a Intramuscular Injection drug information
Keep checking

Other Drugs & Chaparral

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

0Major
369Moderate
0Minor
2,460No known interaction
369 Moderate 2,460 No interaction
Moderate

369 interactions

Showing 60 of 369 moderate interactions — see all 369 on the Chaparral page.

No interaction 2,460 drugs checked — show the list

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

Showing the 60 most looked-up of 2,460 medications checked with no known interaction — see the full Chaparral list.

See the full Chaparral interactions page
See every supplement checked against Interferon Beta-1a, 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
Chaparral monograph › Uses, safety, and every drug interaction in one place Interferon Beta-1a supplement interactions › Every supplement checked against Interferon Beta-1a, ranked by severity Interferon Beta-1a Intramuscular 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 Chaparral and Interferon Beta-1a Together: Common Questions

Can you take Chaparral with Interferon Beta-1a?
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 Chaparral and Interferon Beta-1a 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 Interferon Beta-1a and Chaparral?

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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.