Drug & supplement interaction

Chaparral + Peginterferon alfa-2b

Peginterferon alfa-2b brand names: Peg-Intron, ViraferonPeg.

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

Chaparral has a moderate interaction with Peginterferon alfa-2b. 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 Peginterferon alfa-2b

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Peginterferon alfa-2b

Peginterferon alfa-2b 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 simple version: chaparral has been tied to serious, sometimes lasting liver damage, and that's the real worry here. Peginterferon alfa-2b is a treatment for chronic hepatitis C, and it already puts stress on the liver. Doctors watch your liver enzymes closely while you're on it. Stacking chaparral on top could, in theory, add to that liver strain.

This isn't about chaparral changing how the drug is broken down. It's about two things being hard on the same organ at the same time. The evidence here is mostly anecdotal, so the risk is theoretical, but given chaparral's track record I'd steer clear of it. Please check with your doctor or pharmacist before adding any supplement during your hepatitis C treatment.

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 Peginterferon alfa-2b 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. Peginterferon alfa-2b)
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 Peginterferon alfa-2b

This page covers Chaparral only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Peginterferon alfa-2b page lists 38 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), Ashwagandha (moderate) and Black Cohosh (moderate).

By severity: 3 major · 35 moderate.

From our pharmacist’s overview on the Peginterferon alfa-2b page

“Someone taking peginterferon alfa-2b (Peg-Intron) is usually treating hepatitis C, so the liver is already the organ under strain, and all 38 supplement interactions on file for this drug pile additional liver stress on top of it. That earns genuine caution.”

Reviewed by 2 · Jul 18, 2026

Open the Peginterferon alfa-2b 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 Peginterferon alfa-2b 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 Peginterferon alfa-2b 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

#1,048 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Peginterferon alfa-2b
Steady interest

#2,484 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 Peginterferon Alfa-2b (PEG-Intron)

What Is Peginterferon Alfa-2b (PEG-Intron) Used For?

Brand names: Peg-Intron, ViraferonPeg

  • Peginterferon alfa-2b is used alone or in combination with ribavirin (a medication) to treat chronic (long-term) hepatitis C infection (swelling of the liver caused by a virus) in people who show signs of liver damage and who have not been treated with interferon alpha (medication similar to peginterferon alfa-2b) in the past. Peginterferon alfa-2b is in a class of medications called interferons. Peginterferon alfa-2b is a combination of interferon and polyethylene glycol, which helps the interferon stay active in your body for a longer period of time. Peginterferon alpha-2b works by decreasing the amount of hepatitis C virus (HCV) in the body. Peginterferon alfa-2b may not cure hepatitis C or prevent you from developing complications of hepatitis C such as cirrhosis (scarring) of the liver, liver failure, or liver cancer. Peginterferon alfa-2b may not prevent the spread of hepatitis C to other people.

See full Peginterferon Alfa-2b (PEG-Intron) 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 Peginterferon alfa-2b, 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 Peginterferon alfa-2b supplement interactions › Every supplement checked against Peginterferon alfa-2b, ranked by severity Peginterferon Alfa-2b (PEG-Intron) 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 Peginterferon alfa-2b Together: Common Questions

Can you take Chaparral with Peginterferon alfa-2b?
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 Peginterferon alfa-2b 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 Peginterferon alfa-2b 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.