Drug & supplement interaction

Boldo + Sulfamethoxazole, Trimethoprim

Sulfamethoxazole, Trimethoprim brand names: Bactrim, Bactrim DS, Cotrim DS, Septra, Septra DS, and others.

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

Boldo has a moderate interaction with Sulfamethoxazole, Trimethoprim. Theoretically, taking boldo with hepatotoxic drugs might increase the risk of hepatic injury and disease.

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

Boldo and Sulfamethoxazole, Trimethoprim

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Sulfamethoxazole, Trimethoprim

Sulfamethoxazole, Trimethoprim falls under HEPATOTOXIC DRUGS — the group Boldo interacts with.

Theoretically, taking boldo with hepatotoxic drugs might increase the risk of hepatic injury and disease.
Boldo leaf contains ascaridole, a known liver toxin. Many cases of hepatotoxicity, including elevated liver transaminase levels and jaundice, have been reported in patients taking boldo.
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 boldo and Bactrim (sulfamethoxazole/trimethoprim). Boldo leaf contains a compound called ascaridole that can be hard on the liver, and there are real-world reports of people developing liver irritation, raised liver enzymes, and even jaundice (yellowing of the skin or eyes) while using it. Bactrim, on its own, can also occasionally stress the liver. Stacking the two together may add up and raise the chance of liver problems.

To be fair, this is mostly theoretical and based on scattered case reports, not strong studies. Still, I'd play it safe while you're on a Bactrim course. Watch for fatigue, dark urine, belly pain, or yellowing, and check with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Piscaglia F, Leoni S, Venturi A, et al. Caution in the use of boldo in herbal laxatives: a case of hepatotoxicity. Scand J Gastroenterol 2005;40:236-9. PubMed
  2. Ribeiro RJ, Silvestre C, Duarte C. Hidden risks of alternative medicines: a case of boldo-induced hepatotoxicity. J Diet Suppl 2017;14(2):186-90. PubMed
  3. Oliveira Sá A, Pimentel T, Oliveira N. Boldo-Induced Hepatotoxicity: A Case of Unexplained Jaundice. Eur J Case Rep Intern Med 2020;7(12):002116. 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

Boldo Also Interacts With Other Medications

Boldo has 481 moderate known drug interactions in our database — the Sulfamethoxazole, Trimethoprim one above is one of them. If you take anything else, check it against the full list below.

Moderate 481 No known interaction 2,349 (incl. Sulfamethoxazole, Trimethoprim)
Taking anything else?

Check Another of Your Medications Against Boldo

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

Everything else you take

See Every Supplement That Interacts With Sulfamethoxazole, Trimethoprim

This page covers Boldo only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sulfamethoxazole, Trimethoprim page lists 174 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 139 moderate · 24 minor.

From our pharmacist’s overview on the Sulfamethoxazole, Trimethoprim page

“The supplement I check first with sulfamethoxazole and trimethoprim (Bactrim, Septra) is PABA, because it feeds bacteria the exact compound this antibiotic works by blocking and can cancel the treatment outright. It is one of 11 major-rated entries among 174 supplements and herbs on file here, a count that calls for genuine care.”

Reviewed by 2 · Jul 18, 2026

Open the Sulfamethoxazole, Trimethoprim interaction page

One more smart check

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

We hold 173 real supplement products containing Boldo, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Boldo. Your product may carry other ingredients that interact with Sulfamethoxazole, Trimethoprim too, on top of Boldo — 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 Boldo and Sulfamethoxazole, Trimethoprim 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 Boldo
Steady interest

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

29 days ago today
Medication Sulfamethoxazole, Trimethoprim
Steady interest

#1,720 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 Boldo

What is Boldo?

Boldo
  • Indigestion and bloating
  • Mild constipation
  • Liver and gallbladder support
  • Appetite stimulation
  • Urinary complaints

Boldo is a South American shrub whose leaves are traditionally used for digestive and gallbladder complaints, but good human evidence is very limited. The leaves and oil contain ascaridole, which can be toxic to the liver, so only ascaridole-free products should be used and only for short periods. Talk to your pharmacist or doctor before trying it, and avoid it during pregnancy and breastfeeding.

Read the full Boldo monograph & all interactions
Keep checking

Other Drugs & Boldo

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

0Major
481Moderate
0Minor
2,348No known interaction
481 Moderate 2,348 No interaction
Moderate

481 interactions

Showing 60 of 481 moderate interactions — see all 481 on the Boldo page.

No interaction 2,348 drugs checked — show the list

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

Showing the 60 most looked-up of 2,348 medications checked with no known interaction — see the full Boldo list.

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

Can you take Boldo with Sulfamethoxazole, Trimethoprim?
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 Boldo and Sulfamethoxazole, Trimethoprim 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 Sulfamethoxazole, Trimethoprim and Boldo?

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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.