Drug & supplement interaction

Kaolin + Trimethoprim

Trimethoprim brand names: Proloprim, Trimpex.

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

Kaolin has a moderate interaction with Trimethoprim. Kaolin may reduce the absorption of trimethoprim.

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

Kaolin and Trimethoprim

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

Moderate

TRIMETHOPRIM (Proloprim)

Kaolin may reduce the absorption of trimethoprim. To avoid a potential interaction, separate trimethoprim and kaolin doses by at least 3 hours.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the practical issue with these two together. Kaolin is a clay that works by soaking things up in your gut, and that includes part of your trimethoprim dose if you take them at the same time. When kaolin binds to the antibiotic, less of it gets absorbed into your bloodstream, so you may end up with lower drug levels than you need.

Why does that matter? Trimethoprim is fighting an infection (often a urinary tract infection), and you want enough of it in your system to clear those bacteria. If too little gets absorbed, the antibiotic may not work as well. The easy fix is timing: space your kaolin and trimethoprim doses by at least 3 hours apart. If you're unsure how to schedule them, just ask your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Babhair SA, Tariq M. Effect of magnesium trisilicate and kaolin-pectin on the bioavailability of trimethoprim. Res Commun Chem Pathol Pharmacol 1983;40:165-8.
  2. Electronic Code of Federal Regulations. Title 21. Part 335 - Antidiarrheal drug products for over-the-counter human use. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=335.50

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

Kaolin Also Interacts With Other Medications

Kaolin has 6 moderate known drug interactions in our database — the Trimethoprim one above is one of them. If you take anything else, check it against the full list below.

Moderate 6 No known interaction 2,824 (incl. Trimethoprim)
Taking anything else?

Check Another of Your Medications Against Kaolin

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

From our Q&A

Questions About Kaolin or Trimethoprim

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Kaolin or Trimethoprim, 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 Trimethoprim

This page covers Kaolin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Trimethoprim page lists 59 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), Cesium (major) and Ephedra (major).

By severity: 7 major · 41 moderate · 11 minor.

From our pharmacist’s overview on the Trimethoprim page

“Most prescriptions for trimethoprim are short courses for bladder infections, which makes it easy to assume nothing swallowed alongside it matters much. Seven of the 59 supplement and herbal ingredients here rate major, though, and nearly all of them involve heart rhythm: grapefruit in large amounts, ephedra, and a few others can prolo…”

Reviewed by 2 · Jul 18, 2026

Open the Trimethoprim interaction page

How much people look this up

Where Kaolin and 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 Kaolin
Steady interest

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

29 days ago today
Medication Trimethoprim
Steady interest

#1,692 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 Kaolin

What is Kaolin?

Kaolin
  • Diarrhea
  • Upset stomach and nausea
  • Skincare and facial masks
  • Soothing minor skin irritation
  • Excessive salivation (traditional)

Kaolin is a soft, white clay mineral that has long been used in antidiarrheal products and skincare because it absorbs water and binds substances in the gut. Older diarrhea products often combined it with pectin, but modern guidelines favor rehydration and other treatments, and high-quality evidence for kaolin alone is limited. It is generally considered low-risk for short-term use, but check with your pharmacist or doctor before use, especially during pregnancy or breastfeeding.

Read the full Kaolin monograph & all interactions
Medication

About Trimethoprim

What Is Trimethoprim Used For?

Brand names: Proloprim, Trimpex

Trimethoprim tablets are used to treat initial episodes of uncomplicated urinary tract infections (UTIs). They work only when the infection is caused by susceptible bacteria.

Like all antibiotics, it should be used only for infections that are proven or strongly suspected to be bacterial. This helps keep the medicine working and limits drug-resistant bacteria.

See full Trimethoprim drug information
Keep checking

Other Drugs & Kaolin

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

0Major
6Moderate
0Minor
2,823No known interaction
6 Moderate 2,823 No interaction
Moderate

6 interactions

No interaction 2,823 drugs checked — show the list

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

Showing the 60 most looked-up of 2,823 medications checked with no known interaction — see the full Kaolin list.

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

Can you take Kaolin with 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 Kaolin and 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 Trimethoprim and Kaolin?

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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.