Drug Interaction Report

Hydrochlorothiazide and Cholestyramine Resin: Interaction Details

A pharmacist-reviewed analysis of the Hydrochlorothiazide and Cholestyramine Resin interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Hydrochlorothiazide

Inzirqo
+

Cholestyramine Resin

Locholest® Locholest® Light Prevalite Prevalite® Questran Questran® Questran® Light
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 89 documented Hydrochlorothiazide interactions, 33 are rated moderate — including this one.
Onset
rapid
Evidence
probable
Severity
Moderate

What happens

Decreased hydrochlorothiazide concentration

Interaction Deep Dive

Cholestyramine has been shown to bind chlorothiazide and hydrochlorothiazide234. Single doses of cholestyramine bind the hydrochlorothiazide and reduce absorption from the gastrointestinal tract by up to 85% 5. During drug interaction studies, administration of cholestyramine 2 hours prior to hydrochlorothiazide and administration of hydrochlorothiazide 2 hours prior to cholestyramine resulted in decreased hydrochlorothiazide exposure. When administered concomitantly give hydrochlorothiazide 4 hours before or 4 to 6 hours after cholestyramine 1.

Why it happens (mechanism)

Binding of hydrochlorothiazide by cholestyramine in the gut

Literature reports

1 report — tap to read

a) Administration of cholestyramine 2 hour prior to administration of hydrochlorothiazide during drug interaction studies resulted in a 70% reduction in hydrochlorothiazide exposure. In addition, administration of hydrochlorothiazide 2 hours prior to cholestyramine administration resulted in a 35% reduction in hydrochlorothiazide exposure 1.

Common questions

Can I take Hydrochlorothiazide and Cholestyramine Resin together?

Decreased hydrochlorothiazide concentration Always confirm with your pharmacist or prescriber before making any change.

How serious is the Hydrochlorothiazide and Cholestyramine Resin interaction?

It is rated moderate. Can be significant — usually manageable with monitoring.

How quickly could this interaction happen?

The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.

How strong is the evidence for this interaction?

The evidence is graded "probable". Good supporting evidence, though not definitively proven.

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Questions for your pharmacist

  • Does my dose of Hydrochlorothiazide or Cholestyramine Resin need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there anything you'd monitor while I'm on both?

References (5)

  1. Product Information: Diovan HCT oral tablets, valsartan hydrochlorothiazide oral tablets. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2012. DailyMed
  2. Hunninghake DB, King S, & LaCroix K: The effect of cholestyramine and colestipol on the absorption of hydrochlorothiazide. Int J Clin Pharmacol Ther Toxicol 1982; 20:151-154.
  3. Lam YW & Shepherd AM: Drug interactions in hypertensive patients. Pharmacokinetic, pharmacodynamic, and genetic considerations. Clin Pharmacokinet 1990; 18:295-317. PubMed
  4. Hunninghake DB & Hibbard DM: Influence of time intervals for cholestyramine dosing on the absorption of hydrochlorothiazide. Clin Pharmacol Ther 1986; 39:329-334. DOI
  5. Product Information: Benicar HCT(TM), olmesartan medoxomil-hydrochlorothiazide. Sankyo Pharma Inc. Parsippany, NJ, 2003. DailyMed
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Hydrochlorothiazide

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All Hydrochlorothiazide interactions (89)
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Cholestyramine Resin

Keep reading about Cholestyramine Resin

All Cholestyramine Resin interactions (70) Cholestyramine Resin drug information
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Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Hydrochlorothiazide + Activated Charcoal American Hellebore American Mistletoe Asarabacca Dolomite Lithium Oleander Siberian Cocklebur + 222 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.