Drug Interaction Report

Colestipol and Tetracycline: Interaction Details

A pharmacist-reviewed analysis of the Colestipol and Tetracycline 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

Tetracycline

Achromycin V® Sumycin® Viabecline Vitastem
+

Colestipol

Colestid Colestid® Colestid® Flavored Granules Colestid® Granules
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 50 documented Colestipol interactions, 29 are rated moderate — including this one.
Onset
rapid
Evidence
probable
Severity
Moderate

What happens

Decreased tetracycline effectiveness

Interaction Deep Dive

A pharmacokinetic study indicates that concurrent administration of colestipol and tetracycline results in reduced bioavailability of tetracycline2.

Why it happens (mechanism)

Decreased absorption due to tetracycline binding by colestipol

Literature reports

1 report — tap to read

a) The absorption of tetracycline was reduced by 50 to 60% when given with colestipol 10 g 1. In a single dose crossover study, the concurrent administration of colestipol 30 grams and tetracycline 500 mg resulted in a greater than 50% decrease in tetracycline absorption 2.

Common questions

Can I take Colestipol and Tetracycline together?

Decreased tetracycline effectiveness Always confirm with your pharmacist or prescriber before making any change.

How serious is the Colestipol and Tetracycline 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 Colestipol or Tetracycline 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 (2)

  1. Brown RKBrown RK: The effect of concomitant administration of colestipol hydrochloride or cholestyramine and tetracycline hydrochloride on the bioavailability of orally administered tetracycline hydrochloride. Report on file, Upjohn Company, Kalamazoo, MI, 1975.
  2. Friedman H, Greenblatt DJ, & LeDuc BW: Impaired absorption of tetracycline by colestipol is not reversed by orange juice. J Clin Pharmacol 1989; 29:748-751. PubMed
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Tetracycline

Keep reading about Tetracycline

All Tetracycline interactions (27) Tetracycline drug information
Also serious with: Acitretin Isotretinoin Estradiol Transdermal Patch Penicillin G Benzathine Injection
Colestipol

Keep reading about Colestipol

All Colestipol interactions (50) Colestipol drug information
Also serious with: Bezafibrate Chenodiol Deferasirox Digoxin
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:

Tetracycline + Activated Charcoal Asarabacca Beer Oleander Siberian Cocklebur St. John's Wort Wine Alfalfa + 156 more
Colestipol + Activated Charcoal Coffee Charcoal European Mandrake Glucomannan Guar Gum Gum Arabic Niacin Slippery Elm + 10 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.