Drug Interaction Report

Colesevelam and Desogestrel: Interaction Details

A pharmacist-reviewed analysis of the Colesevelam and Desogestrel 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

Colesevelam

Welchol WelChol®
+

Desogestrel

No brand names on record
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
Major
Potentially serious — often needs a change or close 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 49 documented Colesevelam interactions, 29 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
rapid
Evidence
theoretical
Severity
Major

What happens

Decreased contraceptive effectiveness

Interaction Deep Dive

Concurrent use of an oral contraceptive containing ethinyl estradiol/norethindrone and colesevelam was associated with decreased bioavailability of the oral contraceptive. If co-treatment with colesevelam and an oral contraceptive containing ethinyl estradiol/norethindrone is necessary, patients should take the contraceptive at least 4 hours prior to colesevelam1.

Why it happens (mechanism)

Reduced absorption of contraceptive by nonspecific binding with colesevelam

Literature reports

1 report — tap to read

a) Concurrent administration of colesevelam in participants receiving an oral contraceptive containing ethinyl estradiol and norethindrone significantly reduced the exposure of the contraceptive. Coadministration of colesevelam 3.75 g with ethinyl estradiol 0.035 mg/norethindrone 1 mg resulted in reductions of 24% in both ethinyl estradiol AUC and Cmax, and a 1% and 20% reduction in norethindrone AUC and Cmax, respectively. When the combination contraceptive was administered 1 hour prior to colesevelam, the AUC and Cmax were changed by -18% and -1%, respectively, for ethinyl estradiol, and by 5% and -3%, respectively, for norethindrone. Administration of the combination contraceptive 4 hours prior to colesevelam, led to a -12% change in ethinyl estradiol AUC, and changes of 6% and 7% in norethindrone AUC and Cmax, respectively 1.

Common questions

Can I take Colesevelam and Desogestrel together?

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

How serious is the Colesevelam and Desogestrel interaction?

It is rated major. Potentially serious — often needs a change or close 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Colesevelam or Desogestrel 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 a safer alternative to one of these medications for me?

References (1)

  1. Product Information: WELCHOL oral tablets, colesevelam hcl oral tablets. Daiichi Sankyo Inc, Parsippany, NJ, 2008. DailyMed
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Colesevelam

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All Colesevelam interactions (49) Colesevelam drug information
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Desogestrel

Keep reading about Desogestrel

All Desogestrel interactions (46)
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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:

Colesevelam + Activated Charcoal Coffee Charcoal European Mandrake Glucomannan Guar Gum Gum Arabic Slippery Elm Tragacanth + 9 more
Desogestrel + Activated Charcoal Grapefruit St. John's Wort Acacia Rigidula Adrafinil African Wild Potato American Elder Astaxanthin + 132 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.