Drug Interaction Report

Cimetidine and Carmustine: Interaction Details

A pharmacist-reviewed analysis of the Cimetidine and Carmustine 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

Cimetidine

Tagamet
+

Carmustine

BiCNU BiCNU® Gliadel
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 83 documented Cimetidine interactions, 48 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
unspecified
Evidence
theoretical
Severity
Major

What happens

Increased bone marrow toxicity (eg, leukopenia and neutropenia)

Interaction Deep Dive

Concomitant use of carmustine and oral cimetidine may result in greater myelotoxicity1. Cimetidine potentiates carmustine bone marrow depression and appears to delay recovery of bone marrow function 23. Consider alternative drugs to cimetidine 1.

Why it happens (mechanism)

Unknown

Literature reports

1 report — tap to read

a) Cimetidine has been reported to potentiate carmustine bone marrow depression and appears to delay recovery of bone marrow function 23

Common questions

Can I take Cimetidine and Carmustine together?

Increased bone marrow toxicity (eg, leukopenia and neutropenia) Always confirm with your pharmacist or prescriber before making any change.

How serious is the Cimetidine and Carmustine interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

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 Cimetidine or Carmustine 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 (3)

  1. Product Information: BiCNU(R) intravenous injection, carmustine intravenous injection. Heritage Pharmaceuticals Inc. (per FDA), Eatontown, NJ, 2017. DailyMed
  2. Selker RG, Moore P, & Lodolce D: Bone-marrow depression with cimetidine plus carmustine (letter). N Engl J Med 1978; 299:834. DOI
  3. Volkin RL, Shadduck RK, Winklestein A, et al: Potentation of carmustine-cranial irradiation-induced myelosuppression by cimetididne. Arch Intern Med 1982; 142:243-245.
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Cimetidine

Keep reading about Cimetidine

All Cimetidine interactions (83)
Also serious with: Colchicine Dofetilide Octreotide Injection Metformin
Carmustine

Keep reading about Carmustine

All Carmustine interactions (21) Carmustine drug information
Also serious with: Mumps Virus Vaccine, Live Bacillus Of Calmette And Guerin Vaccine, Live Measles Virus Vaccine, Live Dengue Tetravalent Vaccine, Live
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:

Cimetidine + Activated Charcoal Pu-erh Tea St. John's Wort Adrafinil African Wild Potato Banderol Beer Bitter Melon + 87 more
Carmustine + Activated Charcoal Acerola Alpha-lipoic Acid Coenzyme Q10 Coffee Charcoal European Mandrake Glucomannan Guar Gum + 16 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.