Methimazole and Bupropion: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Methimazole
Bupropion
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.
What happens
An increased risk of hepatotoxicity
Interaction Deep Dive
Clinicians should be aware of the possibility of acute liver insult induced by buPROPion given concurrently with other hepatotoxic drugs, such as carbimazole1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) A case has been reported of fatal liver failure possibly associated with concurrent use of buPROPion and carbimazole. A 41-year-old Chinese male was being treated with carbimazole and propranolol for 5 years. A 10-day course of buPROPion was prescribed for smoking cessation. Ten weeks after completing the course of buPROPion therapy he presented to the hospital with severe jaundice, nausea, dyspepsia, lethargy, and epigastric discomfort lasting for 5 days. His carbimazole and propranolol were discontinued. His liver enzymes were all increased (total bilirubin 29 mg/dL or 496 mcmol/L), alkaline phosphatase 138 U/L, alanine aminotransferase 674 U/L, and aspartate aminotransferase 429 U/L. He was transferred to the liver transplant unit 10 days post admission because of deterioration of renal function. Upon arrival he had grade I encephalophathy with ascites. His liver enzymes continued to increase. He was diagnosed with disseminated intravascular coagulation. A liver biopsy was suggestive of drug-induced hepatic cholestasis. The patient's status continued to decline and on day 13 he developed coagulopathy with massive intraabdominal, rectal, and oral bleeding. The patient died on day 14 due to fulminant liver failure complicated by coagulopathy, pulmonary hemorrhage, and pulmonary edema. The exact mechanism of drug-induced liver toxicity in the presence of a possible drug interaction cannot be confirmed. It is essential, however, to recognize this serious adverse effect in patients receiving concurrent treatment with carbimazole and buPROPion 1.
Common questions
Can I take Methimazole and Bupropion together?
An increased risk of hepatotoxicity Always confirm with your pharmacist or prescriber before making any change.
How serious is the Methimazole and Bupropion interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Methimazole or Bupropion 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)
- Ai-Leng K, Lai-San T, Kang-Hoe L, et al: Acute liver failure with concurrent bupropion and carbimazole therapy. Ann Pharmacother 2003; 37:220-223. PubMed
Keep reading about Methimazole
Keep reading about Bupropion
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:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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