Drug interactions
Carbamazepine + Methimazole
Severity: Major
Carbamazepine and Methimazole: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Both drugs can cause bone marrow suppression, including agranulocytosis, so using them together may raise the chance of serious neutropenia. Fever or sore throat may signal a life-threatening infection.
What this interaction means in plain words
Carbamazepine and Methimazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Carbamazepine belongs to Central Nervous System; Methimazole belongs to Endocrine.
Why it happens
Additive pharmacodynamic myelotoxicity; each drug independently carries a risk of idiosyncratic agranulocytosis.
What to do
Obtain a baseline and periodic white cell count with differential, and instruct the patient to report fever or sore throat promptly. Stop the thionamide or carbamazepine if neutropenia develops, and consider an alternative anticonvulsant where feasible.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Carbamazepine
- Artemether / lumefantrine + Carbamazepine Contraindicated
- Cabotegravir + Carbamazepine Contraindicated
- Carbamazepine + Delamanid Contraindicated
- Carbamazepine + Dienogest / estradiol valerate Contraindicated
- Carbamazepine + Doravirine Contraindicated
- Carbamazepine + Elbasvir / grazoprevir Contraindicated
Other interactions of Methimazole
- Clozapine + Methimazole Major
- Methimazole + Propylthiouracil Major
- Methimazole + Sodium iodide i-131 Major
- Iodinated glycerol + Methimazole Moderate
- Iodine + Methimazole Moderate
- Lycopus + Methimazole Moderate
Frequently asked questions
Can I take Carbamazepine with Methimazole?
MediHelp rates the interaction as major. Carbamazepine and Methimazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both drugs can cause bone marrow suppression, including agranulocytosis, so using them together may raise the chance of serious neutropenia. Fever or sore throat may signal a life-threatening infection.
How serious is the interaction between Carbamazepine and Methimazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Obtain a baseline and periodic white cell count with differential, and instruct the patient to report fever or sore throat promptly. Stop the thionamide or carbamazepine if neutropenia develops, and consider an alternative anticonvulsant where feasible.
What other medicines interact with Carbamazepine?
MediHelp also lists interactions of Carbamazepine with, for example, Artemether / lumefantrine, Cabotegravir, Delamanid. The full list is on the Carbamazepine page.
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