Drug interactions
Carbamazepine + Phenindione
Severity: Major
Carbamazepine and Phenindione: major interaction.
Last updated Sources: UK SmPC
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
Carbamazepine can reduce the anticoagulant effect of phenindione, raising the risk of thrombosis. When carbamazepine is withdrawn, anticoagulation may become excessive.
What this interaction means in plain words
Carbamazepine and Phenindione 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.
Why it happens
Carbamazepine induces hepatic enzymes, increasing metabolism of phenindione.
What to do
Monitor INR closely when starting or stopping carbamazepine and adjust the phenindione dose. Consider an alternative anticoagulant.
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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References
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
Frequently asked questions
Can I take Carbamazepine with Phenindione?
MediHelp rates the interaction as major. Carbamazepine and Phenindione 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 can reduce the anticoagulant effect of phenindione, raising the risk of thrombosis. When carbamazepine is withdrawn, anticoagulation may become excessive.
How serious is the interaction between Carbamazepine and Phenindione?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor INR closely when starting or stopping carbamazepine and adjust the phenindione dose. Consider an alternative anticoagulant.
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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