Drug interactions
Carbamazepine + Fentanyl
Severity: Major
Carbamazepine and Fentanyl: major interaction.
Last updated Sources: US FDA label
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 is a strong CYP3A4 inducer and can substantially lower fentanyl exposure, leading to loss of analgesia or withdrawal in dependent patients. Stopping carbamazepine later can cause fentanyl levels to rise and cause toxicity.
What this interaction means in plain words
Carbamazepine and Fentanyl 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; Fentanyl belongs to Musculoskeletal.
Why it happens
Induction of CYP3A4-mediated fentanyl metabolism by carbamazepine.
What to do
Monitor pain control and withdrawal symptoms and increase the fentanyl dose as needed. When carbamazepine is stopped or reduced, lower the fentanyl dose and monitor for respiratory depression.
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 Fentanyl
- Alvimopan + Fentanyl Contraindicated
- Fentanyl + Isocarboxazid Contraindicated
- Fentanyl + Olanzapine / samidorphan Contraindicated
- Fentanyl + Phenelzine Contraindicated
- Fentanyl + Tranylcypromine Contraindicated
- Alfentanil + Fentanyl Major
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 Fentanyl?
MediHelp rates the interaction as major. Carbamazepine and Fentanyl 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 is a strong CYP3A4 inducer and can substantially lower fentanyl exposure, leading to loss of analgesia or withdrawal in dependent patients. Stopping carbamazepine later can cause fentanyl levels to rise and cause toxicity.
How serious is the interaction between Carbamazepine and Fentanyl?
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 pain control and withdrawal symptoms and increase the fentanyl dose as needed. When carbamazepine is stopped or reduced, lower the fentanyl dose and monitor for respiratory depression.
What other medicines interact with Fentanyl?
MediHelp also lists interactions of Fentanyl with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Fentanyl page.
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