Drug interactions
Amitriptyline + Phenobarbital
Severity: Major
Amitriptyline and Phenobarbital: 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
Phenobarbital is a strong enzyme inducer and can reduce amitriptyline exposure, potentially compromising its effect. Both agents are sedating, and tricyclics can also lower the seizure threshold, which may complicate seizure control.
What this interaction means in plain words
Amitriptyline and Phenobarbital 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
Induction of CYP3A4, CYP2C19, and possibly P-glycoprotein by phenobarbital, plus additive CNS depression.
What to do
Monitor for reduced antidepressant response, excessive sedation, and seizure frequency. Adjust amitriptyline dose by response or serum levels and reassess if phenobarbital is changed or stopped.
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 Amitriptyline
- Amitriptyline + Isocarboxazid Contraindicated
- Amitriptyline + Methylene blue Contraindicated
- Amitriptyline + Phenelzine Contraindicated
- Amitriptyline + Pimozide Contraindicated
- Amitriptyline + Procarbazine Contraindicated
- Amitriptyline + Safinamide Contraindicated
Frequently asked questions
Can I take Amitriptyline with Phenobarbital?
MediHelp rates the interaction as major. Amitriptyline and Phenobarbital 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. Phenobarbital is a strong enzyme inducer and can reduce amitriptyline exposure, potentially compromising its effect. Both agents are sedating, and tricyclics can also lower the seizure threshold, which may complicate seizure control.
How serious is the interaction between Amitriptyline and Phenobarbital?
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 for reduced antidepressant response, excessive sedation, and seizure frequency. Adjust amitriptyline dose by response or serum levels and reassess if phenobarbital is changed or stopped.
What other medicines interact with Amitriptyline?
MediHelp also lists interactions of Amitriptyline with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Amitriptyline page.
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