Drug interactions
Phenobarbital + Quetiapine
Severity: Major
Phenobarbital and Quetiapine: 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 induces CYP3A4 and can markedly reduce quetiapine exposure, risking loss of effect. Both drugs are sedating, so additive CNS depression may also occur.
What this interaction means in plain words
Phenobarbital and Quetiapine 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
CYP3A4 induction by phenobarbital increases quetiapine clearance, plus additive CNS depression.
What to do
Monitor clinical response and sedation, and a higher quetiapine dose may be needed. Reduce the quetiapine dose again if phenobarbital is discontinued.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Phenobarbital and Quetiapine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Quetiapine
- Adagrasib + Quetiapine Major
- Amiodarone + Quetiapine Major
- Amisulpride + Quetiapine Major
- Amoxapine + Quetiapine Major
- Anagrelide + Quetiapine Major
- Apalutamide + Quetiapine Major
Frequently asked questions
Can I take Phenobarbital with Quetiapine?
MediHelp rates the interaction as major. Phenobarbital and Quetiapine 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 induces CYP3A4 and can markedly reduce quetiapine exposure, risking loss of effect. Both drugs are sedating, so additive CNS depression may also occur.
How serious is the interaction between Phenobarbital and Quetiapine?
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 clinical response and sedation, and a higher quetiapine dose may be needed. Reduce the quetiapine dose again if phenobarbital is discontinued.
What other medicines interact with Quetiapine?
MediHelp also lists interactions of Quetiapine with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Quetiapine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
