Drug interactions
Olanzapine + Phenobarbital
Severity: Moderate
Olanzapine and Phenobarbital: moderate 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 hepatic enzymes and can lower olanzapine concentrations, potentially reducing efficacy. Both drugs are sedating, so excessive drowsiness and respiratory depression are also possible.
What this interaction means in plain words
Olanzapine and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Enzyme induction (including CYP1A2 and glucuronidation) lowering olanzapine exposure, plus additive CNS depression.
What to do
Monitor clinical response and sedation, and consider increasing the olanzapine dose or checking levels if efficacy falls. Reassess the dose if phenobarbital is stopped.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Olanzapine and Phenobarbital, 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 Olanzapine
Frequently asked questions
Can I take Olanzapine with Phenobarbital?
MediHelp rates the interaction as moderate. Olanzapine and Phenobarbital can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenobarbital induces hepatic enzymes and can lower olanzapine concentrations, potentially reducing efficacy. Both drugs are sedating, so excessive drowsiness and respiratory depression are also possible.
How serious is the interaction between Olanzapine and Phenobarbital?
MediHelp rates it moderate, 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 consider increasing the olanzapine dose or checking levels if efficacy falls. Reassess the dose if phenobarbital is stopped.
What other medicines interact with Olanzapine?
MediHelp also lists interactions of Olanzapine with, for example, Amisulpride, Amoxapine, Apomorphine. The full list is on the Olanzapine 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.
