Phenytoin and Quetiapine: Drug Interaction Guide

Quick answer: This combination requires caution. Phenytoin and Quetiapine can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Phenytoin interacts with Quetiapine

Phenytoin strongly induces CYP3A4, increasing quetiapine metabolism and lowering quetiapine concentrations. This can reduce antipsychotic efficacy.

What you should do

Avoid if possible or monitor for loss of psychiatric control. Quetiapine dose adjustment may be required, with reassessment after phenytoin is stopped.

Key facts

Severity

Moderate — caution required

Mechanism

Phenytoin strongly induces CYP3A4, increasing quetiapine metabolism and lowering quetiapine concentrations. This can red...

Action

Avoid if possible or monitor for loss of psychiatric control. Quetiapine dose adjustment may be required, with reassessm...

Important medical disclaimer: This page provides educational information about drug interactions for general reference. It is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss your specific medications with a qualified healthcare provider before starting, stopping, or changing any treatment. About our editorial team.

Frequently asked questions

Can I take Phenytoin and Quetiapine together?

With caution. Avoid if possible or monitor for loss of psychiatric control. Quetiapine dose adjustment may be required, with reassessment after phenytoin is stopped.

What is the severity of this interaction?

The interaction between Phenytoin and Quetiapine is classified as Moderate — caution required. Phenytoin strongly induces CYP3A4, increasing quetiapine metabolism and lowering quetiapine concentrations. This can reduce antipsychotic efficacy.

What should I do if I'm prescribed both?

Avoid if possible or monitor for loss of psychiatric control. Quetiapine dose adjustment may be required, with reassessment after phenytoin is stopped. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

Last reviewed: by iMedic Medical Editorial Team. Our editorial process.