Phenobarbital and Valproic Acid: Drug Interaction Guide

Quick answer: This combination requires caution. Phenobarbital and Valproic Acid can be used together with adjustments and monitoring.

Interaction severity: Moderate — caution required

How Phenobarbital interacts with Valproic Acid

Valproate inhibits the hepatic metabolism of phenobarbital, raising phenobarbital levels and causing excessive sedation and cognitive impairment.

What you should do

Reduce phenobarbital dose by approximately one-third when starting valproate and monitor phenobarbital levels and clinical sedation.

Key facts

Severity

Moderate — caution required

Mechanism

Valproate inhibits the hepatic metabolism of phenobarbital, raising phenobarbital levels and causing excessive sedation ...

Action

Reduce phenobarbital dose by approximately one-third when starting valproate and monitor phenobarbital levels and clinic...

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 Phenobarbital and Valproic Acid together?

With caution. Reduce phenobarbital dose by approximately one-third when starting valproate and monitor phenobarbital levels and clinical sedation.

What is the severity of this interaction?

The interaction between Phenobarbital and Valproic Acid is classified as Moderate — caution required. Valproate inhibits the hepatic metabolism of phenobarbital, raising phenobarbital levels and causing excessive sedation and cognitive impairment.

What should I do if I'm prescribed both?

Reduce phenobarbital dose by approximately one-third when starting valproate and monitor phenobarbital levels and clinical sedation. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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