Phenytoin and Theophylline: Drug Interaction Guide

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

Interaction severity: Moderate — caution required

How Phenytoin interacts with Theophylline

Phenytoin induces hepatic CYP enzymes, increasing theophylline clearance. Theophylline may also affect phenytoin concentrations in some patients.

What you should do

Monitor theophylline concentrations and clinical response after starting or stopping phenytoin. Adjust doses based on levels and symptoms.

Key facts

Severity

Moderate — caution required

Mechanism

Phenytoin induces hepatic CYP enzymes, increasing theophylline clearance. Theophylline may also affect phenytoin concent...

Action

Monitor theophylline concentrations and clinical response after starting or stopping phenytoin. Adjust doses based on le...

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 Theophylline together?

With caution. Monitor theophylline concentrations and clinical response after starting or stopping phenytoin. Adjust doses based on levels and symptoms.

What is the severity of this interaction?

The interaction between Phenytoin and Theophylline is classified as Moderate — caution required. Phenytoin induces hepatic CYP enzymes, increasing theophylline clearance. Theophylline may also affect phenytoin concentrations in some patients.

What should I do if I'm prescribed both?

Monitor theophylline concentrations and clinical response after starting or stopping phenytoin. Adjust doses based on levels and symptoms. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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