Cimetidine and Theophylline: Drug Interaction Guide

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

Interaction severity: Moderate — caution required

How Cimetidine interacts with Theophylline

Cimetidine inhibits CYP1A2 and CYP3A4, reducing theophylline clearance by 30-40% and increasing risk of theophylline toxicity (seizures, arrhythmias).

What you should do

Avoid cimetidine in patients on theophylline; use famotidine or ranitidine as alternative H2-blockers, or reduce theophylline dose by 30% and monitor levels.

Key facts

Severity

Moderate — caution required

Mechanism

Cimetidine inhibits CYP1A2 and CYP3A4, reducing theophylline clearance by 30-40% and increasing risk of theophylline tox...

Action

Avoid cimetidine in patients on theophylline; use famotidine or ranitidine as alternative H2-blockers, or reduce theophy...

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 Cimetidine and Theophylline together?

With caution. Avoid cimetidine in patients on theophylline; use famotidine or ranitidine as alternative H2-blockers, or reduce theophylline dose by 30% and monitor levels.

What is the severity of this interaction?

The interaction between Cimetidine and Theophylline is classified as Moderate — caution required. Cimetidine inhibits CYP1A2 and CYP3A4, reducing theophylline clearance by 30-40% and increasing risk of theophylline toxicity (seizures, arrhythmias).

What should I do if I'm prescribed both?

Avoid cimetidine in patients on theophylline; use famotidine or ranitidine as alternative H2-blockers, or reduce theophylline dose by 30% and monitor levels. Always consult your prescribing clinician — do not stop or change medications without medical guidance.

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