Drug interactions
Mexiletine + Theophylline
Severity: Major
Mexiletine and Theophylline: major interaction.
Last updated Sources: US FDA label
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
Mexiletine markedly reduces theophylline clearance, with documented rises in serum theophylline concentrations and toxicity such as nausea, tachyarrhythmias and seizures.
What this interaction means in plain words
Mexiletine and Theophylline can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Mexiletine belongs to Cardiovascular; Theophylline belongs to Respiratory.
Why it happens
Mexiletine inhibits CYP1A2, the main enzyme metabolizing theophylline.
What to do
Reduce the theophylline dose when starting mexiletine and monitor serum levels closely. Recheck levels after stopping mexiletine.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
- Theophylline (Anhydrous) - FDA drug label (DailyMed) — openFDA / DailyMed
Other interactions of Theophylline
- Riociguat + Theophylline Contraindicated
- Adenosine + Theophylline Major
- Apalutamide + Theophylline Major
- Bupropion + Theophylline Major
- Carvedilol + Theophylline Major
- Cimetidine + Theophylline Major
Other interactions of Mexiletine
- Fezolinetant + Mexiletine Contraindicated
- Mexiletine + Pimozide Contraindicated
- Alosetron + Mexiletine Major
- Amiodarone + Mexiletine Major
- Clozapine + Mexiletine Major
- Cobicistat + Mexiletine Major
Frequently asked questions
Can I take Mexiletine with Theophylline?
MediHelp rates the interaction as major. Mexiletine and Theophylline can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Mexiletine markedly reduces theophylline clearance, with documented rises in serum theophylline concentrations and toxicity such as nausea, tachyarrhythmias and seizures.
How serious is the interaction between Mexiletine and Theophylline?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reduce the theophylline dose when starting mexiletine and monitor serum levels closely. Recheck levels after stopping mexiletine.
What other medicines interact with Theophylline?
MediHelp also lists interactions of Theophylline with, for example, Riociguat, Adenosine, Apalutamide. The full list is on the Theophylline page.
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