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Theophylline-mexiletine interaction: a case report.
J D Kendall1, M M Chrymko, B E Cooper
1Pharmacy Service, Department of Veterans Affairs Medical Center, Erie, PA 16504.
Pharmacotherapy
|January 1, 1992
Summary
Theophylline toxicity can occur in patients with chronic obstructive pulmonary disease (COPD) when starting mexiletine due to drug interactions. Stopping mexiletine improved theophylline clearance, resolving toxicity.
Area of Science:
- Pharmacology
- Clinical Medicine
- Drug Interactions
Background:
- Theophylline and mexiletine are medications used in managing chronic obstructive pulmonary disease (COPD) and cardiac arrhythmias.
- Both drugs share common metabolic pathways, raising concerns about potential drug-drug interactions.
Observation:
- A patient with COPD and arrhythmias, already on theophylline, developed theophylline toxicity shortly after initiating mexiletine therapy.
- Clinical monitoring revealed a significant increase in theophylline levels during concurrent mexiletine use.
Findings:
- The co-administration of theophylline and mexiletine resulted in a clinically significant drug interaction.
- Discontinuation of mexiletine led to a marked improvement in theophylline clearance and resolution of toxicity symptoms.
Implications:
- Clinicians should exercise caution when prescribing theophylline and mexiletine concurrently, especially in patients with COPD.
- Awareness of shared metabolic pathways is crucial for predicting and preventing adverse drug events.
- Therapeutic drug monitoring and dose adjustments may be necessary to manage this interaction safely.