Drug interactions
Erythromycin + Theophylline
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.
Overview
Erythromycin can increase theophylline serum concentrations, raising risk of dose-related toxicity (e.g., nausea, vomiting, tremor, insomnia, tachyarrhythmias, seizures). Effect usually appears within 48–72 hours and is variable but can be clinically significant.
Mechanism of action
Pharmacokinetic: Erythromycin inhibits hepatic CYP3A4 (and may reduce overall hepatic clearance), decreasing theophylline metabolism; magnitude varies among patients.
Clinical management
Prefer an alternative antibiotic without this interaction when feasible. If used together, obtain baseline theophylline level, recheck level 48–72 hours after starting erythromycin, and adjust theophylline dose as needed (often dose reduction may be required). Monitor for toxicity signs/symptoms and consider ECG monitoring in high-risk patients. After erythromycin is discontinued, recheck theophylline level within 48–72 hours and retitrate to prior dose as appropriate.
Drug reference
References
- Theophylline: Drug information — UpToDate
- Theophylline (systemic): Drug Interactions — Lexicomp
- Theophylline Prescribing Information (FDA Label) – Drug Interactions — FDA Label
- Erythromycin Prescribing Information (FDA Label) – Drug Interactions — FDA Label
Frequently asked questions
Can I take Erythromycin with Theophylline?
The interaction is rated: Major. Erythromycin can increase theophylline serum concentrations, raising risk of dose-related toxicity (e.g., nausea, vomiting, tremor, insomnia, tachyarrhythmias, seizures). Effect usually appears within 48–72 hours and is variable but can be clinically significant.
How serious is the interaction between Erythromycin and Theophylline?
The interaction is rated: Major. Evidence level: High.
How is the interaction between Erythromycin and Theophylline managed?
Prefer an alternative antibiotic without this interaction when feasible. If used together, obtain baseline theophylline level, recheck level 48–72 hours after starting erythromycin, and adjust theophylline dose as needed (often dose reduction may be required). Monitor for toxicity signs/symptoms and consider ECG monitoring in high-risk patients. After erythromycin is discontinued, recheck theophylline level within 48–72 hours and retitrate to prior dose as appropriate.
Why do Erythromycin and Theophylline interact?
Pharmacokinetic: Erythromycin inhibits hepatic CYP3A4 (and may reduce overall hepatic clearance), decreasing theophylline metabolism; magnitude varies among patients.
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