MajorSSRI×Methylxanthine
Updated · Methodology
Mechanism
Fluvoxamine inhibits CYP1A2, the main clearance route of theophylline. In the study cited in the FDA label, fluvoxamine 50 mg twice daily cut theophylline clearance about 3-fold. Theophylline has a narrow therapeutic range, so a rise of this size can lead to toxicity.
Symptoms
Signs of theophylline toxicity: vomiting, agitation, pressured speech, confusion, fever, tachycardia and low blood pressure. In adults severe toxicity can cause seizures and cardiac arrest, as the theophylline SmPC describes overdose.
Management
If the combination is needed, reduce the theophylline dose to one third of the usual maintenance dose and monitor theophylline blood levels, as the FDA label states. The Spanish fluvoxamine SmPC also asks for careful monitoring and theophylline dose adjustment if needed. An antidepressant without a relevant CYP1A2 effect is sertraline: its SmPC states that it does not inhibit this enzyme to a clinically significant degree.
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Sources
- FDA: Fluvoxamine maleate tablets prescribing information (Apotex) (2026)– Apotex Corp. Fluvoxamine maleate tablets. Prescribing information, DailyMed setid 6eeb14df-6fcf-a737-5359-5744eb4accea, sections 4, 5.8 and 7.1 (Luvox brand is no longer listed)
- DailyMed: Theophylline: FDA prescribing information, Drug Interactions section (DailyMed) (2024)
- AEMPS: Ficha técnica Dumirox 100 mg (fluvoxamina) (2026)– AEMPS CIMA, Dumirox 100 mg comprimidos recubiertos con película, nº registro 58212, secciones 4.3 y 4.5
- AEMPS: Ficha técnica Theo-Dur 200 mg (teofilina) (2026)– AEMPS CIMA, Theo-Dur 200 mg comprimidos de liberación prolongada, nº registro 56165, secciones 4.3, 4.5 y 4.9