ModerateClass III antiarrhythmics (Vaughan Williams)×Methylxanthine
Updated · Methodology
Mechanism
Amiodarone inhibits CYP1A2 and CYP3A4 — the key enzymes of theophylline metabolism. Theophylline levels may rise by 30–50%, raising toxicity risk.
Symptoms
Nausea, tachycardia, tremor, insomnia, severe cases: seizures. Symptoms appear at theophylline above 20 mcg/mL.
Management
On starting amiodarone in a theophylline patient, cut theophylline by 30% and check levels at 1–2 weeks (target 10–15 mcg/mL). Bronchodilator alternative: tiotropium or another long-acting muscarinic antagonist.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Theo-24 (theophylline) prescribing information (2012)– ; DailyMed setid 7a108fa0-c230-475f-be93-6f864b98a410