Moderate
Amiodarone × Theophylline
Class III antiarrhythmics (Vaughan Williams)×Methylxanthine
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.