Moderate
Amiodarone × fluvoxamine
Class III antiarrhythmics (Vaughan Williams)×SSRI
Mechanism
Fluvoxamine is a strong CYP1A2 inhibitor and moderate CYP3A4 inhibitor. Levels of amiodarone and its active metabolite (desethylamiodarone) can rise, amplifying the QT effect.
Symptoms
QT prolongation on ECG. Dizziness, syncope, palpitations. Rarely: polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Avoid the combination. In depression and anxiety on amiodarone, alternatives: sertraline or escitalopram (the latter cautiously in older patients, cap at 10 mg). If unavoidable, start fluvoxamine at 25 mg/day and check ECG at 1 and 2 weeks.
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.