Major
Amiodarone × Metronidazole
Class III antiarrhythmics (Vaughan Williams)×Imidazole derivatives (antiprotozoal / antibacterial)
Mechanism
Metronidazole prolongs the QT interval. Combined with amiodarone, torsades de pointes has been reported, especially with hypokalaemia.
Symptoms
QT prolongation on ECG. Dizziness, syncope, palpitations. Severe cases: polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia and hypomagnesaemia.
Management
Avoid the combination. Alternative antibiotics without QT effect: a cephalosporin, amoxicillin-clavulanate, or fosfomycin. For anaerobic infection requiring metronidazole: ECG before start and at day 2.
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.