Moderate
Amiodarone × Linezolid
Class III antiarrhythmics (Vaughan Williams)×Oxazolidinone antibiotic
Mechanism
Linezolid mildly prolongs QT, additively with amiodarone. Clinically significant arrhythmia is rare, but risk is higher with hypokalaemia, hypomagnesaemia, and bradycardia.
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
For short linezolid courses (10–14 days), check ECG before start and one week in. Keep potassium and magnesium in the upper half of the normal range. In atrial fibrillation with prior ventricular arrhythmia, alternatives: vancomycin or daptomycin.