Moderate
Amiodarone × Loratadine
Class III antiarrhythmics (Vaughan Williams)×Second-generation antihistamines
Mechanism
Loratadine causes minimal QT prolongation at standard doses, but with CYP3A4 blockade by amiodarone, loratadine levels rise, potentially amplifying cardiac effects in predisposed patients.
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
Standard loratadine 10 mg/day is kept. In patients with prior QT prolongation, hypokalaemia, or bradycardia below 60 bpm, switch to cetirizine (minimal QT effect). Check ECG every 3–6 months on the combination.
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.