The effect of clarithromycin on the QT interval was studied in a group of 28 children treated for respiratory tract infections. QTc was measured before and following 24 h of treatment. A modest (average 22 ms, 95% CI 14-30 ms) but significant QTc prolongation (p<0.001) was observed, with seven cases having a QTc >440 ms during treatment (including a single case with QTc >460 ms).
Conclusion: Serial QTc measurements are necessary for early detection of children at risk for drug-induced arrhythmias.