QT INTERVAL PROLONGATION AND TORSADES-DE-POINTES DUE TO ERYTHROMYCIN LACTOBIONATE

Study Objectives. To discern the frequency of torsades de pointes and QT prolongation in patients receiving intravenous erythromycin lactobi onate; to examine the degree of QT prolongation and QT dispersion due to intravenous erythromycin in a typical clinical setting; and to iden tify any concurrent factors that might predispose patients to excessiv e QT prolongation or torsades de pointes while receiving intravenous e rythromycin. Design. Retrospective cohort trial. Setting. A university teaching hospital. Patients. All inpatients who received intravenous erythromycin lactobionate during a 1-year period. Measurements and Mai n Results. The records of 278 consecutive patients were analyzed, of w hom 49 had 12-lead electrocardiograms while receiving and not receivin g erythromycin. The dosages of erythromycin ranged from 18-83 (42 +/- 18) mg/kg/day. Of the 49 patients, the baseline QTc was 432 +/- 39 mse c, compared with 483 +/- 62 msec during erythromycin therapy (p<0.01). In 30 of 49 patients with heart disease, the increase in QTc due to e rythromycin was 15 +/- 11%, compared with 8.6 +/- 10% in the 19 patien ts without heart disease (p<0.05). The degree of QTc dispersion was 34 +/- 16 msec at baseline, compared with 80 +/- 35 msec with erythromyc in (p<0.01). Overall, 19 (39%) of 49 patients had a moderate to severe delay in ventricular repolarization (QTc greater than or equal to 500 msec). Of the 278 patients prescribed intravenous erythromycin over t he year, it caused torsades de pointes in just one (less than or equal to 0.4%). Conclusion. Erythromycin lactobionate-induced torsades de p ointes is rare, although QT prolongation is common. Some patients may be at risk for suffering torsades de pointes due to this agent, partic ularly if heart disease or other factors that may further delay ventri cular repolarization are present.