THE POTENTIAL FOR QT PROLONGATION ASSOCIATED WITH MACROLIDE AND QUINOLONE ANTIBIOTIC PRESCRIBING IN THE EASTERN REGION HEALTH AREA.

The General Medical Services (GMS) prescribing database was used to identify GMS antibiotic prescribing for the ERHA over the time period January to December 2003. Both JMP–In and SAS software packages were used to identify macrolide and quinolone antibiotic co-prescribing with drugs known to prolong the QT interval whose metabolism may be inhibited by these antibiotics. Approximately 96,000 prescriptions for the macrolide (erythromycin 20,400, clarithromycin 48,840 prescriptions) and quinolone (ciprofloxacin 16,200) antibiotics were issued in the ERHA during 2003. Potential for interaction with the macrolide antibiotics was noted for cisapride and tamoxifen. Forty one of the 12,900 prescriptions for tamoxifen (0.32 %) were in combination with a macrolide (erythromycin 12, clarithromycin 29 patients). Seventy of the 16,200 prescriptions for ciprofloxacin (0.43 %) were in combination with amitriptyline, haloperidol and imipramine (amitriptyline 50, imipramine 1 and haloperidol 19 patients). Recent reports highlight the increased risk of sudden death from cardiac causes associated with macrolide antibiotics, with prolongation of the QT interval as a likely mechanism. Our study highlights the potential for QT prolongation arising from pharmacokinetic interactions with macrolide and quinolone antibiotics in the community setting in Ireland.