Evaluation of baseline corrected QT interval and azithromycin prescriptions in an academic medical center

BACKGROUND: Azithromycin is used in the inpatient setting for a variety of conditions. In 2013, the US Food and Drug Administration released a warning regarding risk for corrected QT (QTc) prolongation and subsequent arrhythmias. Knowledge of inpatient prescribing patterns of QTc prolonging medications with respect to patient risk factors for adverse cardiovascular events can help recognize safe use in light of these new warnings. OBJECTIVE: To assess inpatient prescribing patterns, risk factors for QTc prolongation, and relationship between drug-drug interactions and cardiac monitoring in patients receiving azithromycin. DESIGN: Retrospective cohort study. PARTICIPANTS: One hundred inpatients ≥ 19 years of age were randomly selected from 1610 patient encounters between October 2012 and April 2013 who were administered at least 1 dose of azithromycin. MEASUREMENTS: Length of stay, reason for use, therapy duration, and concomitant medications were recorded. Telemetry charges and baseline electrocardiogram (ECG) prior to administration were assessed. RESULTS: Seventy-nine percent of azithromycin use was empiric. Sixty-five percent of patients received a baseline ECG prior to prescribing azithromycin, of which 60% had borderline or abnormal QTc prolongation. Seventy-six percent of patients were prescribed 2 or more QTc prolonging medications, of which there were more abnormal ECGs at baseline (P = 0.03) despite having telemetry ordered less than half of the time. CONCLUSIONS: In a cohort of hospitalized patients, azithromycin was prescribed despite risk factors for QTc prolongation and administration of interacting medications. Selection of azithromycin by providers appears to be independent from these risk factors, and education and vigilance to drug-drug interactions may be useful in limiting cardiac events with prescribing azithromycin.