Effects of concomitant amiodarone and haloperidol on Q-Tc interval prolongation.

Purpose: The effects of concomitant amiodarone and haloperidol on Q-Tc interval prolongation were studied.

Methods: All adult patients admitted to a 618-bed tertiary referral teaching hospital between January 1, 2005, and December 31, 2006, who received amiodarone and haloperidol concomitantly were included in this retrospective descriptive analysis. Data collected to assess patients' risk of developing Q-T interval prolongation included age, sex, past medical history, and number of days of concomitant exposure. Data relevant for the assessment of cardiac effects were collected for the time period between 24 hours before and after the administration of haloperidol and included laboratory test values, use of other Q-T interval-prolonging drugs, heart rate, Q-Tc intervals, and clinical documentation of arrhythmia. To determine change in the Q-Tc interval, Q-T and R-R values were recorded using cardiac rhythm strips or electrocardiogram. Nurses' and physicians' records were reviewed to determine if an arrhythmia occurred. Descriptive statistics were used to analyze baseline patient information and Q-Tc interval data.

Results: A total of 49 patients met inclusion criteria, yielding 381 distinct amiodarone-haloperidol exposures. During 138 (36.2%) of 381 haloperidol-amiodarone exposures, patients received at least one additional Q-T interval-prolonging drug. When amiodarone-haloperidol exposures were grouped by the number of concomitant Q-T prolonging drugs, no apparent association was detected between longer Q-Tc intervals and an increased number of concomitant Q-T interval-prolonging drugs.

Conclusion: A small, potentially significant Q-Tc interval prolongation, but not ventricular arrhythmia, was observed in adult patients who received a concomitant administration of amiodarone and haloperidol at a tertiary referral teaching hospital.