Methadone for pain and the risk of adverse cardiac outcomes

Abstract

Context: There are few studies that describe cardiac adverse events in patients prescribed methadone for pain management.

Objectives: To describe incident cardiac adverse events and risk factors for cardiac adverse events in primary care patients prescribed methadone for pain.

Methods: This was a retrospective, descriptive, cohort study in patients 18 years or older receiving methadone for pain management during 2010. Patients were followed for 12 months and were categorized as "chronic" or "non-chronic" methadone users. The primary outcomes were a cardiac event, at risk for an event, or neither. Patients were grouped on their outcome and were compared on risk factors and methadone monitoring.

Results: A total of 1246 patients were included. Thirty (2.4%), 628 (50.4%), and 588 (47.2%) patients had a cardiac event, were at risk for an event, or had neither an event nor a risk factor, respectively. Overall, the rate of QTc prolongation was 49.4% and the rate of adherence to recommended cardiac monitoring was 39.0%. Similar percentages of chronic and non-chronic users had a cardiac event (P > 0.05). Among the patients who had a cardiac event and were at risk for an event, factors independently associated with having had an event included age (odds ratio = 1.06; 95% CI = 1.03-1.09) and a dose 100 mg/day or higher (odds ratio = 6.18; 95% CI = 1.08-35.45).

Conclusion: Few cardiac adverse events resulting from methadone use for pain were detected. However, a large proportion of patients were at risk for an adverse event, especially patients who were older and had received ≥ 100 mg/day of methadone.

Keywords: Methadone; analgesic-opioid/adverse effects; electrocardiography; long QT syndrome; pain management; primary health care.

Copyright © 2014 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.