Methadone for pain and the risk of adverse cardiac outcomes

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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.

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