No conflict of interest was declared.
QT prolongation and torsades de pointes among methadone users: reports to the FDA spontaneous reporting system†
Article first published online: 25 MAY 2005
Copyright © 2005 John Wiley & Sons, Ltd.
Pharmacoepidemiology and Drug Safety
Volume 14, Issue 11, pages 747–753, November 2005
How to Cite
Pearson, E. C. and Woosley, R. L. (2005), QT prolongation and torsades de pointes among methadone users: reports to the FDA spontaneous reporting system. Pharmacoepidem. Drug Safe., 14: 747–753. doi: 10.1002/pds.1112
- Issue published online: 24 OCT 2005
- Article first published online: 25 MAY 2005
- Manuscript Accepted: 21 MAR 2005
- Manuscript Revised: 18 MAR 2005
- Manuscript Received: 5 OCT 2004
- US Agency for Healthcare Research and Quality to the Arizona Center for Education and Research on Therapeutics. Grant Number: U18 HS10385
- torsades de pointes;
- QT prolongation;
- adverse events
Recent case series have associated the synthetic opioid, methadone, with QT prolongation and torsades de pointes (TdP) ventricular arrhythmia.
To review and analyze adverse events (QT prolongation and TdP) reported to the Food and Drug Administration (FDA) to determine the patient characteristics, dosages of methadone, and outcomes of methadone-treated patients.
The study design was a retrieval and retrospective analysis of reports of adverse events associated with methadone voluntarily reported to the FDA MedWatch program from 1969 to October 2002. Reports were accessed via QSCAN® (DrugLogic, Reston, VA), a commercially available software interface.
In a total of 5503 reports of adverse events associated with methadone, 43 (0.78%) noted the occurrence of TdP and 16 (0.29%) QT prolongation. Doses were reported in 42/59 (71%) of cases; mean dose was 410 ± 349 mg/day (median 345, range 29–1680). The dosages for 10 of the 42 cases (29%) were within the recommended range for methadone maintenance treatment, 60–100 mg/day. Female gender, interacting medications, hypokalemia, hypomagnesemia, and structural heart disease, risk factors previously identified with other drugs known to cause TdP, were found in 44 (75%) cases. Most adverse events required hospitalization or resulted in prolonged hospitalization (28/59, 47%) and 5/59 (8%) were fatal.
Cases of TdP associated with methadone have been reported to the FDA MedWatch system. Analysis of the cases provides evidence that prolonged QT and TdP can occur over a wide range of dosages including those usually recommended for addiction treatment. Copyright © 2005 John Wiley & Sons, Ltd.