QTc Interval Prolongation in Patients on Long-Term Methadone Maintenance TherapyMaremmani I. · Pacini M. · Cesaroni C. · Lovrecic M. · Perugi G. · Tagliamonte A.
aPISA-SIA (Study and Intervention on Addictions) Group ‘Santa Chiara’, University Hospital, Department of Psychiatry, NFB, University of Pisa, bInstitute of Behavioral Sciences ‘G. De Lisio’, Carrara, cAssociation for the Application of Neuroscientific Knowledge to Social Aims (AU-CNS onlus), Pietrasanta, LU, dSerT ASL 22 Novi Ligure-Ovada-Aqui Terme, and eDepartment of Neurosciences, Pharmacology Section, University of Siena, Italy; fInstitute of Health of the Republic of Slovenia, Ljubljana, Slovenia
Objective: The aim of the present study was to assess the incidence of abnormal QTc interval values in a population of subjects on a long-term methadone maintenance treatment, as a single therapy, and with methadone dosages ranging between 10 and 600 mg/daily (mean ± SD = 87 ± 76). Method: Basal ECG recordings were carried out in 83 former heroin addicts on long-term successful methadone maintenance therapy for at least 6 months, while no other known QT-prolonging agent was being administered. Results: Eighty-three percent of the subjects had a more prolonged QT interval than the reference values for persons of the same sex and age. Only 2 patients displayed a QTc interval of >500 ms. No correlation emerged between QTc values and methadone dosages. Conclusion: Patients on long-term methadone maintenance treatment show longer than expected QTc interval values. This data, associated with the finding that methadone is a rather potent inhibitor of HERG potassium channels and that it may induce torsade de pointes in predisposed subjects, supports the recommendation that patients entering methadone treatment (MT) are screened for cardiac risk factors. ECG might be considered in ongoing MT patients especially before starting QT-prolonging medications.