QTc interval prolongation in patients on long-term methadone maintenance therapy.
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).


METHODS
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.


CONCLUSIONS
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.
Maremmani
Icro
I
PISA-SIA (Study and Intervention on Addictions) Group Santa Chiara, University Hospital, Department of Psychiatry, NFB, University of Pisa, Italy. maremman@psico.med.unipi.it
Pacini
Matteo
M
Cesaroni
Claudio
C
Lovrecic
Mercedes
M
Perugi
Giulio
G
Tagliamonte
Alessandro
A
D000328:Adult; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006556:Heroin Dependence / Q000534:rehabilitation*; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced* / Q000175:diagnosis; D008134:Long-Term Care; D008297:Male; D008691:Methadone / Q000009:adverse effects* / Q000627:therapeutic use; D009294:Narcotics / Q000009:adverse effects* / Q000627:therapeutic use; D012016:Reference Values; D012737:Sex Factors
D009294:Narcotics; D008691:Methadone