Prospective Study of QTc Changes Among Former Opiate Addicts Since Admission to Methadone Maintenance Treatment

Abstract

To prospectively evaluate QTc changes among methadone maintenance treatment (MMT) patients. All 512 opiate addicts newly admitted to 2 MMT clinics had been prospectively studied for 4.5 years. Ninety-one patients were excluded because they were admitted from other MMTs, and 26 were excluded because their first electrocardiogram was performed following 28 days in MMT; therefore, 421 were studied. QTc values were again performed either after (A) a steady methadone dose for at least 3 months and negative urine tests for opiates, cocaine, amphetamines, cannabis, benzodiazepine; or after (B) same as for (A) but with positive urine tests for cannabis and/or benzodiazepine. Mean QTc intervals were not related to benzodiazepine or cocaine use on admission. QTc interval was significantly prolonged from the baseline to steady methadone dose (424.5 ± 23.2 ms and 438.6 ± 26.6 ms, respectively) but not affected by methadone dose (<100 or ≥100 mg/d) or by the time to achieve a steady methadone dose (between 3 months and >2 years). QTc prolongation was greater among patients whose urine tested positive for benzodiazepine on a steady dose (P = 0.003). No additional prolongation was observed in 49 patients who achieved a steady methadone dose less than 1 year in MMT and had additional follow-up. Two patients who were benzodiazepine abusers died for undefined reasons. There is significant QTc prolongation during early MMT with no apparent clinical significance. A combination of benzodiazepine and methadone should be monitored.