PLASMA METHADONE CONCENTRATIONS AS AN INDICATOR OF OPIOID WITHDRAWAL SYMPTOMS AND HEROIN USE IN A METHADONE-MAINTENANCE PROGRAM

Plasma methadone concentrations and its main metabolite 2-ethylidiene- 1,5-dimethyl-3,5-diphenylpyrrolidine (EDDP) were determined in 93 pati ents under methadone maintenance treatment to assess their relationshi p with heroin use and opioid withdrawal symptoms. Neither plasma conce ntrations of methadone nor EDDP were significantly different when pati ents that used heroin in last 3 months were compared with those testin g negative for this drug (methadone, 355 +/- 217 versus 369 +/- 216 ng /ml, t = 0.29, P = NS; EDDP, 49 +/- 28 versus 54 +/- 40 ng/ml, t = 0.5 1, P = NS). No correlation between opioid withdrawal scale scores and plasma concentrations of methadone (r = 0.02, P = NS) and EDDP (r = - 0.14, P = NS) was found. Therapeutic drug monitoring during methadone maintenance seems to be useful for assessing compliance with treatment but not for predicting heroin use and subjective withdrawal symptoms. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.