Evaluation of the methadone-alcohol interaction. I. Alterations of plasma concentration kinetics.

Clinical anecdotal reports have indicated a probably additive and/or synergistic response to the co-ingestion of ethyl alcohol and methadone. This study investigated the possible explanations for this observations, which may be associated with alterations of the plasma concentration dynamics of methadone and alcohol in the rat. Plasma concentrations of ethanol, methadone or both were followed over an eight hour period following substance administration. GC/FID and GC/MS were employed to quantify ethanol and methadone, respectively. The results of this study indicated that ethyl alcohol significantly increased peak methadone concentrations. Further, methadone significantly depressed late alcohol elimination.