Diazepam and methadone blood levels following concurrent administration of diazepam and methadone.
Results of a previous study indicated that the opioid effects of methadone were enhanced by the concurrent administration of diazepam in methadone-maintained subjects. To determine whether a pharmacokinetic interaction might account for this methadone-diazepam interaction, the plasma levels of methadone, diazepam and diazepam metabolites were determined in blood samples collected during that study. Five adult male patients on methadone maintenance (50-60 mg/day) were administrated single doses of placebo, diazepam (20 and 40 mg), methadone (100%, 150% and 200% of the maintenance dose), and four diazepam-methadone dose combinations (20 and 40 mg diazepam in combination with 100% and 150% of the maintenance dose). The results showed that the concurrent administration of methadone and diazepam did not significantly change the time-course or areas under the plasma concentration-time curve of methadone, diazepam or N-desmethyl-diazepam compared to the levels following the administration of either drug alone. Thus, plasma drug level analysis does not indicate a pharmacokinetic interaction between diazepam and methadone.
D000328:Adult; D002855:Chromatography, Thin Layer; D003975:Diazepam / Q000008:administration & dosage / Q000097:blood*; D004347:Drug Interactions; D006801:Humans; D007124:Immunoenzyme Techniques; D007700:Kinetics; D008297:Male; D008540:Meiosis / Q000187:drug effects; D008691:Methadone / Q000008:administration & dosage / Q000097:blood*; D003708:Nordazepam / Q000097:blood
D003708:Nordazepam; D003975:Diazepam; D008691:Methadone