RADIOIMMUNOASSAY OF DRUGS OF ABUSE IN HAIR .2. THE DETERMINATION OF METHADONE IN THE HAIR OF KNOWN DRUG-USERS

This communication addresses the analytical problems associated with t he analysis of hair specimens from known users and misusers of the syn thetic opioid methadone. An adapted radioimmunoassay and a previously developed preanalytical decontamination procedure have been applied to samples from known drug users. The removal of drugs from the hair sur face by washing and the effect of proprietary hair treatments on metha done entrapped in the hair have also been investigated. Pre-analytical washing reduced methadone levels by up to 29%, whilst hair colouratio n and peroxide bleaching were found to reduce levels by up to 21% and 50% respectively. Methadone assay of extracts from dated hair segments were shown to provide long term histories of methadone intake, under controlled and non-controlled conditions. Evidence that a dose relatio nship between hair drug levels and intake may exist is presented. Resu lts of hair analysis, expressed as ng methadone/mg hair, from drug use rs (range 0.20-10.63) are compared to a pre-determined cut-off of 0.1 ng methadone/mg hair, obtained from the analysis of a known drug free population (n = 23).