Challenging declarations of abstinence by the determination of morphine in hair by radioimmunoassay.
Morphine extracted from dated hair segments and analysed by adaptation of a specific solid-phase 125I radioimmunoassay for the measurement of morphine in urine has provided long term histories of the heroin usage of individual patients. Results expressed as ng morphine/mg hair are compared with a pre-determined cut-off level of 0.3 ng morphine/mg hair, from a known drug-free population (n = 21). Morphine concentrations in hair samples from known heroin abusers are found to be above the cut-off limit (range 0.6-9.4 ng morphine/mg hair), and suggest a possible correlation between heroin intake and concentration of morphine in hair. Intra-assay relative standard deviation (RSD), at morphine levels of 9.27 and 1.12 ng morphine/mg hair are 2.4 and 5.5%, respectively, and acceptable recoveries from drug-free hair spiked with morphine are also achieved. The developed segmental hair analysis regime has been used successfully to challenge a self-declaration of heroin abstinence. Routine cumulative urine screening was unable to provide such evidence. The potential for hair drug analysis is discussed.