Interpretation of hair findings in children after methadone poisoning

Methadone is not licensed for use in children though it can be employed for the management of neonatal opiate withdrawal syndrome. During the last 2 years, our laboratory has been asked to test for methadone and EDDP, its major metabolite, in hair from children that were admitted to hospital unconscious and where methadone had already been identified in a body fluid (4 cases) or where the children were deceased and evidence of methadone overdosage having already been established (2 cases). In all of these cases, segmental analysis revealed approximately the same amount of drug along the hair lock. As a consequence, contamination was considered as an issue and interpretation of the results was a challenge that deserves particular attention. After decontamination with dichloromethane and segmentation the hair was cut into small pieces, incubated overnight at 40 degrees C, liquid-liquid extracted and analysed with LC-MS/MS, using 2 transitions per compound. The LOQ for both methadone and EDDP was 10 pg/mg. In the first series involving children admitted to hospital, the following results were obtained: * case 1: 4 x 1 cm section, methadone at 0.05-0.08 ng/mg, no EDDP detected, * case 2: 4 x 1 cm section, methadone at 0.13-0.15 ng/mg, EDDP at 0.02 ng/mg, * case 3: 3 x 1.5 cm section, methadone at 0.07-0.09 ng/mg, EDDP at 0.01-0.03 ng/mg, * case 4: 6 x 2 cm section, methadone at 0.06-0.13 ng/mg, EDDP at 0.02-0.03 ng/mg. The following concentrations were obtained from the children who had died following a methadone overdose: * case 5: 2 x 2 cm section, methadone at 0.53-0.58 ng/mg, no EDDP detected, * case 6: 4 x 1 cm section, methadone at 0.44-0.77 ng/mg, EDDP at 0.04-0.06 ng/mg. The first observation is that all these concentrations are low by comparison with those observed in adults on methadone maintenance therapy. However, the more surprising observation is the relative homogenous concentrations along the hair locks in each specific case. This raises concerns around the possibility that contamination could have occurred prior to sampling and makes it hard to reach a conclusion regarding the possibility of repeated methadone exposure in the months prior the incidents. In these cases it was impossible to conclude that the children were deliberately administered methadone. The results of the analysis of hair could indicate that they were in an environment where methadone was being used and where the drug was not being handled and stored with appropriate care. The homogenous concentrations found on segmental analyses could be indicative of external contamination that may have arisen not only from direct contamination with the drug but also via contamination with body fluids at the post mortem or from sweat produced close to the time of the incident. In view of these results we concluded that a single determination should not be used firmly to discriminate long-term exposure to a drug.