Methadone Detections in Blood Samples from Apprehended Drugged Drivers

Norwegian patients in methadone assisted treatment programs (MATP) are allowed to drive after at least 6 months on an unchanged daily dose. The number of patients in MATP has increased more than ten fold since 1997. By using the nationwide database of the National Institute of Forensic Toxicology on blood concentrations measured in suspected drugged drivers during 1997-2001, all methadone positive cases were identified. These cases had been subject to blood alcohol and drug screening with confirmation and quantification of methadone and other drugs present. These results were used in the present study. The number of suspected drugged driving cases was approximately 3000-4000 per year for the study period, while methadone positive cases increased steadily from 3 in 1997 to 69 in 2001. In most cases from 2000-2002 the blood methadone concentrations measured were compatible with daily dosing up to 150 mg, i.e. within the therapeutic range. In 97% of the cases additional drugs were detected. Flunitrazepam was present in 72% of the samples, often in high concentrations and other benzodiazepines were also abundant, as were tetrahydrocannabinol and amphetamine. Recent heroin use could be stated (6-monoacetylmorphine positive) in 17%, and was suspected in additional 18% of the cases. As a mean between 2 and 3 additional drugs were found in methadone positive samples. Drivers on methadone, suspected of drugged driving, have a more frequently use of additional drugs than has been reported from MATP with urine drug control. This might suggest that those on methadone who also use additional drugs, more likely become impaired and consequently drive in a manner calling attention from the police. Introduction Methadone intake can lead to impaired performance in various psychomotor tests under controlled conditions (1,2). Some dose-effect relation has been demonstrated (1). On the other hand it has been found that these acute effects of methadone will be less pronounced when patients have been using the same daily dose for weeks or months (1,2). As a consequence of these findings, Norwegian patients in methadone assisted treatment programs (MATP) are allowed to drive after approximately 6 months on a stable daily dosage. Until 1997 approximately only 100 patients were enrolled in MATP. This figure has since then increased to 1074 (in 2000) and 1503 in 2001. The sales of methadone in Norway parallels this increase very closely. We wanted to test whether this increasing enrollment into MATP over the later years was reflected in more frequent methadone detections among people suspected of drugged driving by the police, and if that was the case, to find if the suspected subjects represented cases with higher blood methadone concentrations among those given methadone in MATP. This could be done since the Norwegian police for years has demonstrated a rather high detection rate of correctly suspected drugged driving based on close observation of signs and syptoms of impairment followed by forensic toxicological analysis of the suspects blood sample. Most of the cases which have caught the attention of the police have done so because of accidents, reckless and dangerous driving or other deviating driving patterns. Our hypothesis was that increased enrollment of patients into MATP, in spite of careful precautions of permitting driving until stable dosing was achieved, would be reflected in increased numbers of methadone cases among drugged drivers because real traffic could be more demanding than simple laboratory tests, and further that high methadone concentrations would be overrepresented in this material, because of limited tolerance to high doses of methadone. Methods All blood samples from drivers suspected by the Norwegian police for drugged driving are routinely sent to the National Institute of Forensic Toxicology (NIFT) for analysis and interpretation. These samples are subject to alcohol and drug screening with confirmation and quantification of methadone and other drugs by chromatograpic methods, for most drugs with mass spectrometric detection (GC/MS, LC/MS). The samples are accompanied by a drug history of the subject and the results of a 23 item clinical test of drunkenness (CTD), routinely performed by a police physician, at the time of blood sampling. The analytical results are interpreted individually for each suspected driver taking this background information into account. The results are stored in a database at NIFT. By using this nationwide database all methadone positive cases were identified and the results were used for the purpose of the present study. Results The number of blood samples from suspected drugged drivers in which one or more nonalcohol drugs of any type was detected, increased from 2927 in 1997 to 4029 in 2001 (table 1). In the same period samples containing methadone increased from 3 in 1997 to 22 in 2000 and 69 in 2001. Table 1: Blood samples from suspected drugged drivers 1997 1998 1999 200