Mass spectrometry in the search for new drugs of abuse : method development and clinical application

Abstract

Clinical drug testing using immunochemical screening methodology is limited regarding which analytes are covered. In this thesis, liquid chromatography was investigated as an alternative to immunochemical screening. The developed chromatographic methods were used in authentic urine samples to verify their usefulness and to study the occurrence of novel drugs in various populations.

By using liquid chromatography with UV-detection for screening analysis and liquid chromatography-mass spectrometry for confirmatory analysis of zopiclone and metabolites it was concluded that UV-detection was not selective enough while mass spectrometric detection proved to be more promising. High throughput screening applications were developed, by using direct injection of urine and liquid chromatography-tandem mass spectrometry. The final application included 23 analytes, covering phenylethylamines, nonbenzodiazepine hypnotics and Nbenzylpiperazine and had a capacity of analysing -100 samples per 24 hours.

In a comparison of the mass spectrometry method with an immunochemical assay for the detection of 3,4-methylenedioxy-N-methylamphetamine (MDMA), 1000 samples were analysed. The liquid chromatography-tandem mass spectrometry method was more sensitive and could detect almost four times as many samples as the immunochemical assay. The final multicomponent methodology was applied in studies of 2000 clinical and 1000 forensic urine samples, and samples from heavy drug addicts in a detoxification clinic. Novel findings included zopiclone, zolpidem, zaleplone, N-benzylpiperazine and 1-phenyl-2-butylamine. MDMA was the most common finding followed by zopiclone. In samples from methadone patients only the hypnotics could be detected. Similarly, in the study of 89 heavy drug users, zopiclone were detected in 12% of the samples, but no phenylethylamines and Nbenzylpiperazine. This indicates that heavy drug users are disinclined to use novel drugs.

In conclusion, direct injection liquid chromatography-mass spectrometry proved to be a robust and valuable alternative to immunochemical screening methodology. Many different analytes can be analysed simultaneously, and there is potential of quickly including new analytes. Also, an extensive analytical evaluation generates a more complete picture of the drug abuse in a specific group, and it is important to also analyse less established drugs of abuse if possible. Both positive and negative findings provide valuable information on which substances are abused and which are not.