Limitations of the study Conclusions

4.2. Limitations of the study
5. Conclusions
The implications for forensic practitioners who have to interpret THC toxicology from the witness box are challenging. THC kinetics in heavy users appears to be highly variable and there is no easy interpretation which will allow a useful estimation of time of use from a single measurement. The daily THC blood concentrations and urinary THC-COOH concentrations both showed expected patterns of monotonic decline over the whole seven days of the study. However the high daily variation in each makes it challenging to interpret these levels in the usual forensic situation where there is usually only one measurement of these analytes available from a single set of specimens taken at a variable PHA-680632 after an incident under forensic investigation.
α-PBP; Cathinone; Human phase I metabolism; Urine; LC–MS/MS; GC–MS
1. Introduction
Information about the metabolic pathways of α-pyrrolidinophenones is indispensable for regulating recreational use and determining the cause of death and poisoning in forensic or toxicological studies. Shima et al. [7] analyzed 19 urine samples obtained from α-PVP abusers and reported that the main metabolic pathways in humans included reduction of the ketone group and oxidation of the pyrrolidine ring. Springer et al. [4] and [5] and Peters et al. [6] reported the rat metabolism of α-PPP, MPPP and MPBP. α-PPP was metabolized extensively via reduction of the ketone group, oxidation of the pyrrolidine ring, 4′-hydroxylation of the phenyl ring, and degradation of the pyrrolidine ring to the primary amine [4]. The common metabolic pathways of MPPP and MPBP are hydroxylation of the tolyl group followed by oxidation to the corresponding carboxylic acid, oxidation of the pyrrolidine ring, and oxidative deamination [5] and [6].