Dried Blood Spot and mass spectrometry: an analytical tool to certify Cannabis actual state of intoxication

Driving under the influence of Cannabis (DUI) has become a growing concern. Studies investigating the impact of DUI on traffic safety have shown evidence that, during the acute period of Cannabis intoxication, Cannabis diminishes driving faculties greatly increasing the risk of car accidents. However, the actual state of Cannabis intoxication is not easily assessed, particularly in specific contexts such as roadside testing. Until now, the most reliable biological matrix for this purpose in represented by blood but its sampling is invasive and requires a sanitary environment and subsequent treatments or storage precautions, such as centrifugation, refrigeration or freezing. The time lapse between the individuation of a possible intoxication and the blood sampling is very important, since a long delay can mean that, in the meantime, the drug blood levels physiologically decrease under the cut-off value. To overcome this disadvantage, Dried Blood Spots (DBSs) can be a valid alternative to the normal blood sampling by venipuncture. In fact this innovative biological matrix can be obtained after a fast and easy sampling, does not need any particular storage nor transportation precaution and is stable over time. To strictly monitor Cannabis consumption, an original LC-MS/MS method has been developed for the analysis of Cannabinoids in DBSs. Attention has been paid to the determination of Δ9- tetrahydrocannabinol (or THC, Figure 1a), the main psychoactive compound whose presence in blood can be taken as a marker of recent exposure, and its two main metabolites 11-hydroxy-Δ9-tetrahydrocannabinol (THC-OH, Figure 1b) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol. In particular the intermediate hydroxylated metabolite (THC-OH) is pharmacologically active and, at the same time, it is a marker of recent Cannabis intake, since it appears in blood about 13 minutes after consumption and has a relatively short half-life. The carboxylated metabolite (THC-COOH) is not psychoactive and has a very long half-life up to one month for chronic users. For this reason the presence of this latter compound alone in blood cannot be taken as a marker of recent exposure. Is evident, therefore, that the simultaneous monitoring of all the three analytes is necessary to outline pharmacokinetic and toxicokinetic state of abusers and contribute to the assessment of psychophysical state, distinguishing between acute or former consumption. The analytical method developed has been fully validated and applied to real DBS samples from Cannabis abusers with satisfactory results, thus confirming the methodology suitability for roadside testings.