The role of syringe residue analysis in identifying substances consumed in sexualized drug use practices.

Chemsex is a practice mostly extended between men who have sex with men under drugs effects to enhance and/or prolong sexual activities. Within chemsex, slamming consists of intravenous consumption of substances such as cathinones and amphetamines. Syringe residue analysis is a relatively new alternative for knowing with accuracy the substances consumed by the users. Although several studies have been carried out applying the technique, none of them was focused on this population group. In this work, syringes were obtained from a drug addiction assistance centre from Madrid (Spain). Samples were processed by rinsing with methanol and injected in a liquid chromatography coupled to high resolution mass spectrometry system. Data (acquired in data dependent mode) were processed using a suspect screening approach. In total, 122 syringes from three sampling campaigns were analyzed. The compounds belonging to the cathinones' group were the most frequently detected (99 %), followed by amphetamines and cocaine. The most consumed cathinone was chloromethcathinone, but also others as methylmethcathinone, pentedrone or N,N-dimethylpentylone were identified. Furthermore, temporal trends were detected during the different sampling campaigns. Thus, this technique allowed us to determine in an accurate way the substances consumed during slamming sessions, which may differ from the self-declared ones in surveys. Moreover, temporal trends were observed, that align with the market changes and regulation of cathinones.