The misuse of mephedrone (4-methylmethcathinone) has been increasing greatly in Western countries over the last two years or so, especially in the club and dance scenes. This period has also been marked by claims that the substance has been implicated in a rising number of deaths in the USA and Western Europe, especially the United Kingdom (UK).

This chapter explores the context(s) and evolution of mephedrone use in the UK, and the circumstances in which these fatalities occurred. Particular attention is paid to the settings in which these incidents took place, their symptomatology and physical characteristics; intervention/treatment opportunities; and toxicological and pathological findings. These results are related to the known pharmacological facts regarding mephedrone, its possible interactions with alcohol and other psychoactive drugs, and suggested clinical interventions and treatment(s).

The relationship between mephedrone, other methcathinones, and other emerging novel psychoactive substances, as well as established stimulants is also examined. These developments are important as novel substances used for recreational use become more globally accessible through the use of the Internet.