Synthetic Cannabinoids and Cathinones: Prevalence and Markets. 
Over the past few years, the phenomenon of new designer drugs has attracted much attention.  Synthetic cannabinoids and cathinones are the two main classes of these drugs.  Both are potent drugs of abuse, and several cases of severe toxicity and deaths are reported.  The present work is based on a systematic review of studies that have assessed the market and prevalence of synthetic cannabinoids and cathinones, and integrates pharmacological, sociological, and epidemiological aspects of these two groups of emerging synthetic drugs.  The review reflects that the Internet has made synthetic cannabinoids and cathinones widely available.  Furthermore, aggressive and widespread marketing, as well as the low price level of these drugs, their juridical status and their lack of detection on standard drug tests may serve as major motivations for drug use.  The number of prevalence studies is small and derived from a limited number of countries.  In spite of the many methodological shortcomings, some conclusions may be cautiously drawn.  Taken together, the results point toward higher prevalence of use for synthetic cathinones than for synthetic cannabinoids.  In the general population, the prevalence of use of synthetic cathinones is reported to be around 4% compared to figures lower than 1% for synthetic cannabinoids.  Among students, the prevalence varies from 1-20% for synthetic cathinones and 2-10% for synthetic cannabinoids.  Among groups with high rates of drug use, the prevalence varies between 4% to more than 60% for synthetic cathinones and around 10% for synthetic cannabinoids.