Clinical toxicology of newer recreational drugs

Introduction. Novel synthetic 'designer' drugs with stimulant, ecstasy-like (entactogenic) and/or hallucinogenic properties have become increasingly popular among recreational drug users in recent years. The substances used change frequently in response to market trends and legislative controls and it is an important challenge for poisons centres and clinical toxicologists to remain updated on the pharmacological and toxicological effects of these emerging agents. Aims. To review the available information on newer synthetic stimulant, entactogenic and hallucinogenic drugs, provide a framework for classification of these drugs based on chemical structure and describe their pharmacology and clinical toxicology. Methods. A comprehensive review of the published literature was performed using PUBMED and Medline databases, together with additional non-peer reviewed information sources, including books, media reports, government publications and internet resources, including drug user web forums. Epidemiology. Novel synthetic stimulant, entactogenic or hallucinogenic designer drugs are increasingly available to users as demonstrated by user surveys, poisons centre calls, activity on internet drug forums, hospital attendance data and mortality data. Some population sub groups such as younger adults who attend dance music clubs are more likely to use these substances. The internet plays an important role in determining the awareness of and availability of these newer drugs of abuse. Classification. Most novel synthetic stimulant, entactogenic or hallucinogenic drugs of abuse can be classified according to chemical structure as piperazines (e.g. benzylpiperazine (BZP), trifluoromethylphenylpiperazine), phenethylamines (e.g. 2C or D-series of ring-substituted amfetamines, benzodifurans, cathinones, aminoindans), tryptamines (e.g. dimethyltryptamine, alpha-methyltryptamine, ethyltryptamine, 5-methoxy-alphamethyltryptamine) or piperidines and related substances (e.g. desoxypipradrol, diphenylprolinol). Alternatively classification may be based on clinical effects as either primarily stimulant, entactogenic or hallucinogenic, although most drugs have a combination of such effects. Clinical toxicology. Piperazines, phenethylamines, tryptamines and piperidines have actions at multiple central nervous system (CNS) receptor sites, with patterns of effects varying between agents. Predominantly stimulant drugs (e.g. benzylpiperazine, mephedrone, naphyrone, diphenylprolinol) inhibit monoamine (especially dopamine) reuptake and are characteristically associated with a sympathomimetic toxidrome. Entactogenic drugs (e.g. phenylpiperazines, methylone) provoke central serotonin release, while newer hallucinogens (e.g. 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DiPT), 2,5-dimethoxy-4-bromoamfetamine (DOB)) are serotonin receptor agonists. As a result, serotoninergic effects predominate in toxicity. Conclusions. There are limited reliable data to guide clinicians managing patients with toxicity due to these substances. The harms associated with emerging recreational drugs are not fully documented, although it is clear that they are not without risk. Management of users with acute toxic effects is pragmatic and primarily extrapolated from experience with longer established stimulant or hallucinogenic drugs such as amfetamines, 3,4-methylenedioxymethamfetamine (MDMA) and lysergic acid diethylamide (LSD).