1 INTRODUCTION

Since the discovery of LSD's (lysergic acid diethylamide) psychoactive effects by Albert Hofmann in 1943, this substance has been widely available as a tool for exploration of the mind, as a potential medicine and as a recreational drug (Hofmann, 1980; Smith, Raswyck, & Davidson, 2014). Despite public perception of LSD as a dangerous psychedelic, from a physiological standpoint it has one of the safest profiles of this drug class (Nichols, 2016). In a recent review, Nichols (2016) stated that there are no known deaths arising from LSD toxicity even in severe intoxications. Indeed, safety protocols have been developed to guide the use of LSD in human trials (Johnson, Richards, & Griffiths, 2008), including for LSD‐assisted psychotherapy for patients with life‐threatening diseases (Gasser et al., 2014).

Currently, LSD is a prohibited drug according to the United Nations Conventions (United Nations Office on Drugs and Crime, 2013). As a consequence, the supply of LSD for use as a recreational drug is not subject to manufacturing regulations. In such unregulated markets, the risks of prohibited drugs to human health are amplified: in addition to the risks of consuming a “standard” dose, additional risks arise from consuming an unexpected hazardous substance or substance combination. The use of blotter paper to distribute LSD limits the possible active substances that can feasibly be used as a substitute to compounds with low threshold dosages. In the 1960s when LSD first appeared in street markets, it remained unique regarding its potency and psychedelic effects. After the discovery of DOM's (2,5‐dimethoxy‐4‐methylamphetamine) effects, and from its homologue halogenated series, with bromine (DOB), chlorine (DOC) and iodine (DOI) in fourth ring position, these highly potent and long‐lasting psychedelic amphetamines have been intermittently detected in blotter samples sold as LSD (Brown & Malone, 1976; Brunt & Niesink, 2011; Grifell et al., 2015; Renfroe & Messinger, 1985; Snyder, Faillace, & Hollister, 1967).

The level of misrepresentation among alleged LSD samples has been measured over time through community‐based drug analysis, testing or checking programmes. In the 1970s and 1980s, U.S.‐based testing programmes detected that most alleged LSD did contain only the expected substance: 92% of 746 samples (Brown & Malone, 1976) and 88% of 1,845 samples (Renfroe & Messinger, 1985). Where unexpected substances were detected, they included phencyclidine, DOB, DOM, amphetamine and caffeine (Brown & Malone, 1976; Renfroe & Messinger, 1985). In the first decade of the 2000s, the trends were similar. The Dutch Drug Information and Monitoring Service, which includes a drug‐checking programme, reported that 85% of the 638 alleged LSD samples from 1999 to 2010 contained only the expected substance. The year 2002 was an exception, where among 40 alleged LSD samples, only 10 contained LSD, with many of the remainder containing DOB (Brunt, 2016; Brunt & Niesink, 2011). Between 2009 and 2013 in Portugal, drug‐checking services tested 105 alleged LSD samples, finding 91% contained only LSD, and the remainder containing psychedelic amphetamines such as DOI and DOB (Martins, Valente, & Pires, 2015). Since 2012, a newer phenethylamine series (N‐benzylphenethylamine—25x‐NBOMe) has been repeatedly detected in expected LSD samples (Caldicott, Bright, & Barratt, 2013; Vidal‐Giné, Fornís‐Espinosa, & Ventura‐Vilamala, 2014). While the overall proportion of alleged LSD samples that contain these unexpected substances remains low, drug‐checking service data where DOx and 25x‐NBOMe are detected show that these drugs are sold as LSD. For example, in Spain from 2012 to 2015, 25I‐NBOMe was detected in 56 samples, 43% of which were alleged to be LSD (Ezquiaga et al., 2016). In the same Spanish service from 2009 to 2014, DOC was detected in 41 samples, 42% of which were alleged to be LSD (Grifell et al., 2015).

Unintentional consumption of DOx and 25x‐NBOMe may pose a high risk of acute toxicity or even death (Nichols, 2016). There are several reports of both acute and fatal intoxication after consumption of some of these compounds (Balikova, 2005; Barnett et al., 2014; Burish, Thoren, Madou, Toossi, & Shah, 2015; Hill et al., 2013; Nikolaou, Papoutsis, Stefanidou, Spiliopoulou, & Athanaselis, 2015). Recently, a review of intoxication cases associated with N‐benzylphenethylamine derivatives was published (Suzuki et al., 2015). From the 20 cases studied, seizures were reported in eight cases and three cases resulted in death. At this moment, there is not robust data to conclude if reported deaths related to consumption of DOx and 25x‐NBOMe resulted from lethal amounts of the pure substance or an inherent toxicity, regardless of dose (Nichols, 2016). However, compared with LSD toxicological data of almost 70 years of medical and recreational use, at least it can be reasonably argued that their consumption is associated with greater risk.

As shown in the above review of LSD misrepresentation, drug‐checking services provide information useful for drug market monitoring. This information is unique because such services can access a different and arguable wider range of drug samples to those accessed through police seizures (Camilleri & Caldicott, 2005), and they provide information about the nature and size of the discrepancy between alleged and actual chemical content of drugs (Barratt & Ezard, 2016). In the last decade, with the increased availability of new psychoactive substances (European Monitoring Centre for Drugs and Drug Addiction, 2016), the provision of mechanisms to screen and identify these substances is of utmost importance. In addition to their use in monitoring drug trends, drug‐checking services can also change consumer behaviour at point of consumption (i.e., when the consumer is confronted with an unexpected test result, see Benschop, Rabes, & Korf, 2002; Sage, 2015), inform clinical management at the point of intervention (Butterfield, Barratt, Ezard, & Day, 2016), and facilitate brief intervention and referral to services (Hungerbuehler, Buecheli, & Schaub, 2011).