Over the last two decades, the drug market has dramatically changed, posing unpredictable public health risks and a significant burden on national health and social care services. In England and Wales, the number of deaths related to substance misuse has increased by 3.5-fold from 831 in 1993 to 2917 deaths in 2018, a 16% increase from the previous year [1]. The illicit market has become increasingly complex, particularly with the global emergence of New/Novel Psychoactive Substances (NPS), drug use trends, easy online access to illicit substances, peer reviews and limited technologies for the identification and monitoring of novel substances. In response to these challenges, harm reduction interventions are essential to promote public health and prevent avoidable premature deaths from substances [2,3]. The International Harm Reduction Association defined “harm reduction” as “policies, programmes and practices that aim primarily to reduce the adverse health, social and economic consequences of the use of legal and illegal psychoactive drugs without necessarily reducing drug consumption” [2].

Lefkovits (2016) proposed various harm reduction interventions. These include on-site drug checking, monitoring through establishing an early warning system and publishing police seizure data. The latter is not widely implemented as it may be viewed as promoting drug use [4]. In contrast, the former “drug checking”, also known as “pill testing”, “street drug analysis”, “adulterant screening”, “multi-agency safety testing” and “drug safety testing” [5,6,7], is a model of harm reduction that can be provided at the point of care. Drug checking involves drug analysis to identify the content and/or purity of the drug sample, then the provision of analysis results are directly communicated to individuals through a harm reduction consultation, an online report and/or official channels to cascade alerts from a potentially lethal substance [7,8]. A global review was undertaken in 2017 and identified 31 drug checking services in 20 different countries [6,9]. In 2018, Oute et al. also carried out a comprehensive review of drug checking services based within the nighttime economy [8]. An updated review of drug checking services was carried out by Guirguis et al. (2020) [10]. In these reviews, established drug checking services were compared with respect to their impact and limitations. In addition, the latter review captured the general public’s perceptions on drug checking via Twitter [10].

Although there are claims that drug checking lacks a robust evidence base regarding its effectiveness [3,8,11], based on Public Health England’s “drug alerts—evidence for effectiveness”, drug checking has been proven to be effective in reducing use [12], including “harmful use and limiting specific substance use amongst certain user groups”. Streetwork, the youth advisory service in the city of Zurich, evaluated their on-site and stationary drug checking facilities, demonstrating that drug checking coupled with a consultation contributes to harm reduction and prevention, particularly for those individuals with frequent re-dosing patterns and polysubstance use [13]. Although not all drug checking techniques are conducted to a “forensic standard”, they have been shown to reduce risky consumption behaviours [11,14]. Drug checking has also been shown to enable engagement of individuals who are not in treatment [15] and has provided drug education focusing on “safer drug use” [16]. It is also claimed that drug checking services can “shift and stabilise” the drug market since individuals can consequently make more informed decisions related to the drugs they are buying and/or intend to consume [11]. Drug checking services have obvious positive effects. These positive effects include: (1) reducing harms from drugs by enabling a dialogue through consultation and counselling about their consumptions patterns and drug-taking behaviours; (2) enhancing the monitoring of drug trends through drug analysis; (3) monitoring of the emergence of novel substances; (4) improving access to healthcare and substance use treatment services; and (5) improving sharing of information with relevant stakeholders [5,8,13,17]. However, drug checking has been a “controversial” harm reduction activity and may have negative effects by implying the normalisation and safety of drug use and limited accuracy of findings, for example by overestimating drug concentrations [3,8,18].

The first drug checking service was established in the early 1990s in Europe to reduce harms from NPS, and the first drug checking service that combined drug testing with harm reduction interventions was Drug Information and Monitoring System (DIMS) established in the Netherlands in 1992 [19]. Typically, “drug checking services” invite recreational users to anonymously submit a sample of an illicit substance for analysis and aim to deliver harm reduction advice to the person who provided the sample, based on the sample’s identified content (type of drug(s) and/or purity) [6,8]. Drug checking can be “front-of-house” or “back-of-house” testing [7]. The former refers to a service where individuals attend the on-site drug checking service, at festivals for example, and personally engage with the team conducting the service. It usually targets people who use substances and aims at reducing harms in the nighttime economy [7,8]. In contrast, the latter refers to a service, where individuals may anonymously send drug samples for analysis and the results may be published on the service’s website to raise awareness about a drug type [7]. Back-of-house does not usually involve a direct interaction between the team conducting the service and the individual bringing a drug sample for analysis. It may also involve drug samples from police seizures. Back-of-house predominantly aims at monitoring trends in the drug market and providing wider non-targeted harm reduction messages [7,8]. Drug checking may be on-site providing a “screening” grade analysis or laboratory-based providing “confirmatory” analysis. This primarily depends on the technologies employed and available resources, which in turn can significantly impact associated costs, the analysis time and the quality of the results [4,11,20].

Drug checking services have taken place at a variety of settings including within the nighttime economy, music festivals, shopping centres and in laboratories. In the UK, in 2009, WEDINOS (Welsh Emerging Drugs & Novel Substances Project) was the first service to collect unknown substances from substance misuse services (SMS), housing and hostels, youth clubs and young people’s services, night clubs and bars, mental health services, Local Authorities, Ambulance Service and the Police. WEDINOS tests the substances in laboratories using confirmatory analysis techniques, produce and disseminate pragmatic harm reduction advice, based on the content and legal context, via their website, health alerts via press releases and their quarterly bulletin. Recently, The Loop has been testing drugs predominantly at UK music festivals using on-site screening techniques and has demonstrated the need for such services to be providing harm reduction advice in such settings [21]. WEDINOS operates under a Home Office licence and provides a free service, which is funded by the Welsh Government, whereas the latter is a volunteer-led service, which operates without a Home Office licence and, instead, in collaboration with relevant local police forces under “an exception to legal restrictions”.

The technological and analytical capacity of the testing along with tailored counselling plays a key role in the success of a drug checking service. Numerous reports have compared and evaluated various screening and confirmatory technologies that are employed in drug checking services [4,6,8,11,20]. These techniques include colorimetric reagent testing, Fourier-Transform Infrared Spectroscopy (FTIR), Capillary Electrophoresis (CE) with Ultraviolet Spectroscopy (UV), High-performance Liquid Chromatography (HPLC) with UV or Mass Spectrometry (MS) detection, Gas Chromatography with MS detection (GCMS), Ion Mobility Spectrometry (IMS) with MS detection and Matrix-assisted laser desorption ionisation (MALDI) Orbitrap MS [8,22]. These techniques vary in their ability to detect different substances, multiple compounds at once, low drug content in complex mixtures such as designer fentanyls, quantitative analysis, previously unknown substances, analysis time, portability, reliability, ease of operability, cost and suitability for a particular setting [4,6,8,11,20]. Despite that laboratory-based MS methods are the gold standard, presumptive techniques such as colour tests may enable initial harm reduction conversations. Given the limitations of in-field screening techniques with respect to false positive and false negative results, they can still help to engage people who use drugs in a dialogue about their consumption patterns, which can then lead to positive behaviour change. It is important to note that the cost of operation is very high, and that gold standard methods may not be viable for these services.

In addition, the choice of the technology depends on the purpose of the analysis, for example, whether the analysis aims at identifying the psychoactive substance only or whether the analysis aims at identifying all the constituents in a drug sample or providing quantitative analysis. The quality of the outcomes not only depends on the suitability of the technology but also on the personnel undertaking the analysis and their level of expertise. The quality of the drug checking is enhanced not only by the drug checking activity itself but also by the use of the results, i.e., whether the results will be used to provide individual harm reduction intervention(s), issuing public health alerts, disseminating harm reduction information and/or surveillance of the drug market [11]. Harper et al. (2017) recommended Infrared and Raman as the best technology for on-site drug checking. In this paper, evaluation of the technology employed for the analysis of drug samples is not discussed and will be thoroughly covered in a subsequent analytical paper.

Drug checking services are deemed important as drug-related deaths are at concerning levels [1]. In addition, the emergence of batches laced with potent and potentially harmful substances such as Spice and fentanyl derivatives continue to affect marginalised and vulnerable groups, with no sign of abating [23,24]. The frequency, variety and chemical diversity of newly available substances as well as their unpredictable adverse effects are posing acute public health risks [25]. These risks are particularly evident for NPS, as over 900 new substances have emerged in the last decade, thus making drug use more dangerous and communicating accurate harm reduction advice even more challenging [25].

This paper presents learnings from a pilot service that follows the UK Government’s agenda to prepare and respond to future threats caused by NPS [26]. It is also in line with the Royal Pharmaceutical Society’s guidance documents developed by the authors of this manuscript [27]. We believe drug checking services are important harm reduction strategies. In the UK, drug checking services have never been undertaken in a clinical setting or coupled with clinical interventions or under a Home Office licence for field drug detection. Therefore, the aim of this work was to scope the feasibility of setting up and providing a pharmacist-led Home Office-licensed drug checking service in a community SMS environment using a portable screening laboratory. The project’s objectives were to engage individuals in treatment and provide tailored harm reduction interventions including provision of take home naloxone, injecting paraphernalia, psychosocial and prescribed treatment interventions, signposting individuals to appropriate sources of help and support and avoiding drug related harms by enabling more prompt responses to potential “bad batches” using existing alert cascade processes (including interface with Public Health England and NHS England Controlled Drug Local Intelligence Network protocols).