Chemical and Pharmacological Classification

As will be seen from the above discussion, novel substances are mostly synthetic compounds. This was clearly the focus of the 1997 EU Joint Action, and is reflected in what has been seen world-wide over the past few decades. However, the 2005 EU Council Decision broadened the scope to include, for example, herbal products (see Chapter 14, ‘Natural product (fungal and herbal) novel psychoactive substances’) and even medicines. Only a few plants/fungi or their extracted products have been reported since 2005; they include Salvia divinorum, which contains the hallucinogen salvinorin-A, Piper methysticum (kava kava; active principals kawain and related substances), Tabernanthe iboga (ibogaine), Areca catechu (betel nut; active principal arecoline) and Mitragyna speciosa (kratom; active principles mitragynine and 7-hydroxymitragynine). There are many other plant extracts that might be added to this list, some of which contain established scheduled drugs, for example, Diplopterys cabrerana, Psychotria viridis and Mimosa hostilis (N,N-dimethyltryptamine), Catha edulis (khat; cathinone), and Psilocybe semilanceata and other ‘magic’ mushrooms (psilocin and psilocybin). However, most of these ‘non-synthetics’ pose particular legal problems and are rarely amenable to an all-encompassing control regime. Many legislatures are reluctant to specify herbal materials beyond the traditional products (e.g. cannabis, coca leaf and opium), because of the botanical, taxonomic and physical difficulties that can arise in their identification.

It is sometimes useful to consider solvents and gases, such as nitrous oxide (laughing gas), alkyl (now mostly isopropyl) nitrite (poppers), aliphatic hydrocarbons (e.g. cigarette lighter fuel) and aromatic hydrocarbons (e.g. adhesive solvents) within the group of novel psychoactive substances. But solvents and gases, particularly when used by inhalation (contrast ingestion of the solvent GBL, gamma-butyrolactone) pose problems with analysis and proof of possession by virtue of their high vapour pressures. That said, some volatile substances are amenable to restrictions on supply. In the UK, the Intoxicating Substances (Supply) Act 1985 [22] makes it an offence for a retailer to sell solvents to anyone under the age of 18, knowing that they are being purchased to be abused. It does not make it illegal to buy or own solvents. The Cigarette Lighter Refill (Safety) Regulations 1999 [23] – an amendment to the Consumer Protection Act 1987 – makes it illegal to supply gas cigarette lighter refills to anyone under the age of 18. Furthermore, European Directive 2005/59/EC of 26th October 2005 prohibits the placing on the market, for sale to the general public, the substance toluene and adhesives and spray paints containing in excess of 0.1% toluene [24]. Nitrous oxide has clinical use as an anaesthetic, but is also a commercially-available foaming agent for dairy cream, where restrictions on the small pressurised containers would be difficult to enforce. Attempts in the UK to classify alkyl nitrites (other than the once clinically-useful amyl nitrite) as medicinal products have so far been unsuccessful.

Active pharmaceutical ingredients and medicinal products in general represent a further group that can fall under the heading of ‘novel psychoactive substances’. It is not usually the established use of such products that is the cause for concern, but rather their unlicensed consumption, often in pharmaceutical forms or routes of administration that differ from those authorised. Examples here include dextromethorphan (DXM), a common antitussive when used in small quantities (e.g. 10 mg), which is alleged to produce psychoactive effects when 100–200 mg are ingested. Illicit tablets containing large amounts of DXM are now rarely seen. Ketamine (Chapter 12), when in the form of injection ampoules, is an established licensed medicinal product for use as an analgesic and anaesthetic, but tablets and white powders are unlicensed products that may be ingested or snorted. Other pharmaceutical ingredients that have been notified to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) under the terms of the Early Warning System include phenazepam, pyrazolam and etizolam (none of which is included with other benzodiazepines in the UN 1971 Convention), pregabalin, benzydamine, glaucine and GHB (gamma-hydroxybutyrate). It is appropriate in this context to mention misuse of licensed cognitive enhancers, the most common example of which is modafinil. Apart from the US, this licensed medicine is not commonly subject to drug legislation, but is widely misused, and is available through similar Internet channels as other novel substances. The European Medicines Agency announced in November 2011 that the use of modafinil should be restricted to the treatment of narcolepsy. The review by the Agency’s Committee for Medicinal Products for Human Use (CHMP) was initiated because of a number of safety concerns, relating to psychiatric disorders, skin and subcutaneous tissue reactions as well as significant off-label use and potential for abuse [25].

As noted earlier, the detailed pharmacological properties of many novel substances are unknown, but in terms of general effects it is clear that users seek out substances which are primarily central nervous system (CNS) stimulants like amphetamine or behave as entactogens and empathogens like 3,4-methylenedioxymethamphetamine (MDMA). The synthetic cannabinoid receptor agonists are often smoked as substitutes for cannabis, but hallucinogens are less common, while novel narcotic analgesics are now rare.