When I use a word . . . The languages of medicines—defining a street drug operationally

Defining street drugs

I have previously discussed the difficulties in coining a dictionary-type definition of the term “street drug,”1 largely because there are two problems with the term: one is the word “street” and the other is the word “drug.”

On the street

Street names are colloquial names that some drugs are given. The definition that the Oxford English Dictionary (OED) gives for the street name of a street drug is “the (slang or colloquial) name under which a drug is known or sold on the street.” This implies that if a drug has a colloquial name it must be a street drug. But street drugs need not be sold at all, and even if sold the sale need not occur on or in the street. You might, for example, obtain a street drug in a park, or in a room in an apartment block, or in some other comparable place, or via the internet, or conceivably even in a pharmacy. Nor does a drug have to have a colloquial name for it to be regarded as a street drug. It could equally well be referred to by its International Nonproprietary Name; ketamine is a good example, although it has colloquial names as well. And some drugs that are not street drugs have colloquial names too, e.g. statins.

Which drugs?

It is equally difficult to define the specific drugs that qualify under the heading of “street drugs.” Others have identified a range of categories from a systematic review,2 each of which might individually define a street drug: recreational, illicit, or dangerous drugs, those with alternative names derived from “street slang,” those unprofessionally manufactured, and those that contain impurities or adulterants. However, no one category provides a unique definition.

In addition, several types of descriptions of drugs have been proposed in seeking an alternative name for street drugs.2 One can for example, distinguish “hard” drugs (e.g. heroin and cocaine) from “soft” drugs (e.g. cannabis, amfetamines), or categorise certain drugs as “illicit drugs,” or “designer drugs,” or “party drugs.” None of these, however, solves the problems of defining a street drug, or even offers a suitable alternative term to define.

A much better way of distinguishing different types of drugs is by indicating their main mechanisms of action. Indeed, that is the chief method whereby International Nonproprietary Names are coined nowadays, whenever possible.3 Only if that is not possible is the chemical nature of the compound used as an indicator. However, similar problems arise in trying to use this as a method of defining a street drug. The technical details are hard to understand and in any case some drugs in a mechanistic class may be used as street drugs and others not.

A first attempt

Having discussed the various problems with all the definitions hitherto proposed, I finally suggested the following definition: “a medicinal product supplied or sold by one who is not legally permitted to do so.” 1

However, I also recognised the problems inherent in this definition. For instance, it would not cover all cases—supply and possession of cannabis, for example, is legal in some places and not others; cannabis would be a street drug here but not there; alcohol and nicotine products illegally sold on the street would be regarded as street drugs, although they are generally legally available. It is also possible for other drugs, legally available from a pharmacy, with a prescription, to be illegally supplied in other ways, without making them susceptible of description as street drugs.

Other ways of dealing with the problem are needed.

Types of definitions

It appears from this that there is no good definition of a street drug. However, before we reach that conclusion, we must exhaust the definitional possibilities.

I have previously described seven different types of definitions4: nominal definitions (two types), descriptive definitions, stipulative definitions (which can be either intensional or extensional), operational definitions, and ostensive definitions. Three of these are potentially relevant to the definition of a street drug: intensional, extensional, and operational definitions. Hitherto we have considered only the type of definition known as an intensional definition (intentionally spelt with an ess).

Intension and extension in logic were first defined by Sir William Hamilton, professor of logic and metaphysics in the University of Edinburgh, in lectures that he gave there, starting in 1836: “The Internal Quantity of a notion, its Intension or Comprehension, is made up of those different attributes of which the concept is the conceived sum; that is the various characters connected by the concept itself into a single whole in thought. The External Quantity of a notion or its extension is, on the other hand, made up of the number of objects which are thought mediately through a concept.”

From this came intensional and extensional definitions. An intensional definition is one that embodies all the attributes contained in the concept being defined in a single short statement. In contrast, an extensional definition enumerates all the individual components of which the thing being defined consists. Most bioscientific definitions are intensional.

Take the example of a diary. It can be intensionally defined as “A book prepared for keeping a daily record, or having spaces with printed dates for daily memoranda and jottings; also, applied to calendars containing daily memoranda on matters of importance to people generally, or to members of a particular profession, occupation, or pursuit.”5 However, I might define a specific type of diary extensionally by describing all the features that it contains. My Oxford University diary, for example, includes the dates of the full university terms, calendars, spaces for recording the titles of lectures, the dates of various holidays and religious feasts, spaces for diary entries, the names of university officers, addresses of university departments, libraries, colleges, and other institutions, and details of local bus services. That’s an extensional definition.

An operational definition is different. It describes how things happen, first one thing, then the next, and then the next; it is created by describing all the processes involved in the order in which they occur, and it can be afforced by the addition of other relevant information, such as causes and contributory factors. When Manfred Hauben and I essayed a definition of a signal in pharmacovigilance, we surveyed previous intensional definitions, to identify a signal’s essential features, and constructed an operational definition, from all of which a final intensional definition emerged.6

In contrast, when Carl Heneghan, Robin Ferner, and I tackled the problem of defining a drug shortage, we found that the problems are too complicated to be encompassed in a brief intensional dictionary-style definition; we therefore proposed an extensional operational definition that incorporates the processes by which medicinal products are manufactured and distributed, the causes of shortages, and their many contributory factors. The diagrammatic definition that resulted shows operationally how shortages come about and extensionally what the causes and contributory factors are.7

Defining street drugs extensionally

If an intensional definition of a street drug is inadequate, would an extensional definition work?

It is certainly possible to list all the compounds that might qualify, and such a list already exists, in the UK Home Office’s incomplete list of 500 compounds that are encompassed by the different classes of drugs defined in the Misuse of Drugs Act 1971 and the Misuse of Drugs Regulations 2001, from acetorphine to zopiclone, 220 in class A, 104 in class B, and 176 in class C.8 A more complete list can be found in Parts I, II, III, and IV of Schedule 2 to the 1971 act and in Schedules 1 to 5 to the 2001 regulations. One problem with such a list in relation to the definition of a street drug is that many of the listed compounds are prescribable drugs, sale or supply of which without a prescription would be illegal, but which are not themselves used in the ways that street drugs are used. Furthermore, the list of itself can hardly be said to constitute a definition of a street drug or even the whole world of street drugs, in the way, for example, that my diary is defined by its list of contents.

A list of the features that might collectively define a street drug could be compiled from the kinds of terms discussed above (recreational, illicit, etc), and such a list would in theory constitute an extensional definition of a street drug. However, different street drugs have widely different characteristics—neither would the complete list be relevant to every drug, nor would it be possible to say for any individual drug which subgroup of characteristics from the complete list defined that drug. A table could be compiled showing for any drug the factors that conferred on it the distinction of being a street drug. However, such a table would be relevant only to a given legal jurisdiction.

Defining street drugs operationally

For a more generally applicable definition, we need something different, and what we need, I think, is in fact an operational definition. Such a definition would start by describing the sources of the materials from which the products are manufactured, continue with an account of the manufacturing processes, and detail the methods of wholesale distribution and of end-user sale and supply. It might also include the methods of use, listed extensionally, with examples.

Then we would have a definition of a street drug, which could be illustrated by specific drugs that come under the heading in specific circumstances, giving a composite definition of any particular drug in its role as a street drug.

To put it briefly, a street drug would be best defined not by what it is but by how it becomes what it is.