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1248.0 - Australian Standard Classification of Drugs of Concern, 2011  
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 06/07/2011   
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BUILDING THE CLASSIFICATION

Classification criteria and their application
Main classification structure
Design constraints
Standard code scheme
Reserved codes for residual categories
Supplementary codes

CLASSIFICATION CRITERIA AND THEIR APPLICATION

Classification criteria are the principles by which the classification categories are aggregated to form broader or higher level groupings within the classification structure. In the main classification structure of the ASCDC, these criteria are attributes, characteristics and effects of particular drugs of concern. They are used to establish how the individual drugs are related and how they can most usefully be grouped. The following classification criteria are used to determine the categories of the main classification structure:
  • the similarity of drugs of concern in terms of their chemical structure and the associated mechanisms by which they produce their effects (mechanism of action); and
  • the similarity of drugs of concern in terms of their effect on human physiological activity.

The most detailed level of the classification consists of separately identified drugs, aggregate groups of drugs and residual categories of drugs (see Identifying the Base Level Units of the Classification). These base level units are combined to form the narrow groups of the classification primarily on the basis of their similarity in terms of chemical structure and mechanism of action. For example, Narrow Group 24, Benzodiazepines, contains drugs that all have the same core chemical structure and a similar profile in terms of the broad mechanisms by which they produce their effects. Narrow groups formed in this manner (i.e. comprising drugs of concern that are chemically similar and similar in their mechanism of action), therefore consist of drugs that have similar broad effects on human physiological activity.

In three instances, the similarity of the broad effect of the drugs of concern on physiological activity is used as the primary classification criterion (rather than the similarity in chemical structure and their mechanism of action) when aggregating the base level units to form narrow groups. The Narrow Group 22, Anaesthetics, comprises drugs which are not similar in terms of chemical structure or broad mechanism of action but which form a useful narrow group on the basis of the similarity of their effect on physiological activity. The Narrow Group 56, Atypical Antipsychotics, comprises drugs that have different mechanisms of action but which produce a similar anti-psychotic effect. Similarly, the Narrow Group 91, Diuretics, is formed on the basis of the similarity of the effect of these drugs of concern on physiological activity. The use of the second classification criterion in this way also allows for the formation of meaningful residual categories of drugs of concern at the narrow group level.

At the first and most general level of the main classification structure, broad groups are formed by aggregating narrow groups. This aggregation of narrow groups was undertaken, as far as possible, so that the broad groups consist of narrow groups of drugs of concern which are similar in terms of their effect on physiological activity. For example, Broad Group 1, Analgesics, consists of drugs which have the effect of blocking or relieving pain.

In most cases, the primary physiological system affected by drugs in the ASCDC is the central nervous system (CNS). In instances where drugs of concern are classified on the basis of their similarity of effect on physiological activity, the nature of the effect on the CNS is usually being addressed. The most obvious exception to this principle occurs with Broad Group 4, Anabolic Agents and Selected Hormones, which contains narrow groups of drugs which are similar in terms of their effect on the endocrine system rather than the CNS.

Broad Group 6, Volatile Solvents is formed by the conventional application of the classification criteria as described above. However, the drugs included within this broad group have a similar broad physiological effect to drugs included in Broad Group 2, Sedatives and Hypnotics. Despite this similarity of physiological effect, volatile solvents have been separated from other sedatives and hypnotics.

Broad Group 9, Miscellaneous Drugs of Concern, is a residual category which contains narrow groups of drugs which do not fit into any of the other broad groups on the basis of either of the classification criteria. The two substantive narrow groups contained within this broad group do not exhibit the same broad effect on physiological activity but are considered to be of sufficient importance to warrant separate identification within the main classification structure. This broad group also contains a residual narrow group which will allow for the classification of drugs not currently identified as being of concern and which could not be classified to residual categories in any other part of the classification.

MAIN CLASSIFICATION STRUCTURE

The main classification of the ASCDC has a three level hierarchical structure.

The third and most detailed level of the classification consists of the base units which are separately identified drugs of concern, aggregate groups of drugs of concern and residual categories of drugs of concern (see Identifying the Base Level Units of the Classification). The classification comprises 186 third level units including 17 aggregate groups of drugs and 36 residual 'not elsewhere classified' (nec) categories (see Reserved Codes for Residual Categories below).

The 17 third level aggregate units comprise drugs which do not support individual identification but which are aggregated to form single base level units as they are chemically similar and, when grouped, represent useful categories.

The 36 nec categories contain drugs which are not sufficiently significant, in the current Australian context, to support separate identification or representation as an aggregate base level unit. All drugs which have been identified as drugs of concern, but which are not listed separately or contained within one of the aggregate base level units, are included in the nec category of the narrow group to which they relate.

The second level of the classification consists of 38 narrow groups which contain base level units which are similar in terms of the classification criteria. Included in the 38 narrow groups are six residual 'Other' categories. These residual categories contain base level units which do not belong in any of the alternative narrow groups contained within the broad group on the basis of the classification criteria.

The first and most general level of the classification comprises eight broad groups. The broad groups are formed, in the main, by aggregating narrow groups which are broadly similar in terms of the classification criteria. The classification has one 'Miscellaneous' broad group which comprises narrow groups of drugs which were considered to be of sufficient importance to be included in the classification structure but which do not fit into any of the other seven broad groups on the basis of the classification criteria.


DESIGN CONSTRAINTS

The theoretical and conceptual principles used to develop the main classification structure were applied in conjunction with other considerations such as: the suitability of the ASCDC for the classification of drug-related data from the health, welfare, and crime and justice sectors; the analytical usefulness of data collected within the framework; and the structural and statistical balance of the classification.

An important consideration in developing a classification for statistical purposes is that the structure be statistically balanced. The classification should not have categories at the same level in its hierarchy which are excessively disparate in their population size (the number of classifiable observations or responses each category represents in any application). This allows the classification to be used effectively for the cross-tabulation of aggregate data and for the dissemination of data from sample surveys. Strict application of this principle was not possible in the ASCDC as it was necessary to incorporate the statistical requirements of a diverse range of community activity sectors such as health, welfare, and crime and justice. As a result, not all of the categories of the classification are applicable in all collections and the categories of the classification may not represent a significant number of observations in all applications. For each individual application, the classification, while not necessarily providing an even spread of data across its whole structure, provides a framework that is useful and practical for collecting and presenting data.

One of the more notable constraints in the development of the classification was the practical requirement to represent the diverse range of available drugs of concern within a manageable classification structure. The principle adopted to achieve this end, and to serve the statistical and research purposes of the classification, was to separately identify only those drugs which are of significant concern in the Australian context.

Many of the base level drugs of concern are known by a number of proprietary (brand or trademark) names. Some potential users of the classification indicated they would prefer all these names to be represented in the classification structure for purposes of completeness. While proprietary names are often more readily recognised, it is not practical to have a list of all the known brand names of a drug as the title of each base level unit. As the categories of a classification must be mutually exclusive it is not feasible to identify each brand name as a separate category.

An additional limitation to the use of proprietary names to represent base level units is that many of the more popular or well known brand names are often used, in a generic manner, to refer to all brands of the same product. For example, Panadol to refer to paracetamol, Valium to refer to diazepam, and Prozac to refer to fluoxetine. Therefore, each drug of concern is identified once only in the classification, and where applicable, the base level units reflect the generic name of a drug. Proprietary names are included in the Coding Indexes data cube.

In some instances the generic name of a drug constituting a category of the classification is expressed as an abbreviation of the full chemical name of the psychoactive substance. This is done because of the length of the name or because the abbreviation is more commonly used than the full chemical name. Where abbreviations are used for category names in the main classification structure, the full name is provided in the List of Abbreviations and in the Coding Indexes.

A further factor which influenced the once only representation and titles of the base level units relates to the coverage of the classification. Many drugs can exist in more than one chemical form. Although most are available in their crystalline salt form (hydrochloride, sulphate, citrate, etc.), some are available in their base form. Drugs are also available in different physical forms. As the main classification structure is not intended to classify the form of a drug, substances such as cannabis, hash oil or cannabis resin are all coded to the base level unit, Cannabinoids, which represents the psychoactive compounds common to all the forms of the drug. Similarly, morphine hydrochloride, morphine sulfate and morphine tartrate are all coded to the base level unit Morphine.

Many collectors and users of data relating to drugs of concern require information on the form of a drug as well as the chemical substance. To distinguish between different forms of a particular drug a form of drug classification has been included in the ASCDC Type of Drug Classification and Additional Classifications data cube. The purpose of this classification is to act in conjunction with the main classification structure to further define data relating to drugs of concern without compromising the principles of the main classification structure. The Form of Drug classification allows users to define drugs based on the mode in which the drug exists or is encountered, for example, Powder, Leaf, Granule/rock, or Resin.
STANDARD CODE SCHEME

In the main classification structure, one, two and four-digit codes have been assigned to the first, second and third-level units of the classification respectively. The first digit identifies the broad group in which each narrow group and base level unit is contained. The first and second digits identify the narrow group in which each base level unit is contained. The four-digit codes represent each of the base level units which are separately identified drugs of concern, aggregate groups of drugs of concern and residual (nec) categories of drugs of concern.

For example, the one-digit code 3, denotes the third broad group in the classification structure, Stimulants and Hallucinogens. The two-digit code 31 identifies the first narrow group, Amphetamines, contained within this broad group. The four-digit code 3103 denotes the third base level unit, Methamphetamine, contained within the first narrow group, Amphetamines, of the third broad group, Stimulants and Hallucinogens. This example is presented as follows:
          3 STIMULANTS AND HALLUCINOGENS

          31 Amphetamines
              3101 Amphetamine
              3102 Dexamphetamine
              3103 Methamphetamine
              3104 Amphetamine analogues
              3199 Amphetamines, nec

It should be noted that one, two and four-digit codes ending with 9 are reserved to denote residual categories of the classification at the broad, narrow and base levels respectively (see Reserved Codes for Residual Categories below). A trailing or leading digit 0 is also reserved, for supplementary codes, which are used to process inadequately described responses in statistical collections (see Supplementary Codes below).

As the profile of drug activity in Australia changes it may be necessary to add drugs to, or delete drugs from, the classification structure. If a drug needs to be separately identified in the structure, it will be allocated the next available four-digit code in the narrow group to which it is being added. The available four-digit codes are those ending in the numerals one to eight (four-digit codes ending in zero or nine being reserved for residual categories).

The base level units identified in each narrow group in the original ASCDC were presented in alphabetical order, with the exception of the residual (nec) categories. Where new base level categories have been added to existing narrow groups in the Second Edition, they have been added following the already existing categories, disrupting the alphabetic ordering. If it is necessary to move a base level category from one narrow group to another, it will be allocated the next available code of the narrow group to which it is moved. Its previous code will not be reallocated. See the 'What's changed' section for more information.

The code scheme has been devised so that any future amendments to the structure can easily be accommodated. However, to ensure that the ASCDC remains standard, users of the classification should not make changes to the structure.

RESERVED CODES FOR RESIDUAL CATEGORIES

In most narrow groups of the main classification structure a four-digit code, consisting of the two digits of the narrow group followed by the digits 99, is reserved as a residual 'not elsewhere classified' (nec) base level category. All drugs which have been identified as drugs of concern but which are not separately identified in the classification structure or included in one of the aggregate base level groups, are included in the residual (nec) category of the narrow group to which they relate. Individual drugs of concern are allocated to a narrow group residual category on the following basis:
  • when it is clear that the drug of concern belongs in the particular narrow group on the basis of the classification criteria; and
  • when the drug of concern is a separate entity to the other identified base level units in the narrow group.
In such cases the drug of concern does not warrant separate identification in the narrow group, usually because it was statistically insignificant at the time the classification was developed or last revised.

The main classification structure has 36 residual categories at the base level.

In each broad group, codes are also reserved for residual categories at the narrow group level. These codes consist of the broad group code followed by 9. These categories are termed 'Other' and consist of separately identified drugs of concern which do not fit into any of the narrow groups contained within the broad group, on the basis of the classification criteria. The classification contains six 'Other' narrow groups. No residual narrow group is provided in Broad Group 1, Analgesics, and Broad Group 7, Cannabinoids and Related Drugs, as the narrow groups within these broad groups are logically exhaustive of all drugs within these broad groups.

The main classification structure has one residual broad group which is represented by the initial code 9. It comprises narrow groups of drugs which were considered to be of sufficient importance to be included in the classification structure but which did not fit into any of the other broad groups on the basis of the classification criteria.

It should be noted that residual categories are part of the classification structure and are to be used to classify specific drugs. They are not be be created or used to code responses which contain insufficient information to be accurately assigned to another category of the classification (see Supplementary Codes below and Coding Procedures).

SUPPLEMENTARY CODES

Supplementary codes are used to process inadequately described responses in statistical, administrative and service delivery collections. These codes are of two types:
  • four-digit codes ending with two or three zeros; and
  • four-digit codes commencing with three zeros.

Codes ending in zero are described as 'not further defined' (nfd) codes and are used to code responses to a question about drugs which cannot be accurately coded to one of the base level units but which can be coded to a higher level of the classification structure.

For example, responses which contain insufficient information to be identified as relating directly to a particular drug of concern, but which are known to be within the range of drugs represented by a particular narrow group, are coded to that narrow group. Such responses are allocated an nfd code consisting of the two-digit code of the narrow group followed by 00. For instance, the response Benzodiazepine does not contain sufficient information to be coded directly to any specific drug of concern, but it can be coded to Narrow Group 24 which encompasses all Benzodiazepines. It is thus allocated the nfd code 2400, Benzodiazepines, nfd.

Similarly, responses which do not contain sufficient information to be accurately coded to a specific drug of concern, or to a narrow group, but which are known to be within the range of drugs represented by a particular broad group, are coded to that broad group. Such responses are allocated an nfd code consisting of the single-digit code of the broad group followed by 000. For example, the response Antidepressant, which does not contain sufficient information to be coded directly to any particular narrow group, can be coded to Broad Group 5 which encompasses all Antidepressants and Antipsychotics. It is thus allocated the nfd code 5000, Antidepressants and Antipsychotics, nfd.

Therefore, responses or input data which can only be assigned codes at the broad or narrow group levels of the classification can be processed within a collection at the four-digit or drug of concern level. This allows the coding process to be as precise as the input data quality allows, preserving data that would otherwise be lost and either not coded or coded as inadequately described.

Supplementary codes are listed in Table 2 of the Type of Drug Classification and Additional Classifications data cube.

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