Report of the Independent Inquiry into the Misuse of Drugs Act 1971

Drug Classification - pages 55 - 60

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Our recommended approach

  1. We believe that the present classification of drugs in the MDA should be reviewed to take account of modern developments in medical, scientific and sociological knowledge. The main criterion should continue to be that of dangerousness but the criteria should be made clear. The relative dangerousness of drugs is determined by a number of factors, some applying to the individual, others to society. The main justification for controlling drugs lies in the harm that their use causes to society. However, we should make it clear that, as a matter of principle, it is right for the law to take into account harm that drugs cause to users themselves, as well as to other people affected by users or to the community at large. It is widely agreed that there are cases in which the law may properly try to protect people from harming themselves. These are cases – seatbelts and motorcyclists’ helmets are examples – in which the damage is serious, almost always comes about unintentionally, and is hard to reverse. This is the kind of risk that is associated in varying degrees with dangerous drugs, and the case is even stronger to the extent that they take away the power of choice. For these reasons, we think, as most people do, that the law should take into account the harms that drugs do to the people who use them. In any case, it is impossible in fact to separate harms to users from harms to others; self-inflicted damage usually results in costs to others. The harm to the individual as a consequence of the pharmacological effects of a drug lends itself best to objective evaluation. Initially at least, this harm is likely to be the best indicator of how strictly a drug needs to be controlled.
  2. Personal harm may be assessed on the basis of four factors:
  1. risks of the drug itself: acute (short-term) and chronic (long-term) toxicity;
  2. risks due to the route of use;
  3. extent to which the drug controls behaviour (addictiveness/dependency);
  4. ease of stopping.

The relative dangers of each factor vary from drug to drug. For example, heroin is highly toxic acutely but may cause little chronic toxicity provided it is used in a sterile fashion. The benzodiazepines have relatively little acute toxicity but may be difficult to stop taking after long-term use.

Acute toxicity

  1. The acute toxicity of a drug determines the risk of death or severe and immediate symptoms following an overdose. Data on the lethal dose that kills 50% of individuals exposed to it (LD50) is available for all illicit drugs expressed as units of the drug per kilogram of body weight on the basis of experiments on animals. It is obviously more difficult to estimate the absolute value of the LD50 dose for humans. In terms of units of drug per kilogram of body weight it is probably much lower in humans than in animals, although the same rank order of lethality probably applies as with animals. On the basis of such data it is clear that the risk of overdose is highest for heroin, other opiates and cocaine – all more dangerous than alcohol in this respect. It is lowest for cannabis. Amphetamines, ecstasy, psychedelic drugs and benzodiazepines come somewhere in between.
  2. It is also possible to evaluate the safety of drugs indirectly through estimates of mortality rates in the population of users. Although the results are subject to considerable measurement errors, particularly in estimating the number of users, they can give an idea of the relative risks of dying after drug use. We discuss the implications for ecstasy in particular in paragraphs 29 and 30 below.

Chronic health risks

  1. This is harder to gauge, especially with drugs that have only recently become popular. More objective measures include mortality and morbidity statistics; less objective ones are clinical expert opinions. The safety approach used by drug regulatory authorities before licensing drugs for clinical use relies on the detection of pathological changes found after chronic administration in animals. Such studies have been done for many of the drugs controlled by the MDA, though not to our knowledge for cocaine, LSD or other psychedelics. On the basis of present knowledge, cannabis may lead in the long term to respiratory diseases in the same way as tobacco. Benzodiazepines present the lowest risks of long-term health damage and the stimulant drugs the highest. The emerging evidence about ecstasy is that it may cause more long-term damage than once supposed. The long-term risks of alcohol and tobacco, however, are also as high as from some illicit drugs. The psychedelic drugs (other than ecstasy) on present (limited) evidence carry fewer chronic health risks. This is an area that needs to be kept under continuing review in order to take account of advances in medical and scientific knowledge as they are made.

Route of use

  1. The route of use predicts the nature and severity of the physical damage that a drug can cause as well as its addictiveness. Intravenous use (injecting) dramatically increases the risk of infections when sterile needles and syringes are not available. Many regular intravenous drug users are hepatitis C positive and up to 20% of them will develop progressive destructive cirrhosis of the liver. A variable proportion are HIV positive and will be at high risk of developing AIDS. The exceptional speed of access that injecting gives to many body organs also results in increased risks of acute toxicity and overdose.
  2. Drugs which are readily injected are therefore more dangerous than others. They fall into four groups. The first of these comprises opiates, the second stimulants in liquid forms, including ampoules. Third are highly soluble drugs like buprenorphine that can easily be made into solutions from tablets. Finally there are less soluble drugs that are dissolved in solvents (as temazepam in gel capsule form) or temazepam and other benzodiazepines crushed and mixed with water.
  3. Other ways of taking drugs have their own risks if taken over a prolonged period. Smoking can lead to lung and heart disease, snorting and chewing to nose and mouth cancer. Even drugs that are swallowed (usually the safest method) may cause stomach cancer.

Dependence and addiction

  1. These terms overlap and are difficult to define. Both include a wide range of experiences and phenomena associated with problem drug use. Among them is the process of adaptation to drug use, known as tolerance, which results in the need to take ever larger doses of the drug to achieve the same effect. There may also be unpleasant and sometimes dangerous physical symptoms once the drug is stopped. These withdrawal symptoms are alleviated by taking the drug again. This relief use is a major reason for the continued use of certain drugs. The cycle of dependence becomes stronger the longer the use of the drug goes on.
  2. These forms of dependence are known as physical dependence and are associated with all the drugs controlled by the MDA with the possible exception of LSD, other psychedelics and ecstasy. Physical dependence may arise without tolerance and without increasing the dosage. This has been called normal dose dependence and is found particularly in the benzodiazepines. It is, however, hard to measure the severity of the withdrawal symptoms in such cases since they are often confused with the re-emergence of the symptoms of the disorders for which the drug was prescribed.
  3. Perhaps what most people understand by addiction is the need to keep on taking the drug for its pleasurable effects. The pleasure that a drug produces leads to the desire to use it again; the effect is called reinforcement. The degree of pleasure relates to the action of the drug on the brain’s chemical systems and varies with the chemical structure of drugs even within the same family. This is why heroin gives more pleasure than other opiates such as codeine or buprenorphine. The process by which drug dependence is achieved in this way is termed psychological dependence and in its extreme form is called craving.
  4. Physical and psychological dependence are both likely to be present to some extent in the careers of drug users. Research evidence suggests that early in a drug user’s career pleasure-seeking is the main motivation for continued use whereas later on the wish to avoid withdrawal symptoms predominates. The propensity of a drug to cause craving and the difficulty that users find in stopping are both therefore important indicators of risk. So is the ease with which the symptoms concerned are re-established if the drug is taken again after a period of abstinence.

Social risks

  1. Some forms of social harm are a direct consequence of intoxication, for example road traffic accidents. Others come from addiction and dependence: the drug controls behaviour to an extent that has detrimental effects on all aspects of social functioning. In severe cases this can lead to complete personal collapse with loss of job, family and ability to look after oneself. It may also lead to acquisitive crime in order to obtain the funds to buy further supplies of the drug. A third area relates to the medical complications and the costs of treating drug use and dependence.
  2. Social harm is hard to quantify. The health care impact is difficult to estimate because the costs of treating addiction are fixed arbitrarily by the availability of treatment resources. Also they are only a fraction of the full medical costs. Unknown extra costs include those due to accidents, infections and mental illness. Other social costs, for example from crime, are hard to measure because it may not always be the drug use that leads to the commission of criminal offences4. It is, however, possible to reach a reasoned assessment of relative social harm without precisely quantified estimates. The addictive and dependency potential of a drug can be used to a large extent as a proxy for the social risks - a highly addictive drug will lead to a great deal of social harm.
  3. Such evidence as there is suggests that the health and other social costs attributable to illicit drugs are small compared with the health and social costs of alcohol and tobacco. A recent French study5 has estimated that 6% of the costs of responding to social problems caused by drugs are attributable to illicit drugs as compared with 40% to tobacco and 54% to alcohol.

Our assessment of the relative harms of drugs

  1. We have sought to rank controlled drugs on the basis of the available pharmacological and other evidence of each drug’s likelihood of causing the following physical and social problems: i) acute (i.e. immediate) physical harm, including the risk of overdose; ii) physical harm from chronic (i.e. longer-term) use; iii) ease with which drug may be injected; iv) likelihood of drug leading to dependence and addiction; v) physical withdrawal symptoms; vi) psychological withdrawal symptoms; vii) risk of social harm through intoxication; viii) risk of causing other social problems; ix) risk of medical costs arising.
  2. We consulted the members of the Royal College of Psychiatrists’ Faculty of Substance Misuse about the relative harmfulness of controlled drugs. We received replies from 29 out of 77 of them. Although we did not ask them specifically how they would classify the drugs concerned, their replies showed a high degree of consensus over the ranking of drugs by harmfulness. No-one disputes the position of heroin and cocaine at the top of the list. Methadone, amphetamines, barbiturates and temazepam when used intravenously are, in the consensus view of those whom we consulted, in the top seven (as is alcohol). Ecstasy, LSD, steroids and cannabis come in the last five (below tobacco). Buprenorphine, codeine and benzodiazepines other than temazepam are in-between.
  3. Assessing our results in the light of these responses seems to us to point to the following implications for the present Classes. To put things in perspective, we show in square brackets where alcohol and tobacco might come in the Classes if they were drugs controlled under the MDA.

Main drugs and their Classes

Class A

other opiates in pure form
amphetamines in injectable form

Class B

amphetamines other than injectable
ecstasy and ecstasy-type drugs

Class C

cannabinol and cannabinol derivatives

Our conclusions on classification

Number of Classes

  1. We have considered whether three Classes of drug are still appropriate. One advantage of doing away with Classes altogether would be that attention would focus on the offences themselves irrespective of the drug concerned. Reducing the number of Classes to two on the other hand would enable a clear division to be opened up between the seriously dangerous and the less harmful drugs. This is the approach of the Netherlands, where heroin, cocaine, amphetamines, ecstasy and other drugs described as posing unacceptable risks are on one list while a second list contains cannabis, most barbiturates and most tranquillisers.
  2. We are not inclined to abolish the Classes altogether. We consider that the differences between drugs are important, and need to be credibly reflected in our law if penalties are to be proportionate to a drug’s harm. We are impressed with the Netherlands’ determination to draw a clear and meaningful distinction between dangerous and less harmful drugs; but we doubt whether it accurately reflects the complexity of the situation. The Netherlands claims, with considerable justification, to have created clear blue water between cannabis and heroin. We doubt whether they can make the same claim in respect of other drugs, especially ecstasy, which are widely used in the Netherlands. These seem to us to be in a position intermediate between the highly dangerous and addictive drugs like heroin and the less harmful ones like cannabis. The model of three Classes offered by the MDA enables this to be reflected and we therefore believe that it should be retained.
  3. In recommending the retention of three Classes, we also recommend the transfer of certain drugs between Classes in accordance with the analysis in paragraphs 7 to 24 above. We further propose clear criteria for the future to govern additions to and transfers between the Classes.

Transfers of drugs between Classes

  1. The analysis above demonstrates in our view the extent to which the MDA’s Classes fail to reflect the most up-to-date medical and scientific knowledge.
  1. The evidence for the association between drugs and crime is assembled in Drug-driven Crime: A factual and statistical analysis. London, NACRO 1999, and discussed further in this report in Chapters Two (paragraphs 5 and 6), Seven (paragraph 19) and Eight (paragraphs 2 to 9 and 14).
  2. P. Kopp, Le Cout Social des Drogues Licites (Alcool et Tabac) et Illicites, Paris, OFDT and MILDT 1999.