Refraining from drug use. A person taking prescribed methadone but no illicit opioids would still be described as abstinent. The term “abstinence” should not be confused with the term “abstinence syndrome”, which refers to withdrawal syndrome.

Treatment of drug dependence by prescribing a substitute drug to which the patient is cross-dependent and cross-tolerant. Examples of agonist maintenance therapies are methadone and buprenorphine to treat heroin dependence, and nicotine gum to replace tobacco smoking. The goals of agonist maintenance therapy are to eliminate or reduce use of a particular substance (especially if it is illegal), reduce the harm and health risks of a particular method of substance administration (e.g. risk of disease from needle-sharing) and reduce the social consequences of drug dependence. Agonist maintenance therapy can last from several months to more than 20 years, and is often accompanied by other treatment (e.g. psychosocial treatment). It is sometimes distinguished from tapering-off therapy. (See opioid withdrawal syndrome.)

Diseases such as HIV and hepatitis B and C, which are spread by blood-to-blood contact (e.g. needle sharing).

The Convention on Psychotropic Substances, 1971 is the second of the international drug control treaties, supplementing the Single Convention on Narcotic Drugs, 1961. It aims to control psychotropic substances, as defined under this convention, and to prevent their abuse. The Convention outlines a number of responsibilities for parties. The International Narcotics Control Board (INCB), which submits its reports to the Economic and Social Council (ECOSOC) through the Commission on Narcotics Drugs (CND) is responsible for monitoring the compliance by governments with the 1971 Convention, ensuring on the one hand that psychotropic substances are available for medical and scientific use, and on the other hand that diversion from licit sources to illicit traffic does not occur. Buprenorphine is listed in the Convention on Psychotropic Substances.

As a general term, the state of needing or depending on something or someone for support or to function or survive. As applied to opioids, implies the need for repeated doses of a drug to feel good or to avoid feeling bad.

In 1964, a World Health Organization (WHO) Expert Committee introduced the term “dependence” to replace addiction and habituation. The term can generally be used with reference to dependence on any psychoactive drugs (e.g. drug dependence, chemical dependence, substance dependence), or with specific reference to a particular drug or class of drugs (e.g. opioid dependence). Although ICD-10 has a specific definition for dependence, described in terms applicable across drug classes, the symptoms of dependence will vary for each specific drug.

Dependence often refers to both the physical and psychological elements of drug dependence. More specifically, psychological or psychic dependence refers to the experience of impaired control over drug use (including cravings and compulsions to use drugs) while physiological or physical dependence refers to tolerance and withdrawal symptoms (see neuroadaptation). However, in biologically oriented discussion, dependence is often used to refer only to physical dependence.

Dependence or physical dependence is also used in a narrower sense in the psychopharmacological context, to refer solely to the development of withdrawal symptoms on cessation of drug use.

The process of an individual being withdrawn from the effects of a psychoactive substance. When referring to a clinical procedure, detoxification refers to a withdrawal process that is carried out in a safe and effective manner, minimizing the withdrawal symptoms. The facility where this takes place may be called a detoxification or “detox” centre.

In the context of alcohol or other drugs, harm reduction (or harm minimization) describes policies or programmes that focus directly on reducing the harm resulting from the use of alcohol or drugs. The term is used particularly to refer to policies or programmes that aim to reduce the harm without necessarily changing the underlying drug use; examples include needle and syringe exchanges to counteract needle sharing among heroin users, and self-inflating airbags in automobiles to reduce injury in accidents, particularly as a result of drink–driving. Harm-reduction strategies cover a wider range of activities than simple reduction of supply and demand.

A pattern of psychoactive substance use that is causing damage to health (ICD-10, code F11.1). The damage may be physical (e.g. in the cases of hepatitis from the self-administration of injected psychoactive substances) or mental. Harmful use often, but not always, has adverse social consequences; social consequences alone, however, are not sufficient to justify a diagnosis of harmful use.

The term was introduced in ICD-10 and replaced “non-dependent use” as a diagnostic term.

Narcotic drugs are the substances included in Schedules I and II of the Single Convention on Narcotic Drugs, 1961, (see below), whether natural or synthetic. Methadone is a narcotic drug.

The changes in neurones associated with both tolerance and the appearance of withdrawal syndrome. Individuals can exhibit neuroadaptation without showing the cognitive or behavioural manifestation of dependence. For example, surgical patients given opioid substances to relieve pain may sometimes experience withdrawal symptoms but may not recognize these symptoms or have any desire to continue taking drugs.

One of a group of alkaloids derived from the opium poppy (Papaver somniferum), with the ability to induce analgesia, euphoria, and, in higher doses, stupor, coma, and respiratory depression. The term excludes synthetic opioids.

The generic term applied to alkaloids from the opium poppy (Papaver somniferum), their synthetic analogues, and compounds synthesized in the body. All of these substances interact with the same specific receptors in the brain, have the capacity to relieve pain and produce a sense of well-being (euphoria). The opium alkaloids and their synthetic analogues also cause stupor, coma and respiratory depression in high doses.

Opium alkaloids and their semisynthetic derivatives include morphine, diacetylmorphine (diamorphine, heroin), hydromorphine, codeine and oxycodone. Synthetic opioids include levorphanol, propoxyphene, fentanyl, methadone, pethidine (meperidine) and the agonist–antagonist pentazocine. Endogenously occurring compounds with opioid actions include the endorphins and enkephalins.

The most commonly used opioids (such as morphine, heroin, hydromorphine, methadone and pethidine) bind preferentially to the μ-receptors; they produce analgesia, mood changes (e.g. euphoria, which may change to apathy or dysphoria), respiratory depression, drowsiness, psychomotor retardation, slurred speech and impaired concentration, memory and judgement.

Physical consequences of opioid use (mostly resulting from intravenous administration) include hepatitis B, hepatitis C, HIV, septicaemia, endocarditis (inflammation of the inner layer of the heart), pneumonia and lung abscess, thrombophlebitis (blood clots causing vein inflammation) and rhabdomyolysis (breakdown of muscle fibres). Psychological and social impairment is common, reflecting the illicit nature of non-medical opioid use.

Any of the naturally occurring brain neuropeptides, which include at least two major groups–the enkephalins and the endorphins. Both can interact with opiate-binding sites (receptors) and thus may modulate the perception of pain. Endorphins also appear to modulate mood and responses to stressful stimuli (see opioid).

A condition that follows the administration of opioids, resulting in disturbances in the level of consciousness, cognition, perception, judgement, affect, behaviour or other psychophysiological functions and responses. These disturbances are related to the acute pharmacological effects of, and learned responses to, opioids. With time, these disturbances resolve, resulting in complete recovery, except where tissue damage or other complications have arisen.

Intoxication depends on the type and dose of opioid, and is influenced by factors such as an individual's level of tolerance. Individuals often take drugs in the quantity required to achieve a desired degree of intoxication. Behaviour resulting from a given level of intoxication is strongly influenced by cultural and personal expectations about the effects of the drug.

Acute intoxication is the ICD-10 term for intoxication of clinical significance (F11.0). Complications may include trauma, inhalation of vomitus, delirium, coma and convulsions, depending on the substance and method of administration.

The use of opioids in amounts that produce acute adverse physical or mental effects. Deliberate overdose is a common method of suicide. In absolute numbers, overdoses of licit opioids tend to be more common than those of illicit opioids. Overdose may produce transient or lasting effects, or death; the lethal dose of a particular opioid varies with the individual and with circumstances.

A group of conditions associated with the use of opioids. In ICD-I0, section F11.0–9 (“Mental and behavioural disorders due to psychoactive substance use (opioids)”) contains a wide variety of disorders of different severity and clinical form, all having in common the use of opioids, which may or may not have been medically prescribed. The clinical states that may occur include acute intoxication, harmful use, dependence syndrome, withdrawal syndrome (or withdrawal state), withdrawal state with delirium, psychotic disorder, late-onset psychotic disorder and amnesic syndrome.

Over time, morphine and its analogues induce tolerance and neuroadaptive changes that are responsible for rebound hyperexcitability when the drug is withdrawn. The withdrawal syndrome includes craving, anxiety, dysphoria, yawning, sweating, piloerection (gooseflesh), lacrimation (excessive tear formation), rhinorrhoea (running nose), insomnia, nausea or vomiting, diarrhoea, cramps, muscle aches and fever. With short-acting drugs, such as morphine or heroin, withdrawal symptoms may appear within 8–12 hours of the last dose of the drug, reach a peak at 48–72 hours, and clear after 7–10 days. With longer acting drugs, such as methadone, onset of withdrawal symptoms may not occur until 1–3 days after the last dose; symptoms peak between the third and eighth day and may persist for several weeks, but are generally milder than those that follow morphine or heroin withdrawal after equivalent doses.

Any non-pharmacological intervention carried out in a therapeutic context at an individual, family or group level. Psychosocial interventions may include structured, professionally administered interventions (e.g. cognitive behaviour therapy or insight oriented psychotherapy) or non-professional interventions (e.g. self-help groups and non-pharmacological interventions from traditional healers).

Psychotropic substances are the substances, natural or synthetic, or any natural material in Schedules I, II, III or IV of the Convention on Psychotropic Substances, 1971, (see above). Among others, buprenorphine and benzodiazepines are psychotropic substances.

The Single Convention on Narcotic Drugs, 1961 (as amended by the 1972 Protocol) is the main international drug control treaty. Replacing a number of previous conventions, it aims to limit the cultivation, production, manufacture and use of narcotic drugs to medical and scientific purposes, while ensuring their availability for such purposes. The convention lists a number of narcotic drugs, and outlines the responsibilities of parties with regard to the production, manufacture, distribution and use of these drugs in their countries. The INCB, which submits its reports to ECOSOC through the CND, is responsible for monitoring the compliance of governments with the provisions of this treaty. Methadone is listed in the Single Convention on Narcotic Drugs, 1961.

A decrease in response to a drug dose that occurs with continued use. If an individual is tolerant to a drug, increased doses are required to achieve the effects originally produced by lower doses. Both physiological and psychosocial factors may contribute to the development of tolerance. Physiological factors include metabolic and functional tolerance. In metabolic tolerance, the body can eliminate the substance more readily, because the substance is metabolized at an increased rate. In functional tolerance, the central nervous system is less sensitive to the substance. An example of a psychosocial factor contributing to tolerance is behavioural tolerance, where learning or altered environmental constraints change the effect of the drug. Acute tolerance refers to rapid, temporary accommodation to the effect of a substance following a single dose. Reverse tolerance, also known as sensitization, refers to a condition where the response to a substance increases with repeated use. Tolerance is one of the criteria of the dependence syndrome.

A group of symptoms of variable clustering and degree of severity that occur on cessation or reduction of use of a psychoactive substance that has been taken repeatedly, usually for a prolonged period or in high doses (ICD-10 code F1x.3). Withdrawal syndrome may be accompanied by signs of physiological disturbance. It is one of the indicators of dependence syndrome, and is the defining characteristic of the psychopharmacological definition of dependence.

The onset and course of withdrawal syndrome are time limited and relate to the type of substance and dose being taken immediately before cessation or reduction of use. Typically, the features of withdrawal syndrome are the opposite of acute intoxication.

Opioid withdrawal is accompanied by rhinorrhoea (running nose), lacrimation (excessive tear formation), aching muscles, chills, piloerection (gooseflesh) and, after 24–48 hours, muscle and abdominal cramps. Drug-seeking behaviour is prominent and continues after the physical symptoms have abated.