Home > Opioid misuse.

[Irish Medical Times] , Pinjon, Emmanuelle Opioid misuse. (02 Dec 2010)

External website: http://www.imt.ie/mims/2010/12/opioid-misuse.html

The term ‘opioids’ refers to a class of psychoactive substances derived from the poppy plant (including opium, morphine and codeine), as well as semi-synthetic forms (including heroin) and synthetic compounds (including methadone and buprenorphine) with similar properties. Illicit use of opioids generally involves injecting, or inhaling the fumes produced by heating the drug.

Opioids have many effects on the brain, mediated through specific receptors. The key opioid receptor subtype is μ, which mediates euphoria, as well as respiratory depression, and is the main target for opioids while the κ receptor is involved in mood regulation. Soon after injection (or inhalation), heroin metabolises into morphine and binds to opioid receptors. This is subjectively experienced as a euphoric rush, normally accompanied by a warm flush, dry mouth, and sometimes nausea, vomiting and severe itching. As the rush wears off, drowsiness, and slowing of cardiac function and breathing (sometimes to the point of death in an overdose), persist for several hours. The effects of methadone are similar but more drawn out and therefore less intense.

Drug misuse is a relapsing and remitting condition often involving numerous treatment episodes over several years. Drug misuse has a negative impact on health or functioning and may take the form of drug dependence, or be part of a wider spectrum of problematic or harmful behaviour. Many people who misuse opioids also misuse a range of other substances concurrently and regularly. Alcohol misuse is also common in people who misuse drugs.

The WHO ICD-10 Classification of Mental and Behavioural Disorders defines six criteria for substance use dependence. Dependence is diagnosed if three or more of these criteria have been experienced or exhibited together at some time during the previous year:
• Strong desire or compulsion to take a substance
• Difficulty in controlling substance use
• Presence of a physiological withdrawal state
• Tolerance of the use of the drug (increased doses are needed to achieve effects originally produced by lower doses)
• Neglect of alternative pleasures and interests
• Persistent use of the drug, despite harm to oneself and others

While the initiation of drug use does not lead inevitably to dependence over the long term, a number of factors can potentiate this developmental course. Earlier initiation of drug use increases the likelihood of daily use, which in turn results in a greater likelihood of dependence.....


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