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The opioid system and addiction 

The opioid system and addiction
The opioid system and addiction

David J. Nutt

and Liam J. Nestor

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date: 13 June 2021

The opioid system of the brain is the major target for opiate drugs such as morphine and heroin, and has been implicated in processes such as pain, stress and reward. Many of these effects take place at the mu opioid receptor (mOR), which is distributed throughout the brain. Significantly, genetic polymorphisms at the mOR may confer a greater dopamine response to the reinforcing effects of alcohol, and it has been suggested that addiction per se may be associated with alterations to the opioid system. There is evidence for the potential efficacy of mOR antagonists (e.g. naltrexone) in reducing drug and alcohol relapse, increasing treatment retention and attenuating the subjective effects of substances of abuse. Medications with partial agonist activity at the kappa opioid receptor (e.g. nalmefene) may also confer an additional clinical advantage by reducing binging following relapse.

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