Assessment and Management of Opioid Use Disorder, Withdrawal, and Intoxication Syndromes
Neurobiology of Opioid Dependence and withdrawal
Opioids act at specific opioid receptors in the central nervous system. Stimulation of these receptors suppresses the firing rate of noradrenergic neurons in the midbrain, thus causing CNS depression and reduction of anxiety. Euphoria is also because of the release of dopamine at nucleus coeruleus in the forebrain by dopaminergic neurons that originate in the ventral tegmental area in the midbrain. Opioid use causes reinforcement of the drug-taking behaviours because of these euphoric effects and the relief from anxiety. Repeated usage also causes neuroadaptive changes in these neurons, such that progressively less dopamine release in the nucleus coeruleus and less suppression of midbrain noradrenergic cells lead to reduced effects or increased doses being taken by the person (tolerance). When the person stops taking the drug, overexcited noradrenergic neurons in the midbrain give rise to the characteristic withdrawal symptoms of opioids.
Interventions for Opioid use Disorders
Formal psychosocial interventions
- Group-based psychoeducational interventions
- Information and advice
- Opportunistic brief interventions
- Contingency management
- Cognitive-behavioural therapy and psychodynamic therapy
- Interventions to improve concordance with naltrexone
Methadone for heroin dependence and withdrawal treatment
Methadone is a long-acting opiate agonist; its withdrawal begins after 36 hours; by this time heroin withdrawal has already peaked. Because of this, the symptoms of methadone withdrawal are milder. Long half-life also makes it less likely to make a user depend on it (remember withdrawal or the use of the drug to prevent withdrawal symptoms are part of the dependence syndrome).
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