Last updated on: August 25th, 2021

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Opioid intoxication

Clinicals - History


Opioid intoxication is notorious for causing sedation. This is due to a reduction in central nervous system activity via opioid receptor binding.

Respiratory depression

In excessive amounts, opioids can cause respiratory depression which can be life-threatening. This is due to the activation of opioid receptors on neurons in the respiratory centers of the brainstem, and can be lethal.


Repeated use of opioids leads to neurochemical changes in the brain. Among these changes is the reduced responsiveness of opioid receptors to incoming opioids, resulting in greater opioid doses needed to stimulate the reward system of the brain. This translates clinically into tolerance, a physiological need for higher opioid doses to achieve the same effect.

Physical dependence

Physical dependence occurs when a person who has developed tolerance, or become used to higher opioid doses, no longer has access to the drug and therefore experiences physiological symptoms of a lack of drug use. Withdrawal symptoms can increase the patient's dependence, drug-seeking and addictive behaviors as the patient attempts to avoid these symptoms.

Increased drug seeking behavior

Acute opioid intoxication is often preceded by stronger attempts to obtain higher doses of opioids to achieve both pain relief and euphoria. This is due to the individual having developed tolerance and physical dependence on the drug. Opiates sought can be either prescription or illicit.

Psychiatric co-morbidities

Mental illness has been associated both directly and indirectly with both chronic pain and opioid use. These are specifically linked through a "negative affect" syndrome comprising a cluster of recurrent negative emotions and thoughts and related anxiety, depression and a catastrophizing cognitive style. Post-traumatic stress disorder has also been implicated. This negative affect syndrome is related to poor outcomes with chronic pain and increased opioid use.

Psychosocial risk factors

Multiple psychosocial factors have been linked to opioid use disorder and risk of opioid intoxication. These include problems with social groups and community, history of childhood trauma, involvement in criminal activity, high economic burdens and intimate partner violence.

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