Opioid Intoxication is a clinical condition resulting from recent opioid use causing clinically significant behavioural, psychological, and physiological changes due to opioid effects on the central nervous system.

Severe opioid intoxication may progress to respiratory depression, coma, and death due to suppression of the brainstem respiratory centres.

Epidemiology

• Opioid intoxication is a major cause of preventable overdose deaths worldwide

• Risk is increased among individuals using high opioid doses, injecting opioids, or combining opioids with alcohol or sedative medicines

• Opioid overdose is a significant public health concern due to its rapid progression and mortality risk

Risk Factors

• High opioid doses

• Recent increase in opioid dose

• Loss of tolerance after a period of abstinence

• Injection opioid use

• Combining opioids with alcohol or benzodiazepines

• Previous overdose history

• Respiratory disease

• Reduced access to overdose prevention measures

Pathophysiology

Opioids stimulate μ-opioid receptors in the central nervous system, producing analgesia, sedation, and respiratory depression. Excessive opioid stimulation suppresses respiratory drive, reduces consciousness, and causes life-threatening hypoxia. Opioids also stimulate gastrointestinal and autonomic pathways causing other clinical effects.

Clinical Presentation

Common Features

• Drowsiness

• Reduced level of consciousness

• Loss of consciousness

• Slurred speech

• Impaired attention or memory

• Pupillary constriction

Severe Overdose Features

• Slow or absent breathing

• Cyanosis

• Coma

• Hypotension

• Cardiac arrest

Note:

• Pupillary dilation may occur in severe overdose due to hypoxia or anoxia

Diagnostic Criteria (DSM-5)

Diagnosis requires:

• Recent opioid use

• Clinically significant problematic behavioural or psychological changes developing during or shortly after opioid use

The condition is characterized by:

• Pupillary constriction or pupillary dilation due to severe overdose-related hypoxia

And at least one of the following:

• Drowsiness or loss of consciousness

• Slurred speech

• Impairment in attention or memory

Symptoms should not be better explained by another medical condition or another substance.

Differential Diagnosis

• Alcohol intoxication

• Sedative-hypnotic intoxication

• Head injury

• Stroke

• Hypoglycaemia

• Seizure disorder

• Metabolic encephalopathy

Investigations

Laboratory Investigations

• Blood glucose

• Oxygen saturation monitoring

• Arterial blood gas where indicated

• Electrolytes

• Renal function tests

• Toxicology screening

• Urine drug screening where available

Additional Assessment

• Airway breathing and circulation assessment

• Assessment for trauma

• Electrocardiogram where indicated

Management

Treatment Goals

• Restore adequate breathing

• Reverse opioid effects

• Prevent death and complications

Non-Pharmacological Management

• Assess airway breathing and circulation immediately

• Provide oxygen support when required

• Assist ventilation if respiratory depression is present

• Monitor vital signs and consciousness level

• Place unconscious patients in a safe position

• Identify and manage associated injuries

• Observe for recurrent toxicity due to opioid duration exceeding naloxone effect

Pharmacological Management

Naloxone 0.04–15 mg intramuscularly or intravenously. If there is no response, increase the dose every 2 minutes until adequate respiratory response is achieved.

Notes:

• The goal is restoration of adequate breathing rather than complete reversal of all opioid effects

• Monitor closely because repeated doses or infusion may be required due to recurrence of opioid toxicity

• Observe patients after reversal because opioid effects may last longer than naloxone

Referral Criteria

Refer to the next level of care if:

• Severe respiratory depression

• Recurrent overdose

• Need for prolonged monitoring

• Suspected intentional overdose

• Coexisting psychiatric illness

• Opioid Use Disorder requiring treatment

• Complications requiring specialist care

Complications

• Respiratory failure

• Hypoxic brain injury

• Aspiration pneumonia

• Coma

• Cardiac arrest

• Death

• Recurrent overdose

Prevention

• Access to opioid dependence treatment

• Safe opioid prescribing practices

• Education on overdose risks

• Avoid combining opioids with alcohol or sedatives

• Availability of naloxone where appropriate

• Harm reduction programmes

Prognosis

Prompt recognition and administration of naloxone significantly improve outcomes. Delayed treatment may result in severe hypoxia, neurological injury, or death.

Patient Education

• Opioid overdose is a medical emergency requiring urgent treatment

• Avoid mixing opioids with alcohol or sedative medicines

• Take opioid medicines only as prescribed

• Individuals with repeated opioid intoxication should be assessed for Opioid Use Disorder

• Seek immediate medical help for reduced consciousness, slow breathing, or suspected overdose