Opioid poisoning (Opiate overdose) is a life-threatening toxicological emergency caused by excessive stimulation of opioid receptors — primarily µ-opioid receptors in the brainstem respiratory centers. The most dangerous effect is respiratory depression leading to hypoxia, coma and death.

Poisoning may occur at any age:

• Neonates — maternal opioid exposure

• Children — accidental ingestion

• Adults — therapeutic error, substance misuse

• Palliative care — dosing accumulation

Common causative agents include:

• Codeine

• Dihydrocodeine

• Morphine

• Heroin

• Methadone

• Tramadol

• Fentanyl

• Loperamide (high dose misuse)

• Opium preparations

• Diamorphine

Polysubstance ingestion (opioids + alcohol/benzodiazepines) greatly increases mortality risk.

2. Pathophysiology

Opioids bind to central nervous system receptors:

Major lethal mechanism:suppression of medullary respiratory center → CO₂ retention → hypoxia → cardiac arrest

Additional effects:

• Reduced gastrointestinal motility

• Reduced sympathetic tone

• Increased vagal tone

• Pulmonary edema

• CNS depression

3. Risk Factors

• Substance use disorder

• Previous overdose

• Recent detoxification (loss of tolerance)

• Concurrent alcohol or sedatives

• Chronic lung disease

• Chronic kidney disease (drug accumulation)

• Elderly age

• Neonates born to opioid-using mothers

• High potency synthetic opioids (fentanyl analogues)

• Social disadvantage and homelessness

4. Clinical Features

Classic Opioid Toxidrome (Triad)

1. Depressed consciousness

2. Pinpoint pupils (miosis)

3. Respiratory depression

Acute Toxicity

Neurological

• Drowsiness

• Confusion

• Slurred speech

• Coma

Respiratory

• Bradypnea (<12/min)

• Shallow breathing

• Cyanosis

• Apnoea

Gastrointestinal

• Nausea

• Vomiting

Cardiovascular

• Hypotension

• Bradycardia (occasionally tachycardia)

• Shock in severe cases

Pupils

• Pinpoint pupils (may dilate in severe hypoxia)

Chronic Toxicity / Dependence

• Constipation

• Anorexia

• Nausea

• Endocrine suppression

• Tolerance

• Withdrawal on cessation

Neonatal Opioid Toxicity

• Poor feeding

• Respiratory depression

• Hypotonia

• Apnoea

5. Diagnostic Criteria

Diagnosis is primarily clinical.

Suspect opioid poisoning in any patient with:

• Altered consciousness

• Hypoventilation

• Pinpoint pupils

Response to naloxone confirms diagnosis.

6. Investigations

Bedside

• Pulse oximetry

• Capillary glucose (exclude hypoglycemia)

• Arterial blood gas (respiratory acidosis)

Laboratory

• Serum electrolytes

• Renal function tests

• Toxicology screen

• Serum drug levels (if available)

Imaging

• Chest X-ray — aspiration pneumonia / pulmonary edema

• CT brain if diagnosis uncertain

7. Management

Treat immediately — do NOT wait for lab confirmation

7.1 Initial Resuscitation (ABCDE)

Airway

• Position airway

• Remove secretions

• Intubate if airway unprotected

Breathing

• Oxygen 10–15 L/min

• Assist ventilation with bag-valve mask

Circulation

• IV access

• Monitor ECG

• Treat hypotension with fluids

7.2 Antidote Therapy — Naloxone

Naloxone is a competitive opioid antagonist with rapid onset (1–2 minutes IV).

Hypoventilating patient (spontaneous breathing)

Adults & Children >20 kg

Initial:0.5 mg IV

Titrate every 2–3 minutes until RR ≥ 12/min

Children <20 kg

0.01 mg/kg IV(Max 2 mg/dose)

Apnoea

Neonates (maternal opioid exposure)

0.01 mg/kg IV/IM(Max 0.4 mg/dose)

Children <20 kg

0.1 mg/kg IV(Max 2 mg/dose)

Repeat or infusion if needed

Adults / >20 kg

2 mg IVRepeat every 3 minutes up to 10 mg total

If no response → consider other diagnosis

Continuous Infusion

Required for long-acting opioids (e.g. methadone)

Dose:2/3 effective reversal dose per hour

Important Warning

Rapid reversal may cause:

• Severe withdrawal

• Pulmonary edema

• Cardiac arrhythmia

Use lowest effective dose especially in neonates.

7.3 Supportive Care

• Cardiac monitoring

• Observe minimum 6–24 hours (longer for methadone)

• Prevent aspiration

• Treat pulmonary edema

• Manage withdrawal if occurs

8. Complications

• Hypoxic brain injury

• Aspiration pneumonia

• Acute respiratory distress syndrome

• Rhabdomyolysis

• Death

9. Prevention

Do’s

• Store medicines safely

• Child-resistant containers

• Read labels carefully

Don’ts

• Transfer medications

• Leave containers open

• Call medicine sweets

• Take drugs in front of children

Public Health Measures

• Opioid prescribing control

• Addiction treatment programs

• Take-home naloxone programs

• Patient education

10. Prognosis