Related Subjects:
|Drug Toxicity - clinical assessment
|Sedation and Analgesia on ITU
|Neuropathic Pain Management
|Codeine
|Dihydrocodeine
|Diamorphine
|Morphine
|Paracetamol (Acetaminophen)
|Tramadol
|Toxin elimination by dialysis
|Drug Toxicity with Specific Antidotes
|Naloxone (Narcan) Opiate antagonist
⚠️ Opioid toxicity presents with the classic triad: reduced GCS, respiratory depression, and pinpoint pupils.
💉 Naloxone reverses these effects but can precipitate acute withdrawal (yawning, vomiting, diarrhoea, myalgia).
🌅 In end-of-life care, use very small doses to relieve toxicity without abolishing analgesia.
📖 About
- Opioids are widely used for analgesia but also misused recreationally. Overdose is a frequent cause of medical emergency and death.
- Naloxone is an opioid receptor antagonist and is the antidote for opioid-induced respiratory depression.
- Overdose may be accidental (tolerance changes, drug interactions) or deliberate.
🧪 Aetiology & Pharmacology
- Opioids bind predominantly to mu (μ) receptors, producing analgesia, sedation, and respiratory depression. Kappa (κ) receptors contribute to analgesia and dysphoria.
- Risk ↑ with polypharmacy (alcohol, benzodiazepines, gabapentinoids).
💊 Common Opioids
- Heroin / Diamorphine
- Morphine
- Methadone
- Codeine / Dihydrocodeine
- Oxycodone
- Pethidine
- Coproxamol (paracetamol + dextropropoxyphene)
🧠 Clinical Presentation
- 😴 Depressed consciousness, drowsiness → coma.
- 🫁 Respiratory depression (slow, shallow breathing).
- 👁️ Pinpoint pupils (classic but may be absent if co-ingestants present).
- 💔 Bradycardia, hypotension; arrhythmias with some opioids (esp. dextropropoxyphene).
- 💉 Needle marks in habitual users.
- 🍷 Co-ingestion with alcohol or benzodiazepines worsens sedation.
🔬 Investigations
- 🧪 U&E, LFTs, glucose, lactate, ABG.
- 📈 ECG: arrhythmias, QRS widening (esp. with dextropropoxyphene).
- 🩸 Screen for paracetamol/salicylate co-ingestion.
- 📷 CXR: aspiration, pulmonary oedema, or pneumonia if suspected.
- 🧠 CT head if cause of ↓GCS remains unclear.
💉 Management
- 🛑 ABCs: ensure airway protection, give high-flow oxygen (15 L/min), support ventilation if needed.
- 💧 Treat non-cardiogenic pulmonary oedema with O₂ ± CPAP; diuretics if cardiogenic.
- 💉 Naloxone: start with 400 mcg IV; repeat every 2–3 min up to 2 mg if no response.
– If effective but opioid has longer half-life (e.g. methadone), consider IV infusion titrated to respiratory rate.
– In palliative patients, use very small doses (40–80 mcg) to avoid loss of analgesia.
- ⏳ Monitor closely - rebound sedation likely once naloxone wears off.
- Alternative routes: IM, SC, or intranasal if IV access is delayed.
- 👥 Admit all deliberate overdoses for psychiatric assessment once medically stable.
⚠️ Complications of Reversal
- Precipitated withdrawal: agitation, yawning, sweating, diarrhoea, myalgia.
- Rare but serious: hypertension, arrhythmias, pulmonary oedema, cardiac arrest (esp. with high bolus doses).
📚 References
