Makindo Medical Notes

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

• NHS GGC: Opioid Toxicity Management
• TOXBASE (UK National Poisons Information Service)