Opioid Poisoning (Overdose)

Pathophysiology

Clinical Features — The Classic Triad

Diagnosis

• Clinical — recognition of the triad is the basis for immediate treatment; do not wait for labs.
• Toxicology screen (blood or urine) confirms the diagnosis but must not delay management.
• Consider co-ingestion: benzodiazepines are a frequent fatal combination (especially with buprenorphine).

Emergency Management

Step 1 — Airway & Breathing

• Establish airway immediately; intubation and mechanical ventilation may be required.
• Supplemental oxygen; bag-mask ventilation if needed.

Step 2 — Naloxone (Opioid Antagonist)

• Repeat doses as needed to restore adequate respiration.
• Continuous IV infusion: give ½ to ⅔ of the initial reversal dose per hour; titrate to respiratory rate — not to consciousness (avoid precipitating withdrawal).
• Duration: naloxone infusion typically continued 24–72 hours depending on the opioid (morphine vs. long-acting methadone).

• Fentanyl / high-potency synthetic opioids: may require total doses ≥10 mg naloxone; rescue kits designed for fentanyl contain double the traditional dose.
• Buprenorphine overdose: primary buprenorphine overdose alone is nearly impossible due to its partial agonist ceiling effect; suspect co-ingestion (especially benzodiazepines).
• Nalmefene — higher potency, longer duration than naloxone; now available as an alternative reversal agent.

Naloxone administration flowchart — The Maudsley Prescribing Guidelines, 15th ed.

Co-ingestion / Mixed Overdose

Summary Table: Management of Opioid Overdose

1. Establish airway; intubation + mechanical ventilation if necessary
2. Naloxone 0.4–2.0 mg IV/IM/ET — onset ~1–2 min
3. Repeat doses as needed, then continuous infusion (½–⅔ of reversal dose/hour)
4. Continuous monitoring for 24–72 h; infusion not needed if patient is intubated
5. Consider co-ingestants if response is partial

Post-Acute: Withdrawal & Longer-Term Treatment

Opioid Withdrawal Management

FDA-Approved Treatments for Opioid Use Disorder

Take-Home Naloxone (Prevention)

• Patients on >50 morphine milligram equivalents/day should receive a naloxone prescription at discharge.
• IM or intranasal naloxone kits are effective for lay first-responders.
• Patient and family training in take-home naloxone significantly reduces overdose deaths. — Washington Manual; Maudsley Guidelines

Pontine Hemorrhage vs. Opioid Poisoning

Why They Overlap

1. Descending sympathetic pupillodilator fibres (sympathetic, from hypothalamus)
2. Ascending pupillodilator pathways

Side-by-Side Comparison

The Decisive Distinguishing Features

1. Ocular Bobbing

2. Absent Oculovestibular Responses

3. Quadriplegia / Decerebrate Posturing

4. Hyperthermia vs. Hypothermia

5. Naloxone Test

"The pinpoint pupils may suggest an opiate overdose, but the other eye signs and flaccid quadriplegia are not seen in that condition. If there is any question in an ambiguous case, naloxone can be administered to reverse any opiate intoxication." — Plum and Posner's Diagnosis and Treatment of Stupor and Coma

CT Scan

CT showing large tegmental-basal pontine hemorrhage with temporal horn hydrocephalus — Bradley and Daroff's Neurology in Clinical Practice

Clinical Findings in Pontine Hemorrhage (n=80)

Quick Decision Algorithm

Coma + Pinpoint Pupils
        │
        ├── Give IV Naloxone 0.4–2 mg
        │         │
        │    Reversal → Opioid Poisoning ✓
        │    No reversal ↓
        │
        ├── CT Head (stat, non-contrast)
        │         │
        │    Hyperdense pontine lesion → Pontine Hemorrhage ✓
        │    Normal CT ↓
        │
        └── Metabolic / toxic workup (BMP, LFTs, toxicology, EEG)