opioid poisioning
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Opioid Poisoning
Epidemiology
Opioid poisoning is a major public health crisis. In 2022, the CDC reported that 89.1% of all fatal drug overdoses involved at least one opioid, accounting for ~41,744 deaths in the US. Opioid overdose became the leading cause of unintentional injurious death in people aged 25-60 years in the US - surpassing motor vehicle collisions. From 1999-2016, there was an approximate threefold rise in pediatric opioid poisoning mortality.
(Miller's Anesthesia, 10e; Rosen's Emergency Medicine)
Pathophysiology
Opioids act primarily on mu (μ), kappa (κ), and delta (δ) receptors in the CNS and periphery. In overdose:
- Mu-receptor activation causes respiratory depression (the primary cause of death), sedation, euphoria, and miosis
- CNS depression leads to loss of protective airway reflexes
- Peripheral effects include reduced GI motility, hypotension, and bradycardia
Death from overdose is almost always from respiratory failure - progressive hypoxia leads to cardiac arrest.
(Goodman & Gilman's Pharmacological Basis of Therapeutics)
The Classic Triad (Toxidrome)
| Feature | Detail |
|---|---|
| Coma / CNS depression | Drowsiness to deep coma |
| Pinpoint pupils (miosis) | Bilateral, except with meperidine, severe hypoxia/acidosis, or seizures |
| Respiratory depression | Very low rate or apnea; the essential finding |
Additional findings: cold/clammy skin, low body temperature, flaccid skeletal muscles, jaw relaxation (tongue may occlude airway), hypotension, bradycardia, and cyanosis. Convulsions may occur in infants/children.
(Goodman & Gilman's; Rosen's Emergency Medicine)
Differential Diagnosis
The opioid toxidrome can be mimicked by:
- Clonidine/guanfacine/tetrahydrozoline poisoning
- Valproic acid, gamma-hydroxybutyrate (GHB)
- Ethanol, sedative-hypnotics, atypical antipsychotics
- Pontine stroke or hemorrhage (non-toxicological)
A rapid response to naloxone is one of the two most important diagnostic clues (along with the clinical toxidrome). No laboratory test or drug screen should be relied upon to confirm the diagnosis.
(Rosen's Emergency Medicine)
Special Properties of Specific Opioids
| Effect | Opioid |
|---|---|
| QRS widening (Na⁺ channel blockade) | Propoxyphene (withdrawn from market) |
| QTc prolongation (K⁺ / hERG blockade) | Methadone |
| Seizures | Propoxyphene, meperidine, tramadol |
| Serotonin syndrome | Meperidine, methadone, tramadol, fentanyl |
| Ototoxicity / sensorineural hearing loss | Methadone, hydrocodone, heroin |
| Spongiform leukoencephalopathy, Parkinsonism | Heroin vapor ("chasing the dragon") |
(Rosen's Emergency Medicine)
Diagnostic Workup
- Point-of-care blood glucose - mandatory to exclude hypoglycemia mimicking opioid poisoning
- ECG - required for known/suspected methadone overdose (QTc); also for propoxyphene (QRS)
- Urine drug screen - unreliable; many synthetic opioids (oxycodone, methadone, fentanyl) are NOT detected on standard immunoassay screens. A negative screen does NOT rule out opioid poisoning
- EtCO₂ (end-tidal CO₂) monitoring - more sensitive for hypopnea, bradypnea, and apnea than pulse oximetry
- Chest X-ray - if pulmonary rales are present (aspiration, non-cardiogenic pulmonary edema)
(Washington Manual of Medical Therapeutics; Rosen's Emergency Medicine)
Management
1. Airway and Ventilation (First Priority)
- Establish a patent airway - jaw thrust, positioning
- Bag-valve mask ventilation may be required prior to or while waiting for naloxone to act
- Endotracheal intubation is rarely needed in isolated opioid poisoning (reversed by naloxone) but may be necessary in polysubstance overdose, major trauma, or co-existing illness
2. Naloxone - The Antidote
Naloxone is a competitive mu-opioid antagonist. It is the definitive antidote.
| Route | Situation |
|---|---|
| IV | Preferred in ED setting; fastest onset |
| IM / SC | If no IV access |
| Intranasal (Narcan® 4 mg) | Community/lay responder use; FDA approved |
| Endotracheal / Intraosseous | If no other access available |
Note: Naloxone is not effective orally due to near-complete first-pass hepatic metabolism.
Dosing principles:
- Goal: restore adequate respiration, NOT full wakefulness
- Typical starting dose: 0.04 mg IV (titrated up), repeated every 2-3 minutes as needed
- Arrest/near-arrest: start at 0.4-4.0 mg IV
- Buprenorphine, fentanyl, and other high-affinity agonists require higher doses (up to 10 mg may be needed)
- Patient who does not respond to 10 mg naloxone - question the diagnosis
- Opioid-dependent patients: use the lowest effective dose to avoid precipitating acute withdrawal (start 0.04 mg IV)
- Long-acting opioids (methadone, extended-release preparations): naloxone infusion is required, typically started at two-thirds of the effective reversal dose per hour
- Naloxone half-life is ~1 hour, shorter than most opioid agonists - re-narcotization/coma can occur after the naloxone wears off
Adverse effects of naloxone:
- Precipitates acute opioid withdrawal in dependent patients (diarrhea, hypertension, tachycardia, pain)
- "Overshoot" phenomenon - respiratory rate may transiently exceed baseline
- Rebound catecholamine release can cause hypertension, tachycardia, ventricular arrhythmias
- Pulmonary edema has been reported
(Goodman & Gilman's; Washington Manual; Rosen's Emergency Medicine; Miller's Anesthesia)
3. Decontamination
- Activated charcoal - not routinely recommended (risk of aspiration in sedated patient); consider on a case-by-case basis
- Gastric lavage - not recommended; risks outweigh benefits
- Whole bowel irrigation - may be considered for body packers (those with internally concealed drug packages)
4. Enhanced Elimination
- Most opioids have a large volume of distribution - no clinically effective techniques for extracorporeal elimination
Disposition and Observation
- After naloxone administration, the observation period depends on the opioid involved
- Overdoses with long-acting opioids or sustained-release preparations require longer observation
- Patients who respond and remain stable for 1-2 hours after short-acting opioid exposure may be candidates for discharge with appropriate follow-up
- All survivors should be offered medication for opioid use disorder (mOUD): methadone or buprenorphine - these reduce relapse, overdose, and premature death
(Rosen's Emergency Medicine; Washington Manual of Medical Therapeutics)
AHA BLS Recommendation (2020)
For patients with known or suspected opioid poisoning who are unresponsive with no normal breathing but have a pulse, appropriately trained lay rescuers and BLS providers should administer IM or IN naloxone in addition to standard BLS care.
(Miller's Anesthesia, 10e)
Key references:
- Rosen's Emergency Medicine: Concepts and Clinical Practice (9780323757898)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics (9781264258079)
- The Washington Manual of Medical Therapeutics (9781975190620)
- Miller's Anesthesia, 10e (9780323935920)
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