Sedative/hypnotic toxicity

(Redirected from Hypnotics)

Background

  • Sedative-hypnotics are a broad class of CNS depressants that enhance GABAergic inhibition or otherwise suppress CNS activity[1]
  • Includes: benzodiazepines (most common), barbiturates, non-benzodiazepine receptor agonists ("Z-drugs": zolpidem, zaleplon, eszopiclone), GHB/GBL, chloral hydrate, meprobamate, and older agents (ethchlorvynol, glutethimide, methaqualone)
  • Sedative-hypnotics are among the most frequently reported drug classes in overdose-related ED visits[2]
  • Oral benzodiazepine overdose alone rarely causes significant morbidity or mortality; serious toxicity almost always involves co-ingestion (opioids, alcohol, other sedatives)[3]
  • Barbiturate overdose carries significantly higher mortality than benzodiazepine overdose due to a narrow therapeutic index and direct GABA receptor activation (vs. benzodiazepine allosteric modulation)
  • Death from sedative-hypnotic overdose is almost always from respiratory depression and subsequent cardiorespiratory collapse[1]

Agent-Specific Notes

  • Benzodiazepines: Allosteric positive modulators at GABA-A receptor; cannot maximally activate the receptor alone (ceiling effect) → relatively safe in isolated overdose
  • Barbiturates: Direct GABA-A receptor agonists at high doses; can maximally activate receptor → no ceiling effect → fatal respiratory depression in overdose
  • Z-drugs (zolpidem, zaleplon, eszopiclone): Selective GABA-A α1 subunit agonists; generally mild toxicity in overdose; more severe with co-ingestants
  • GHB/GBL: Acts on GABA-B and GHB receptors; rapid onset/offset; patients may cycle between deep coma and agitation; associated with bradycardia[4]
  • Chloral hydrate: Narrow therapeutic index; active metabolite trichloroethanol; cardiac sensitization to catecholamines → risk of dysrhythmias
  • Meprobamate: May form gastric concretions (bezoars) → prolonged absorption and delayed toxicity

Clinical Features

Sedative-Hypnotic Toxidrome

  • CNS depression: Drowsiness → stupor → coma (dose-dependent)
  • Respiratory depression: Hypoventilation, apnea — most common cause of death
  • Hypotension: Peripheral vasodilation, myocardial depression (especially barbiturates)
  • Hypothermia
  • Slurred speech, ataxia, nystagmus (in mild-to-moderate intoxication)
  • Pupils: Usually mid-position and reactive; may be disconjugate
  • Hyporeflexia to areflexia in severe cases
  • Skin: May see bullous skin lesions ("barb blisters") classically with barbiturates (but non-specific — seen with any prolonged immobility/coma)

Agent-Specific Features

  • GHB: Abrupt onset of deep coma → sudden arousal/agitation ("on/off" pattern); bradycardia; emesis; duration of effect typically 2–6 hours[4]
  • Chloral hydrate: Pear-like odor; cardiac dysrhythmias (especially ventricular); GI hemorrhage
  • Ethchlorvynol: Vinyl-like odor; prolonged coma; pulmonary edema (with IV use)
  • Glutethimide: Anticholinergic features (may distinguish from pure sedative-hypnotic toxidrome)
  • Meprobamate: Hypotension may be refractory due to bezoar formation and prolonged absorption

Differential Diagnosis

Sedative/hypnotic toxicity

Evaluation

Toxic Alcohols Anion/Osmolar Gaps

Substance Osmolar gap Metabolic acidosis Anion gap Ketones Ca Oxalate crystals Reduced vision Management
Ethanol + +/- (if ketoacidosis) +/- (if ketoacidosis) +/- - - Mainly supportive
Ethylene glycol + (early)* + + - + - Fomepizole, Thiamine, Pyridoxine, +/- Dialysis
Methanol + (early)* + + - - + Fomepizole or ethanol, Folinic acid/Folic acid, +/- Dialysis
Isopropyl alcohol + - - + (acetonemia without acidosis) - - Mainly supportive, +/- Dialysis if severe
Propylene glycol + + + (lactic acidosis) - - - D/C offending agent (e.g. IV lorazepam/diazepam), supportive, +/- Dialysis
  • Osmolar gap → Anion gap transition: For all toxic alcohols, the osmolar gap is elevated early (parent compound present) and decreases over time as the alcohol is metabolized into organic acid metabolites, which then produce an anion gap metabolic acidosis. A normal osmolar gap does NOT exclude toxic alcohol ingestion if presentation is delayed.
Key distinguishing features
  • Isopropyl alcohol: The only toxic alcohol that causes ketosis without metabolic acidosis (metabolized to acetone, not an organic acid)
  • Ethylene glycol: Ca oxalate crystals in urine + anion gap metabolic acidosis + renal failure
  • Methanol: Visual disturbances (blurred vision, "snowfield" vision, blindness) + anion gap metabolic acidosis + optic disc hyperemia on fundoscopy

Toxidrome Chart

Finding Cholinergic Anticholinergic Sympathomimetic Sympatholytic^ Sedative/Hypnotic
Example Organophosphates TCAs Cocaine Clonidine ETOH
Temp Nl Nl / ↑ Nl / ↑ Nl / ↓ Nl / ↓
RR Variable Nl / ↓ Variable Nl / ↓ Nl / ↓
HR Variable ↑ ↑ (sig) Nl / ↓ Nl / ↓
BP ↑ ↑ ↑ Nl / ↓ Nl / ↓
LOC Nl / Lethargic Nl, agitated, psychotic, comatose Nl, agitated, psychotic Nl, Lethargic, or Comatose Nl, Lethargic, or Comatose
Pupils Variable Mydriatic Mydriatic Nl / Miotic
Motor Fasciculations, Flacid Paralysis  Nl Nl / Agitated Nl
Skin Sweating (sig) Hot, dry Sweating Dry
Lungs Bronchospasm / rhinorrhea Nl Nl Nl
Bowel Sounds Hyperactive (SLUDGE) ↓ / Absent Nl / ↓ Nl / ↓
^Consider Sympatholytic when looking at Sedative OD or someone who doesn't respond to Narcan
Withdrawal from substances have the opposite effect

History

  • Time and quantity of ingestion(s) — assume co-ingestion until proven otherwise
  • Prescription medications, OTC drugs, recreational substances, alcohol use
  • Prior history of substance use, psychiatric history, suicidal intent
  • Chronic benzodiazepine or barbiturate use (important for risk of withdrawal with flumazenil)

Diagnostics

  • Fingerstick glucose — obtain immediately in all patients with altered mental status
  • ECG — evaluate for QTc prolongation (co-ingestants), bradycardia (GHB), dysrhythmias (chloral hydrate)
  • BMP/CMP — electrolytes, renal function, glucose, anion gap
  • CBC
  • ABG/VBG — assess for respiratory acidosis (hypoventilation) or metabolic acidosis (co-ingestant, lactate from hypoperfusion)
  • Serum ethanol level
  • Acetaminophen and salicylate levels — screen for co-ingestion in all intentional overdoses
  • Urine drug screen — has significant limitations:
    • Standard immunoassays detect only select benzodiazepines (typically those metabolized to oxazepam/nordiazepam); may miss many commonly used agents (lorazepam, clonazepam, alprazolam, midazolam)
    • Most barbiturates, Z-drugs, GHB, chloral hydrate, and meprobamate are NOT detected on standard UDS
    • A negative UDS does not exclude sedative-hypnotic toxicity[1]
  • Serum barbiturate level — obtain if barbiturate ingestion is suspected; phenobarbital levels correlate with toxicity (lethal range generally > 80–150 μg/mL)
  • Serum drug levels are not routinely available or clinically useful for most benzodiazepines, Z-drugs, or GHB
  • CXR — if aspiration is suspected
  • CT head — consider if altered mental status does not improve as expected, or if history is unreliable

Management

Resuscitation / Supportive Care

  • Airway: This is the priority; intubate for inability to protect airway, severe respiratory depression, or refractory hypoxia[1]
  • Breathing: Supplemental O2; monitor closely for hypoventilation; bag-valve-mask ventilation as temporizing measure (especially useful in short-acting agents like GHB)
  • Circulation: IV fluid bolus for hypotension; vasopressors (norepinephrine) if refractory to fluids
  • Dextrose: Empiric D50W 50 mL IV (or D10W) if hypoglycemia suspected or cannot be immediately excluded
  • Thiamine: 100 mg IV before or with dextrose in patients at risk for Wernicke encephalopathy
  • Naloxone: 0.4–2 mg IV/IM/IN if opioid co-ingestion is suspected (miosis, opioid use history); titrate to respiratory effort, not mental status
  • Continuous monitoring: Cardiac monitor, pulse oximetry, capnography if available, frequent vital signs

GI Decontamination

  • Activated charcoal (1 g/kg, max 50 g): Consider if presentation is within ~1 hour of ingestion AND patient has intact or protected airway[1]
    • Do NOT give if altered mental status without secured airway (aspiration risk)
    • Consider for suspected barbiturate or meprobamate ingestion given potential for severe toxicity
  • Multi-dose activated charcoal (MDAC): May be beneficial for phenobarbital overdose (enhances elimination via "GI dialysis")[5]
  • Whole bowel irrigation: Consider for meprobamate (bezoar formation) or sustained-release formulations
  • Orogastric lavage is not routinely recommended

Flumazenil (Benzodiazepine Antagonist)

  • Competitive antagonist at GABA-A benzodiazepine binding site
  • Dose: 0.2 mg IV over 30 sec → 0.3 mg → then 0.5 mg doses q1min to a maximum of 3–5 mg
  • Duration of action: 45–90 min (shorter than most benzodiazepines → risk of resedation)
  • USE WITH EXTREME CAUTION / generally AVOID in the ED for undifferentiated overdose[1]
  • Contraindications / high-risk situations:
    • Chronic benzodiazepine use (may precipitate life-threatening withdrawal seizures)
    • Suspected co-ingestion of pro-convulsant agents (TCAs, bupropion, isoniazid, cocaine)
    • Known seizure disorder
    • Elevated ICP
    • Signs of significant TCA ingestion (wide QRS)
  • Reasonable uses:
    • Reversal of iatrogenic over-sedation from procedural sedation in a benzodiazepine-naive patient
    • Isolated, confirmed benzodiazepine ingestion in a benzodiazepine-naive patient (rare in practice)

Enhanced Elimination

  • Urinary alkalinization: May enhance elimination of phenobarbital (weak acid, pKa 7.2); target urine pH 7.5–8.0 with sodium bicarbonate infusion
  • Hemodialysis: Consider for severe barbiturate toxicity (particularly long-acting agents like phenobarbital) with hemodynamic instability, refractory acidosis, or rising drug levels despite supportive care[6]
    • Not effective for most benzodiazepines (highly protein-bound, large volume of distribution)

Agent-Specific Management

  • GHB: Primarily supportive; protect airway; atropine for symptomatic bradycardia; patients often awaken abruptly and may become combative; avoid intubation if possible as duration of coma is typically short (2–6 hours)[4]
  • Chloral hydrate: Avoid catecholamines (epinephrine) if dysrhythmias present — may worsen ventricular irritability; consider beta-blockers for ventricular dysrhythmias
  • Meprobamate: Monitor for prolonged toxicity from bezoar; may require whole bowel irrigation or endoscopic removal; hemodialysis effective for severe toxicity

Medication Dosing

Flumazenil 0.2mg IV over 30sec, then 0.3mg, then 0.5mg q1min (max 3-5mg total) IV

Disposition

  • Admit / ICU:
    • Respiratory depression requiring supplemental O2, NIPPV, or intubation
    • Hemodynamic instability
    • Barbiturate overdose (even if initially stable — potential for deterioration)
    • Meprobamate ingestion (risk of delayed toxicity from bezoar)
    • GHB if patient does not fully recover within expected timeframe
    • Significant co-ingestions
  • Observe in ED (minimum 4–6 hours):
    • Isolated benzodiazepine or Z-drug ingestion with mild symptoms
    • GHB intoxication — most patients recover within 2–6 hours and may be discharged if fully alert and ambulatory
  • Medical clearance for psychiatric evaluation:
    • All intentional ingestions require psychiatric assessment once medically stable
    • Ensure patient is able to participate meaningfully in psychiatric interview (not sedated)
  • Discharge:
    • Asymptomatic or fully resolved symptoms after appropriate observation
    • No evidence of co-ingestion
    • Safe disposition plan; psychiatric clearance if intentional ingestion
    • Poison control consultation recommended for all significant ingestions: 1-800-222-1222

See Also

External Links

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Simone CG, Bobrin BD. Anxiolytics and Sedative-Hypnotics Toxicity. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2023. PMID 32809628.
  2. ↑ Gummin DD, Mowry JB, Beuhler MC, et al. 2022 Annual Report of the National Poison Data System (NPDS) from America's Poison Centers: 40th Annual Report. Clin Toxicol (Phila). 2023;61(10):1-224. PMID 38084513.
  3. ↑ Kang M, Galuska MA, Ghassemzadeh S. Benzodiazepine Toxicity. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2023. PMID 29489152.
  4. ↑ 4.0 4.1 4.2 Busardò FP, Jones AW. GHB pharmacology and toxicology: acute intoxication, concentrations in blood and urine in forensic cases and treatment of the withdrawal syndrome. Curr Neuropharmacol. 2015;13(1):47-70. PMID 26074743.
  5. ↑ Chyka PA, Seger D, Krenzelok EP, Vale JA. Position paper: single-dose activated charcoal. Clin Toxicol (Phila). 2005;43(2):61-87. PMID 15822758.
  6. ↑ Mactier R, Laliberte M, Bhatt P, et al. Extracorporeal treatment for barbiturate poisoning: recommendations from the EXTRIP workgroup. Am J Kidney Dis. 2014;64(3):347-358. PMID 24953889.
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