Toxicological

Rapid Review

• Mechanism of Action: Adsorbent agent. Large surface area of charcoal binds to toxins and prevents systemic absorption.
• Indications: Toxic ingestions/drug overdoses (solids only); should be administered within 1-2 hours of ingestion.
• Contraindications: Risk of aspiration, ingestion of caustic material
• Dosage: 25-100mg PO
• Onset: Begins within 1 minute; achieves equilibrium within 10-25 minutes.
• Duration: Up to 4 hours
• Adverse Reactions: aspiration, bowel obstruction.
• Special Considerations: N/A

Pearls

Deep Dive

• Back to Black: A Review of Activated Charcoal (EM Ottawa)

Rapid Review

• Mechanism of Action: Anticholinergic and parasympatholytic; antagonizes acetylcholine receptors and prevents activation of parasympathetic nervous system.
• Indications: organophosphate toxicity; bradycardia. May also be used to reverse effects of paralytics. 
• Contraindications: allergy; primary glaucoma
• Dosage: symptomatic bradycardia: 0.5 mg rapid IV push; organophosphate toxicity: 1-3 mg IV/IM/SC. Paralytic reversal: 1.2 mg IV push
• Onset: 2-4 minutes
• Duration: 5 hours
• Adverse Reactions: dry mouth, blurred vision, tachycardia, hyperthermia

Pearls

Deep Dive

• Atropine Not Needed For RSI (emDocs)

Rapid Review

• Mechanism of Action: Benzodiazepine antagonist; competitively inhibits GABA/benzodiazepine receptor sites
• Indications: Benzodiazepine overdose
• Contraindications: Hypersensitivity, use of benzodiazepine to control seizures
• Dosage: 0.2 mg slow IV push initially. Repeat every 60 seconds prn. Max dose 1 mg.
• Onset: 1-2 minutes
• Duration: 19-50 minutes
• Adverse Reactions: Sedation, seizure, arrhythmias, confusion, nausea/vomiting

Pearls

Deep Dive

• What’s the Deal With Flumazenil? (emDocs)

Rapid Review

• Mechanism of Action: Antidote; inhibits alcohol dehydrogenase
• Indications: Methanol or ethylene glycol toxicity
• Contraindications: Allergy
• Dosage: 15 mg/kg IV loading dose, then 10 mg/kg q12 hours 
• Onset: 1.5 – 2 hours
• Duration: Half life not determined
• Adverse Reactions: Headache, nausea, bradycardia, hypotension

Pearls

Deep Dive

• Fomepizole (Drugs.com)

Rapid Review

• Mechanism of Action: Lipid emulsion; unknown mechanism, but thought to create a “lipid sink” in the blood where lipophilic anesthetic agents can dissolve, thus reducing systemic circulation. Available in 10%, 20%, and 30%.
• Indications: Local anesthetic systemic toxicity (LAST)
• Contraindications: Severe egg allergy, 
• Dosage:
  • Weight > 70kg: 100mL bolus (20%), followed by 200-250mL infusion over 20-30 minutes
  • Weight <70kg: 1.5mL/kg bolus (20%), followed by 0.25 mL/kg/minute infusion
• Half-Life: 15 minutes
• Adverse Reactions: Fat embolism, hypersensitivity reactions, pancreatitis, hypertriglyceridemia

Pearls

Deep Dive

• Lipid Emulsion Therapy (PubMed)

Rapid Review

• Mechanism of Action: Oxime antidote. Reactivates the acetylcholinesterase enzyme to promote clearance of acetylcholine at muscarinic and nicotinic sites.
• Indications: Organophosphate toxicity
• Contraindications: Allergy to drug/class
• Dosage: 1-2 grams IV over 5-10 minutes or 600 mg IM X 3 doses (15 minutes apart)
• Onset: 5-15 minutes
• Duration: 3-4 hours
• Adverse Reactions: Blurred vision, diplopia, dizziness, tachycardia, hypertension

Pearls

Deep Dive

• Pralidoxime (PubMed)

Rapid Review

• Mechanism of Action: Antidote/Mucolytic; helps replete glutathione reserves in the liver, which helps protect the liver from hepatotoxic NAPQI metabolite. Also functions as a mucolytic to help break down thick pulmonary secretions.
• Indications: Acetaminophen toxicity
• Contraindications: Allergy to drug/class
• Dosage: Three separate infusions:
  • First dose: 150mg/kg in 100 mL D5W over 60 minutes
  • Second dose: 50mg/kg in 250 mL D5W over 4 hours
  • Third dose: 100 mg/kg in 500 mL D5W over 16 hours
• Onset: Generally rapid onset
• Duration: Generally short duration
• Adverse Reactions: Nausea/vomiting, anaphylaxis 
• Special Considerations: Almost 100% effective if given within 8 hours of ingestion for maximum benefit. May still be beneficial after >24 hours.

Pearls

Deep Dive

• N-acetylcysteine (Life in the Fast Lane)

Rapid Review

• Mechanism of Action: Opiate antagonist; competitively binds to mu, kappa, and sigma opiate receptor sites in the CNS for reversal of opiate toxicity and improvement of respiratory drive.
• Indications: Opioid toxicity (recreational or iatrogenic)
• Contraindications: Allergy to class/drug
• Dosage: 0.4 – 2.0 mg (IV/IM/SC), repeat q 2-3 minutes prn. Max dose 10 mg
• Onset: 1-2 minutes
• Duration: 20-90 minutes
• Adverse Reactions: Non-cardiogenic pulmonary edema, opioid withdrawal (diaphoresis, tachycardia, agitation)
• Special Considerations: Patients with opiate overdose should be held in the ED until naloxone wears off (usually 1-3 hours). Consider discharging patients with naloxone in-hand. 

Pearls

Deep Dive

• Narcan or Nar-can’t: Tips and Tricks to Safely Reversing Opioid Toxicity (EM:RAP)

Rapid Review

• Mechanism of Action: Vitamin; combines with ATP in liver, kidneys, and leukocytes to produce thiamine diphosphate, which acts as a coenzyme in carbohydrate metabolism. Used to prevent brain damage (encephalopathy) from thiamine-depleted states.
• Indications: Alcoholism, beriberi anorexia, bulimia, pregnancy, malignancies
• Contraindications: Allergic reactions to vitamin supplements
• Dosage:
  • Beriberi: 5-30 mg TID x 1 month
  • Wernicke’s Encephalopathy: 500mg IV TID x 2 days
• Onset: Rapid
• Duration: Depends on degree of deficency
• Adverse Reactions: Anaphylaxis, pruritus, injection site pain
• Special Considerations: None

Pearls

Deep Dive

• Myths of Toxicology: Thiamine Before Dextrose (Emergency Medicine News)