Isopropyl alcohol toxicity

Background

• Main component of rubbing alcohol
• Hallmark is osmolar gap, ketosis, that is without acidosis
  • Metabolized to acetone, not to an acid
• Takes 30-60 min for acetone to appear in blood; 3 hr to appear in urine
• Lethal Dose: 4-8 g/kg or 250 mL in average adult (calculated using volume of pure isopropyl alcohol)
  • Typical store bought rubbing alcohol is 70% isopropyl alcohol by volume, so lethal dose is ~ 350 mL

Pharmacology

• Unlike other toxic alcohols (methanol, ethylene glycol), toxic effects caused by parent agent (IA) rather than metabolite (acetone)
• Metabolized to acetone by alcohol dehydrogenase
• Maximal distribution in ≤ 2 hours
• Lethal dose > 200 mg/dL, although variable literature

Clinical Features

• CNS depression
  • Similar to ETOH intoxication, but longer-lasting
  • Usually peaks in first hour of ingestion
• GI
  • Nausea/vomiting / abdominal pain / hemorrhagic gastritis
• Respiratory depression
  • Fruity breath from acetone
• Hypotension, hypothermia from peripheral vasodilation
• Hypoglycemia (in malnourished patients)

Differential Diagnosis

• Starvation ketoacidosis
• Diabetic Ketoacidosis
• Inborn errors of metabolism
• Salicylate Toxicity
• Acetone ingestion

Sedative/hypnotic toxicity

• Absinthe
• Barbiturates
• Benzodiazepines
  • Flunitrazepam (Rohypnol)
• Chloral hydrate
• Gamma hydroxybutyrate (GHB)
• Baclofen toxicity
• Opioids
  • Lomotil toxicity
  • Loperamide toxicity
• Toxic alcohols
  • Ethanol
  • Ethylene glycol
  • Isopropyl alcohol
  • Methanol
• Xylazine toxicity

Evaluation

Work-Up

• Fingerstick glucose
• Complete metabolic panel
• Serum ketones
• Serum Osmolality
• Urinalysis
• VBG
• Aspirin/Tylenol levels
• ECG
• Serum isopropyl alcohol level (if available)
• Total CK

Evaluation

• Osmolal gap > 10; see Osmolal or Osmolar Gap
• Absence of anion gap
• Absence of metabolic acidosis
• Absence of serum beta hydroxybutyrate
• Presence of serum and urine ketones
  • Consider other diagnosis if absent 2hr after ingestion
• Creatinine may be falsely elevated due to acetone interference with laboratory measurement of Cr

Toxic Alcohols Anion/Osmolar Gaps

Osmolar gap	Metabolic acidosis	Osmolar gap	Anion gap	Ketones	Ca Oxolate stones	Reduced vision	Management
Ethanol	+	+	+ (if ketoacidosis)	+	-		Mainly supportive
Ethylene glycol	+	+	+	-	+	-	Fomepizole, Thiamine, Pyridoxine, +/- Dialysis
Methanol	+	+ (early on, then disappears)	+	-	-	+	Fomepizole or ethanol, Folinic acid, +/- Dialysis
Isopropyl alcohol	-	+	-	+	-	+	Mainly supportive
Propylene gylcol	+	+ (initially)	+ (converted to lactate)	-	-	-

Management

• Treatment is supportive.
• No role for fomepizole or ethanol
  • Blockade of alcohol dehydrogenase (ADH) will prolong intoxication
• Hemodialysis indications:
  • Hypotension
  • Comatose
  • Consider if IA serum level >200mg/dL

Disposition

• Generally may be discharged once clinically sober.

See Also

• Toxic alcohols
• In-Training Exam Review