Toxic alcohols: documentation that holds up
Methanol and ethylene glycol are poisons whose parent compound is nearly harmless — it's the metabolite that blinds and destroys kidneys. The defensible chart records the osmolar and anion gaps with the time since ingestion, and shows treatment wasn't delayed waiting for a level.
01What's at stake
A patient can look merely drunk for hours while alcohol dehydrogenase converts the alcohol into formic acid (methanol → blindness) or glycolic/oxalic acid (ethylene glycol → renal failure, hypocalcemia). Early on, the osmolar gap is high and the anion gap normal; later that reverses. The central failure is using one normal gap, or a pending level, to exclude a lethal ingestion.
02The agents & their harm
- Methanol (windshield washer, wood alcohol) → formate → visual loss/blindness, anion-gap acidosis, basal ganglia injury.
- Ethylene glycol (antifreeze) → glycolic/oxalic acid → renal failure, calcium oxalate crystals, hypocalcemia, dysrhythmias.
- Isopropanol (rubbing alcohol) → acetone → ketosis without acidosis; supportive care only (do not give fomepizole).
- Propylene glycol (IV med diluent — lorazepam, phenobarbital) → lactic acidosis, usually iatrogenic.
03Diagnosis — two gaps, read against time
- Anion gap = (Na + K) − (Cl + HCO₃); rises as the alcohol is metabolized to acid.
- Osmolar gap = measured − calculated osmolality [2·Na + BUN/2.8 + glucose/18 + ethanol/4.6]. Include the ethanol level.
- The reciprocal relationship: early = high osmolar gap, normal anion gap; late = normal osmolar gap, high anion gap. A normal gap does not exclude ingestion. → timing matters
- Don't rely on urine fluorescence (unreliable) or calcium oxalate crystals (can mislead); beware a falsely elevated lactate from glycolate.
- In any suicidal ingestion, send acetaminophen and salicylate levels.
Skip the typing
Work the case in the Overdose / Ingestion Workup — it records co-ingestant levels, the ECG, poison-control contact, and the observation period, and assembles an MDM you can adapt to document the gaps, the empiric-treatment reasoning, and toxicology/nephrology involvement.
04Management — treat before the level returns
- Fomepizole (block ADH) for level >20 mg/dL or suspicious history with pH <7.3, HCO₃ <20, osmolar gap >10, or high suspicion — start while labs are pending. Adjust to every 4 hours during dialysis.
- Sodium bicarbonate for acidosis (limits formate diffusion into the CNS).
- Cofactors: folate/folinic acid for methanol; thiamine + pyridoxine (± magnesium) for ethylene glycol.
- Hemodialysis once a severe anion-gap acidosis or end-organ damage is present — fomepizole alone won't reverse established toxicity; involve nephrology.
- Contact poison control / toxicology — and don't give fomepizole for isolated isopropanol.
05What to document
06Where charts fail
- Excluding ingestion on a single normal osmolar or anion gap.
- Waiting for a level before starting fomepizole when the history is suspicious.
- Giving fomepizole for isolated isopropanol (prolongs intoxication).
- Forgetting acetaminophen/salicylate levels in a self-harm ingestion.
- Not arranging dialysis (or nephrology) once a severe acidosis/end-organ damage exists.
07Sources
- Beauchamp GA, Valento M. Toxic alcohol ingestion: prompt recognition and management in the emergency department. Emergency Medicine Practice (EB Medicine). 2016;18(9).
- Barceloux DG, Krenzelok EP, Olson K, et al. AACT practice guidelines on the treatment of ethylene glycol poisoning. J Toxicol Clin Toxicol. 1999;37(5):537-560.
- Brent J. Fomepizole for the treatment of pediatric ethylene and diethylene glycol, butoxyethanol, and methanol poisonings. Clin Toxicol. 2010;48(5):401-406.
- Jacobsen D, Bredesen JE, Eide I, et al. Anion and osmolal gaps in the diagnosis of methanol and ethylene glycol poisoning. Acta Med Scand. 1982;212(1-2):17-20.
© 2026 Kim Trinh, MD. All rights reserved. Educational only — synthesized from EB Medicine and primary literature. Synthetic examples. Not medical advice — apply local protocol and judgment.