Ethanol (antidote)

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Related FACEM curriculum (2022) learning objectives:

• ME 3.8.1.6(e) Principles of management of toxicological presentations including: Indications for antidotes
• ME 3.8.2.4 Identify the appropriate antidote or antivenom.

Presentations

• Pharmaceutical-grade ethanol: 20 mL ampoules (pure ethanol).
• Commercial alcoholic beverages: alcohol content 5%–70%.

Toxicological Indications

• Methanol poisoning (confirmed or suspected).
• Ethylene glycol poisoning (confirmed or suspected).

Contraindications

• Recent ingestion of disulfiram or drugs causing disulfiram-like reactions.

Mechanism of Action

• Alcohol dehydrogenase (ADH) has a 20× higher affinity for ethanol than methanol or ethylene glycol.
• Ethanol competitively inhibits toxic alcohol metabolism by blocking ADH receptor sites.
• Effective inhibition at ethanol concentrations >100 mg/dL (22 mmol/L).

Pharmacokinetics

• Rapid oral absorption; widely distributed in total body water.
• Crosses placenta and blood-brain barrier.
• Liver metabolism via ADH and aldehyde dehydrogenase; saturable metabolic capacity with variability between individuals.

Administration

General

• Begin therapy in a monitored setting; check mental status and ethanol levels every 2 hours.
• Routes: oral, nasogastric, or intravenous (IV).
• Maintain blood ethanol concentration: 100–150 mg/dL (22–33 mmol/L).

Dosing

Oral/Nasogastric Administration

• Loading dose: 1.8 mL/kg of 43% ethanol (e.g., 3 × 40 mL vodka shots for 70-kg adult).
• Maintenance: 0.2–0.4 mL/kg/hour of 43% ethanol (40 mL/hour).

Intravenous Administration

• Loading dose: 8 mL/kg of 10% ethanol.
• Maintenance: 1–2 mL/kg/hour of 10% ethanol.
• Prepare 10% ethanol by adding 100 mL of pure ethanol to 900 mL of 5% dextrose.
• Adjust doses to maintain desired ethanol concentrations.
• Continue until definitive toxic alcohol treatment (e.g., haemodialysis).

Adverse Drug Reactions

• Local phlebitis: Common with IV solutions.
• Ethanol intoxication: Reduce infusion rate if ethanol levels >150 mg/dL (33 mmol/L).
• Hypoglycaemia: Monitor carefully in children.

Specific Considerations

• Pregnancy: Crosses the placenta; no contraindication in pregnant patients with toxic alcohol poisoning.
• Paediatric: Monitor closely for hypoglycaemia; no contraindication in toxic alcohol poisoning.

Handy Tips

• IV ethanol can be challenging to source; alcoholic spirits are readily available for oral use.
• Skip the loading dose in already ethanol-intoxicated patients.
• Breath ethanol testing may replace repeated blood ethanol measurements during maintenance.

Pitfalls

• Delayed therapy initiation.
• Failure to maintain therapeutic ethanol concentrations due to inadequate monitoring.

Controversies

• Superiority of fomepizole over ethanol for ADH inhibition.
• Efficacy of ethanol for less common toxic alcohols (e.g., glycol ethers, diethylene glycol, propylene glycol).
• Need for continued ethanol maintenance after starting haemodialysis.