Ethanol
Ethanol (ethyl alcohol) is primarily used in veterinary medicine as an **antidote** for **ethylene glycol (antifreeze)** or **methanol** toxicity. - **Fomepizole (4-MP)** is generally the modern treatment of choice for ethylene glycol poisoning, but ethanol remains a readily available and economical alternative if the patient presents within a few hours of ingestion. - **Alternative uses**: Percutaneous injection of 95% ethanol has been used successfully to treat feline hyperthyroidism. Aerosolized ethanol has been used as a mucokinetic agent in horses. > **Clinical Pearl**: In emergency settings where pharmaceutical-grade ethanol is unavailable, commercial spirits (like vodka or grain alcohol/Everclear) are frequently compounded into IV fluids to create life-saving infusions.
Mechanism: Ethanol acts by **competitively inhibiting the enzyme alcohol dehydrogenase**. - Ethylene glycol/Methanol + **Alcohol dehydrogenase** โ Toxic metabolites (glycoaldehyde, glycolate, glyoxalate, and oxalic acid). - By occupying the enzyme, ethanol prevents this conversion, allowing the parent toxin (ethylene glycol or methanol) to be excreted primarily unchanged in the urine. - **Note**: For alcohol to be effective, it must be given very early after ingestion; it is seldom useful if started 8 hours after a significant ingestion.
Dosing by species
- Ethylene glycol poisoning ยท 5.5 mL/kg IV q4h for 5 treatments, then q6h for four additional treatments ยท IV ยท q4h then q6h ยท 9 treatments total ยท As a 20% solution; dosed as a CRI over 1 hour
- Ethylene glycol poisoning ยท 8.6 mL/kg slowly IV followed by a CRI of 1.43 mL/kg/hr ยท IV ยท CRI ยท at least 36 hours although 48 hours is probably better ยท Make a 7% ethanol solution. If EG test was positive initially, check before stopping treatment; discontinue if it reverts to negative.
- Ethylene glycol toxicity ยท 5.5 ml of 20% ethanol solution/kg ยท IV ยท q4h for 5 treatments, then q6h for 4 additional treatments ยท 9 treatments total ยท Adjust dose to maintain blood ethanol levels above 35 mg/dl.
- Ethylene glycol toxicity (CRI method) ยท Loading dose of 1.3 ml/kg of 30% solution, then 0.42 mg/kg/h ยท IV ยท CRI ยท 48 hours ยท Constant rate infusion method.
- Ethylene glycol toxicity (mild cases) ยท As directed (equivalent to IV dosing) ยท PO ยท As directed ยท Until toxicity resolves ยท For clinically mild cases with minimal CNS signs; vodka is often used.
- Ethylene glycol poisoning ยท 5 mL/kg IV q6h for 5 treatments, then q8h for four additional treatments ยท IV ยท q6h then q8h ยท 9 treatments total ยท As a 20% solution; dosed as a CRI over 1 hour
- Ethylene glycol poisoning ยท 8.6 mL/kg slowly IV followed by a CRI of 1.43 mL/kg/hr ยท IV ยท CRI ยท at least 36 hours although 48 hours is probably better ยท Make a 7% ethanol solution. If EG test was positive initially, check before stopping treatment; discontinue if it reverts to negative.
Routes of administration
Contraindications
- Concurrent use with fomepizole (usually contraindicated)
Adverse effects
- CNS depression
- Respiratory depression
- Diuresis
- Hypocalcemia
- Metabolic acidosis
- Pulmonary edema
- Injection site pain and infection
- Phlebitis
- Extravasation injury
- Bronchoconstriction and irritation (when aerosolized)
Drug interactions
- Bromocriptine ยท Alcohol may increase the severity of side effects seen with bromocriptine
- Activated Charcoal ยท Will inhibit absorption of orally administered ethanol; do not use if administering ethanol orally
- CNS Depressant Drugs (barbiturates, benzodiazepines, phenothiazines) ยท Alcohol may cause additive CNS depression
- Fomepizole (4-MP) ยท Inhibits alcohol dehydrogenase; ethanol metabolism is reduced significantly and alcohol poisoning (CNS depression, coma, death) can occur. Use together is generally not recommended.
- Insulin and antidiabetic drugs ยท Alcohol may affect glucose metabolism and the actions of insulin or oral antidiabetic agents
- Chlorpropamide, furazolidone, metronidazole ยท A disulfiram reaction (increased acetaldehyde with tachycardia, vomiting, weakness) may occur
- Fomepizole ยท Increases risk of severe alcohol toxicity; concurrent use should be avoided. ยท major
Monitoring
- Alcohol blood levels (maintain at 100 to 130 mg/dL; safer to maintain >130 mg/dL than to fall below 100 mg/dL)
- Ethylene glycol or methanol levels
- Degree of CNS effect
- Fluid and electrolyte status
Overdose
If clinical signs of overdosage occur (**lateral nystagmus, respiratory depression, profound obtundation**), either slow the infusion or discontinue temporarily. Alcohol blood levels may be used to monitor both efficacy and toxicity of alcohol.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.