Ethyl alcohol intoxication usually follows the ingestion of fermented foodstuffs, alcoholic beverages or other products containing ethylene glycol. Puppies have been poisoned following contact with dishwashing detergent containing ethanol.
Methanol intoxication has been reported in dogs after ingesting antifreeze (98% methanol and 2% dyes) (nb. most antifreeze in NZ is ethylene glycol). Although methanol abuse in humans has been reported for years, it is seldom reported in veterinary literature.
With ethanol, death usually occurs as a result of respiratory failure.
Methanol is rapidly absorbed from the gastrointestinal and respiratory tracts. It is eliminated unchanged from the lungs, but is oxidised in the liver by alcohol dehydrogenase to formic acid and formaldehyde. These metabolites are then eliminated in the urine. Similar to the ethylene glycol, it is the metabolites which produce a metabolic acidosis resulting in most of the toxic signs, including irreversible retinal damage and blindness. Methanol metabolism occurs at a rate that is independent of its concentration. As the metabolites are the toxic principles, therapy is aimed at preventing their formation by blocking the appropriate enzyme system.
The clinical signs are very similar to inebriation following ethylene glycol poisoning. Central nervous system depression and ataxia are prominent signs. In man, methanol intoxication has been associated with vomiting, abdominal pain, dyspnoea, hypothermia, coma and death.
A delay in onset of abdominal pain (3 to 24 hours after ingestion) is frequently observed; metabolic acidosis develops 2 to 12 hours after ingestion. When exposure is by inhalation, lung haemorrhage, oedema, congestion and pneumonia may be seen. Fatty infiltration and degeneration of the liver, cardiac dilation and degeneration and occasionally degenerative changes in the CNS also occur.
Differentiating between ethylene glycol and ethanol is important, as ethanol is commonly used as an antidote for ethylene glycol. The history, breath odour (sweet smelling), plasma osmolarity and blood concentrations of the toxicant can determine the diagnosis.
The treatment of ethanol toxicosis is largely supportive. Induce emesis if the animal is fully conscious, and provide fluids, bicarbonate, and ventilation if required.
Methanol toxicosis treatment consists of inducing vomiting or gastric lavage in a conscious patient and giving ethanol to prevent the formation of toxic metabolites (5.5 ml of 20% ethanol/kg bodyweight iv, diluted in 0.9% saline and given over 6 hours). Care must be taken as there is the possibility of potentiating the methanol induced CNS depression by ethanol therapy. Maintain body temperature, correct acidosis and initiate peritoneal dialysis.
Daniel, J.D. and Spyker, D.A. (1979). The acute toxicity of ethanol. Vet Hum Toxicol. 21:272-276
Del Mar, E. (1984). Apparent ethanol poisoning in puppies shampooed in dishwashing detergent. Vet Med/Sm Ani Clin. 79:318-319.
Freemyer, F.G., Hamar, D.W. and Jones, R.L. (1984). Ethanol toxicosis secondary to sourdough ingestion in a dog. J AmVet Med Assoc. 184:1513-1514.
Hurd-Kuenzi, L.A. (1983). Methanol intoxication in a dog. J AmVet Med Assoc. 183:882-883.
Tarr, B.D., Winters, L.J., Moore, M.P., Cowell, R.L. and Hayton, W.L. (1985). Low dose ethanol in the treatment of ethylene glycol poisoning. J Vet Pharmacol Therap. 8:254-262.
