Final answer:
Ethanol therapy is the most effective treatment for ethylene glycol poisoning when 4-methylpyrazole is not available. It competes with ethylene glycol for the same liver enzyme and slows down the production of toxic metabolites.
Step-by-step explanation:
The most effective treatment for ethylene glycol poisoning, if 4-methylpyrazole is not available, is ethanol therapy. Ethanol competes with ethylene glycol for the same liver enzyme, alcohol dehydrogenase, and slows down the conversion of ethylene glycol into toxic metabolites. Ethanol is administered orally or intravenously and its dosage is adjusted to maintain a blood ethanol concentration between 100-150 mg/dL. During administration, blood ethanol levels should be monitored to ensure therapeutic levels are maintained.