Pharmacology of Ethylene Glycol

ETHYLENE GLYCOL

Polyhydric alcohols such as ethylene glycol (CH₂OHCH₂OH) are used as heat exchangers, in antifreeze formulations, and as indus-trial solvents. Young children and animals are sometimes attracted by the sweet taste of ethylene glycol and, rarely, it is ingested intentionally as an ethanol substitute or in attempted suicide. Although ethylene glycol itself is relatively harmless and elimi-nated by the kidney, it is metabolized to toxic aldehydes and oxalate.

Three stages of ethylene glycol overdose occur. Within the first few hours after ingestion, there is transient excitation fol-lowed by CNS depression. After a delay of 4–12 hours, severe metabolic acidosis develops from accumulation of acid metabo-lites and lactate. Finally, delayed renal insufficiency follows depo-sition of oxalate in renal tubules. The key to the diagnosis of ethylene glycol poisoning is recognition of anion gap acidosis, osmolar gap, and oxalate crystals in the urine in a patient without visual symptoms.

As with methanol poisoning, early fomepizole is the standard treatment for ethylene glycol poisoning. Intravenous treatment with fomepizole is initiated immediately, as described above for methanol poisoning, and continued until the patient’s serum ethylene glycol concentration drops below a toxic threshold (20–30 mg/dL). Intravenous ethanol is an alternative to fomepi-zole in ethylene glycol poisoning. Hemodialysis effectively removes ethylene glycol and its toxic metabolites and is recommended for patients with a serum ethylene glycol concentration above 50 mg/dL, significant metabolic acidosis, and significant renal impairment. Fomepizole has reduced the need for hemodialysis, especially in patients with less severe acidosis and intact renal function.