FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam

What is the role of fomepizole in the treatment of ethylene glycol overdose?

1. It enhances the metabolism of ethanol

2. It decreases the breakdown of ethylene glycol into toxic metabolites

3. It induces vomiting in patients

4. It promotes hemodialysis effectiveness

The correct answer is: It decreases the breakdown of ethylene glycol into toxic metabolites

Fomepizole is primarily used as an antidote in cases of ethylene glycol overdose due to its action as a competitive inhibitor of the enzyme alcohol dehydrogenase. By inhibiting this enzyme, fomepizole effectively decreases the breakdown of ethylene glycol into its toxic metabolites, which include glycolic acid and oxalic acid. These metabolites are responsible for the majority of the toxicity associated with ethylene glycol ingestion, leading to metabolic acidosis and renal damage. When fomepizole is administered, it prevents the conversion of ethylene glycol into these harmful substances, thereby mitigating the toxic effects and allowing for the body's normal clearance processes to function without being overwhelmed by the accumulation of toxic metabolites. This is critical in the treatment of ethanolic and methanol poisoning, highlighting its significance in managing ethylene glycol overdoses as well. The other options do not accurately describe the function of fomepizole. It does not enhance ethanol metabolism, induce vomiting, or directly promote the effectiveness of hemodialysis. Therefore, its primary role remains focused on interfering with the metabolic pathway that leads to the formation of toxic byproducts from ethylene glycol.