FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam 2026 - Free NABP Practice Questions and Study Guide

The first sign of ethylene glycol poisoning is metabolic acidosis. Ethylene glycol is a toxic substance commonly found in antifreeze, and its ingestion leads to a series of biochemical changes in the body. One of the primary metabolites of ethylene glycol is glycolic acid, which, when produced in significant amounts, contributes to a metabolic acidosis. This condition arises because the accumulation of acid in the bloodstream results in a decrease in blood pH.

Metabolic acidosis is often noted before other more severe symptoms manifest, making it a crucial early indicator of ethylene glycol toxicity. While visual disturbances, gastrointestinal bleeding, and neurological symptoms can occur as the poisoning progresses, they are typically not the initial signs.

For instance, visual disturbances may arise later in the course due to the formation of calcium oxalate crystals in the eyes, while neurological symptoms could develop from various factors, including central nervous system involvement or hypoxia due to acidosis. Gastrointestinal bleeding is uncommon and is more likely associated with other toxic ingestions or complications. Hence, identifying metabolic acidosis early is essential in managing ethylene glycol poisoning effectively.