What is the percentage of acetaminophen excreted unchanged in urine?

The percentage of acetaminophen that is excreted unchanged in urine is approximately 5%. This relatively low percentage reflects the metabolic pathways of acetaminophen in the body. When acetaminophen is ingested, it undergoes extensive hepatic metabolism, where it is primarily conjugated with sulfate and glucuronide, transforming it into various metabolites that are water-soluble and can be eliminated through urine.

The small fraction that is excreted unchanged indicates that the vast majority of the drug is processed and modified by the liver before excretion. Therefore, selecting 5% aligns with established pharmacological knowledge regarding the metabolism and elimination of acetaminophen from the body.