Increased urinary riboflavin excretion resulting from boric acid ingestion.

The urinary excretion of riboflavin (vitamin B2) was determined in 14 patients, both children and adults, after the ingestion of boric acid. These patients reported to the New York City Poison Control Center during a 2 1/2 year period. Riboflavin was determined by a modification of a previously described method which is based upon competitive protein binding. Boric acid ingestion was associated with greatly increased urinary riboflavin excretion in approximately two thirds of the patients. Most of the riboflavin appeared to be excreted within the first 24 hr after ingestion of boric acid. These data provide evidence of a previously unrecognized hazard of boric acid ingestion in patients.