The human biotransformation of nalidixic acid.

Authors have developed new chemical methods for studying the human metabolism of nalidixic acid. The methods are suited for the quantitative determination of nalidixic acid, hydroxynalidixic acid, nalidixic acid glucuronide, hydroxynalidixic acid-glucuronide, and of free and total glucuronic acid excretion. The total urinary excretion of NA and its metabolites was found to be 50 to 100% of the ingested dose. The percentual distribution of the individual metabolites was as follows: NA 0,5-5, HNA2,5-6, NAG24-80, and HNAG11-26%. It was unanimously proved by enzymatic decomposition and specific chemical reactions that the excreted conjugates were monoglucuronides. The significance of individual differences, bilirubin metabolism, urinary pH and the pharmacokinetical behaviour of the individual metabolites is discussed from the therapeutic view.