Metabolic behaviour and tissue distribution of nalidixic acid in chickens.

The metabolic behaviour and tissue distribution of nalidixic acid in normal and E. coli infected chickens were carried out using spectrofluorimetric and microbiological techniques following a single and multiple oral administration of 25 mg/kg b. wt. The obtained results revealed that free nalidixic acid (free NA) is the major fraction of the total drug concentration in serum, liver and kidneys. The free active nalidixic acid was in a higher concentration than hydroxynalidixic acid (free HNA) and both conjugates of NA and HNA following single and multiple oral administration. The obtained results showed that nalidixic acid was highly distributed in all tissues in normal and E. coli infected chickens, with the highest concentrations in kidneys, liver and heart and lowest concentrations in brain, muscles and intestine following oral administration of 25 mg/kg b. wt. twice daily for 5 successive days. Spectrofluorimetic technique was more sensitive for nalidixic acid determination than microbiological method. Nalidixic acid revealed longer withdrawal time in diseased chickens than in normal chickens.