LIMITED CAPACITY OF NEONATAL RABBITS TO ELIMINATE ENROFLOXACIN AND CIPROFLOXACIN

The pharmacokinetics of enrofloxacin (ENR) and cipro-floxacin (CIP) in newborn and young rabbits were studied, Rabbits of different ages (1- , 8-, 16-, and 30-day-old) were administered, by the intraperitoneal r oute (IP), a dose of 7.5 mg of either drug/kg, In 1-, 8-, and 16-day-o ld rabbits, broad samples were drawn by cardiac puncture, under light ether anaesthesia, at predetermined times after drug administration, I re 30-day-old rabbits, serial blood samples were drawn through an arte rial catheter. Plasma was immediately obtained and analysed using an H PLC method, ENR and CIP plasma protein binding was also determined, Th e plasma pharmacokinetic profiles of ENR and CIP obtained for 30-day-o ld rabbits agreed truth those reported in the literature for healthy a dult rabbits, Nevertheless, significant differences were observed for the body clearance, the slope of the terminal phase, the volume of dis tribution, and the area under the curve when compared with those for y ounger animals (1-, 8-, and 16-day-old rabbits), indicating a Limited capacity of neonatal rabbits to eliminate ENR and CIP, No differences were found when we compared the calculated values for ENR or CIP plasm a protein binding as a function of the postnatal age, indicating that development does not seem to alter the free fraction of these drugs in the rabbit, Taking into account that extensive placental and milli tr ansfer has been reported for these drugs after administration to pregn ant or nursing rabbits, a cautious attitude regarding their use in the se animals must be adopted.