ENROFLOXACIN THEOPHYLLINE INTERACTION - INFLUENCE OF ENROFLOXACIN ON THEOPHYLLINE STEADY-STATE PHARMACOKINETICS IN THE BEAGLE DOG

Enrofloxacin, a quinolone antibiotic developed exclusively for use in animals, was investigated for its effects on the steady-state pharmaco kinetics of theophylline in six healthy Beagle dogs. A sustained-relea se theophylline formulation was given alone (20 mg/kg per os twice dai ly at 12 h intervals) for 9 days and then co-administered with enroflo xacin (5 mg/kg i.v, once a day) for 5 days. Mean trough theophylline c oncentrations progressively and significantly increased during the fiv e days of enrofloxacin co-administration. Theophylline clearance and c oncentration-time profile were significantly changed by enrofloxacin c o-administration. No significant change was observed in enrofloxacin p harmacokinetics, The kinetic interaction between theophylline and enro floxacin could be of clinical significance and may require plasma drug concentration monitoring and adjustment of theophylline dosage.