STUDIES OF THE ANTIBACTERIAL ACTIVITY AND PHARMACOKINETICS OF ENROFLOXACIN (BAYTRIL) IN LACTATING COWS

The minimum inhibition (MIC) of Enrofloxacin (Baytril) was determined in a dilution series test for a total of 715 bacterial pathogens out o f mastitis milk. Baytril was highly active against E. Coli and Staph. aureus (E. coli, 200 strains: MIC range 0,03 - 1,0, median value 0,06, MIC 90% 0,14 mug/ml; Staph. aureus; 206 strains: MIC range 0,03-0,5, median value 0,12, MIC 90% 0,31 mu/ml). The antibacterial effect again st streptococci (309 strains) was not sufficient (MIC range 0,25 - 8,0 , median value 1,0, MIC 90% 2,0 mug/ml). The concentration of active s ubstance of Baytril in blood serum and milk after a single dose of 2,5 mg/kg body weight administered intravenously, intramuscularly or subc utaneously, were determined microbiologically by means of an agar diff usion test. Concentrations im milk were much higher and persisted long er in milk as compared to blood serum. This means, Baytril penetrated the blood-milk-barrier easily and accumulated and persisted in the mil k. Because of the high concentration and long persistance of Baytril i n milk after parenteral administration this course of treatment will b e of therapeutical relevance in acute mastitis.