Enrofloxacin (Bayad@) was injected into arteries supplying the udder of dairy cows. The idea was to avoid primary dismbution, metabolism and elimination and thus to deliver the drug to the target organ at hgha concentration. Enrofloxacin injected into the abdominal aorta or the external iliac artery resulted in high initial enrofloxacin retention by the udder and high milk concentrations.Injection of enrofloxacin into the abdominal aorta resulted in 2.2 times higher milk peak concentration of the drug than intravenous injection into the jugular vein. Injection of the drug into one of the two external iliac arteries dowed dmg concentrations of milk from the udder halves to be compared: when enrofloxacin w a s injected into the right external iliac artery, the peak milk enrofloxacin concentration from the right udder half was 4.8 times that of the left udder half. The bulk of enrofloxacin was absorbed from the milk compartment of the udder before the next regular milking 6.5 h later. By this time, the metabolite cipmfloxacin had accumulated in milk. Pharmacokinetic values for enrofloxacin and its metabolite ciprofloxacin are given separately for serum and milk whey following thrcc intravascular dosing mutes SANDHOLM, 1995). Drug concentrations in milk are low for many oral and parented antibacterial preparations. The drug can be targeted into a selected organ by injecting the dose into the artery supplying blood to that organ. Intra-arterial injections into cows have been a common practice in the former east block countries: Estonia, East Germany and Russia. The intra-arterial route of administration is rarely used in Western type veterinary practice. Although there have been a few reports on the clinical efficacy of antibacterials administered by the intra-arterial route in mastitis and metritis (LIPOV~SEV, 1964; COLOMBO land GUALLINI, 1967; MA= et al., 1987, sound pharmacokinetic studies are laclung. The us. CoplmBht acents S~D~~C 0931-184X/96/4306-0377$11.50/0

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