Tissue distribution of oxacillin and ampicillin in the isolated perfused bovine udder

In vivo, tissue distribution of intramammarily administered antibiotics is mostly only assessed by sampling milk and blood. Therefore, the described s tudy analysed whether measurement of tissue concentrations makes sense in v itro instead. Isolated bovine udders were perfused with gassed and warmed T yrode solution. To four front and rear quarters each, 1000 mg oxacillin in 7.5 ml vehicle was administered intracisternally, completely formulated as sodium monohydrate in two lactation ointments (with or without sodium dodec ylsulphate) or 80 % as benzathine salt in a dry-off ointment. Over 3 h, per fusate and glandular tissue from different locations were sampled and analy sed by high pressure liquid chromatography. With increasing vertical distan ce to the teat base, the tissue concentration of antibiotics decreased. Wit h the lactation ointment containing sodium dodecylsulphate, lower oxacillin concentrations were reached in glandular tissue and lymph nodes compared t o those without. The ointments led to a higher recovery of oxacillin in gla ndular tissue than in perfusate. Aluminium monostearate in the dry-off oint ment caused an even poorer absorption of oxacillin into perfusate. The isol ated perfused bovine udder is suitable to study the tissue distribution of antibiotics, since the results were mainly comparable with the few existing in vivo studies and show the influence of different formulations.