Some pharmacokinetical aspects of ampicillin trihydrate and its therapeutic efficacy in experimental Escherichia coli infection in poultry.

Pharmacokinetical studies of ampicillin trihydrate indicate rapid absorption and very fast elimination in poultry. No significant differences in pharmacokinetical properties of this drug were demonstrated either between different hybrids of various ages or between E. coli-infected and normal broilers. The drug could not be detected in the blood plasma using a microbiological assay method during drinking water medication with the conventional dose (55 mg/1). An increase of the dose 10- to 50-fold resulted in average plasma concentrations of </= 1 microg/ml (variation < 0.1 - 2.6 microg/ml). In efficacy trials using an infection model with an E. coli strain with a minimal inhibitory concentration (M.I.C.) of 3.2 mug/ml a good therapeutic effect was observed when ampicillin trihydrate was given for 4 days at a concentration in the drinking water of at least 1.65 g/1.