Water medication of a swine herd with amoxycillin

A swine herd, consisting of 201 swine, was treated with amoxycillin. Amoxycillin was administered in the water system for 5 days, at a mean dose of 23 mg/kg body weight per day. Twice a day the water consumption was monitored, and blood samples collected from 10 randomly selected pigs. The plasma concentration of amoxycillin was measured by use of high performance liquid chromatography (HPLC). Three days after initiating amoxycillin treatment, the plasma concentration reached a constant level, at which it varied between a maximum of 1.3 micrograms/mL and a minimum of 0.5 microgram/mL. The plasma concentration was compared with a predicted curve based on pharmacokinetic variables obtained previously. The plasma concentrations were at the same level as the simulated ones. The minimum inhibitory concentration (MIC) values of the common respiratory pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida are about 0.1 microgram/mL. In pigs the distribution between bronchial mucosa and plasma (AUCmucosa/AUCplasma) is 0.3, which indicates a therapeutic plasma concentration of 0.3 microgram/mL. Data from the present study indicates that water medication with amoxycillin is effective as follow-up treatment.