Clinical pharmacology of oxolinic acid in young dairy calves.

The in vitro sensitivity to oxolinic acid shown by pathogenic gram-negative bacterial isolates from young calves with diarrhea, pneumonia, and septicemia was investigated by the bute dilution method. Minimal bactericidal concentrations of the drug for 65.5% of the isolates were less than or equal to 1.56 mug/ml and for 90%, less than or equal to 6.25 mug/ml. Cross resistance between oxolinic acid and chloramphenicol, streptomycin, neomycin, colistin, ampicillin, gentamicin, and oxytetracycline was not observed. Oxolinic acid was orally administered to a group of calves at dose levels of 12.5 to 57.0 mg/kg, and sodium oxolinate was intramuscularly injected in another group of calves at dose levels of 12.5 and 20 mg/kg. In the 1st group, oxolinic acid was detected in blood serum 15 minutes later; peak serum concentrations averaged 25 mug/ml at 10 hours after treatment with 50 mg of the drug/kg and 3 mug/ml at 7 hours, with 12.5 mg of the drug/kg. In the 2nd group, the dose level of 20 mg of sodium oxolinate/kg resulted in mean peak serum concentration of 4 mug/ml, observed 1 hour after the drug was injected. The half-life of the drugs in serum was approximately 3.5 hours after they were orally or intramuscularly given. These investigations indicate that oxolinic acid could be used in the treatment of the common calf diseases.