Raymond F. Koss

Pharmacokinetic model for nalidixic acid in man III. Effect of repeated oral dosage

Abstract In studies which involved the administration of 1-Gm. doses of nalidixic acid to human volunteers four times daily for a period of 10days, it has been shown that the resulting plasma levels of nalidixic and of hydroxynalidixic acid could be predicted reasonably well from a model derived from single-dose studies. More satisfactory blood levels are obtained if the doses are taken at least 1hr. before meals. Repeated dosage results in no important change in the absorption-excretion-metabolism patterns of the drug.

High-performance liquid chromatographic analysis of roxoxacin and its N-oxide metabolite in plasma and urine

Abstract A high-pressure liquid chromatographic methoc for the analysis of rosoxacin and its pyridyl N-oxide metabolite in plasma and urine extracts is described. A statistical evaluation of the assay data has shown acceptable accuracy and precision for 0.5 to 25 μg of rosoxacin or the metabolite per ml of plasma and for 2.5 to 60 μg/ml of either compound in urine. The minimum quantifiable level for rosoxacin was 0.13 μg/ml in plasma and 0.64 μg/ml in urine; for the metabolite in plasma and urine, the corresponding values were 0.21 and 0.60 μg/ml, respectively. The method was applied to plasma and urine from three dogs medicated orally with 5 mg/kg of rosoxacin. The pharmacokinetic parameters calculated for rosoxacin were: plasma half-life, 1.9 h; plasma clearance, 65 ml/min; volume of distribution, 11.31. The average total urinary excretion of resoxacin as free and conjugated rosoxacin and its free N-oxide was 7.7 ± 0.2% over the 48-h collection period.