Enhanced bioavailability of oxolinic acid by ultra-fine size reduction in yellowtail.

Abstract

Effects of ultra-fine size reduction of oxolinic acid on the absorprion by yellowtail were studied by a high performance liquid chromatographic method. Under the high performance liquid chromatographic conditions using a fluorescent detector set for the determination of oxolinic acid in yellowtail tissues, oxolinic acid was well separated from the endogenous com-ponents of yellowtail and the limits of detection in the serum, liver, kidney and muscle were 0.01-0.03 μg/ml or g. After oral administration of the ultra-fine size oxolinic acid in a diet at 30mg/kg once a day for 5 days, the concentration of oxolinic acid in yellowtail tissues went below the limit of detection (0'01-0.03μg/ml or g) within 3 days in the serum, 10days in the liver, 16days in the kidney and 13days in the muscle. When pharmacokinetic parameters were compared between the ultra-fine (diameter=1.0μm) size and ordinary (diameter=6.4μm) preparation of oxolinic acid after single oral administration at 30mg/kg, these two types of oxolinic acid were almost equal in the time of peak serum concentrations, but the peak concentration and areas under the serum concentration-time curve of the ultra-fine size type was 1.7 and 1.3times higher than those of the ordinary type, respectively. Thus, the bioavailablity of oxolinic acid was enhanced by particle size reduction.