HIGH-PRESSURE LIQUID-CHROMATOGRAPHIC ASSAY AND PHARMACOKINETICS OF HR-810 AFTER INTRAMUSCULAR INJECTION IN RABBITS

A high-pressure liquid chromatographic assay was developed for the detection of HR 810 in rabbit plasma. There was no interference in the high-pressure liquid chromatographic assay from other antibiotics. The method was accurate, reproducible and capable of detecting < 1 .mu.g of HR 810/ml in plasma. The assay correlated with the microbiological assay (correlation coefficient, 0.93) and was used to quantitate the concentration of HR 810 in rabbit plasma and determine its half-life subsequent to a 20 mg/kg i.m. dose. The peak concentration of HR 810 was 51.2 .+-. 8.0 .mu.g/ml at 1 h postdose. The half-life of the absorption phase (mean .+-. SD) was 0.35 .+-. 0.10 h and the half-life of the elimination was 0.75 .+-. 0.06 h. This is 54% less than the half-life of elimination of 1.38 h previously reported for the i.v. dose.