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 less than 1 microgram of HR 810 per 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 intramuscular dose. The peak concentration of HR 810 was 51.2 +/- 8.0 micrograms/ml at 1 h postdose. The half-life of the absorption phase (mean +/- standard deviation) was 0.35 +/- 0.10 h, and the half-life of the elimination phase was 0.75 +/- 0.06 h. This is 54% less than the half-life of elimination of 1.38 h previously reported for the intravenous dose.