Abstract
A microbiological assay procedure and high-performance liquid-chromatography (HPLC) procedure have been developed for determining grepafloxacin (GPFX) in human plasma and urine.
In the bioassay method drug concentrations were determined by the thin-layer cup method, using Bacillus subtilis ATCC6633 as the test strain and nutrient agar as the test medium. Calibration curves of GPFX were made in human plasma and 1/15M phosphate buffer (P. B.) pH 7.4 for plasma samples and in 1/15M P. B. pH 7.0 for urine samples. The lowest detectable concentration of GPFX by the method was 0.012-0.025 μg/ml.
In HPLC GPFX was extracted from plasma and urine by chloroform. The extracts were analyzed using a reverse-phase analytical column and detected by the fluorescence method. The intra-assay coefficient of variation for plasma was less than 4.6% at 0.01-1.00, μg/ml and less than 3.5% at 0.025-5.00 μg/ml, whereas for diluted urine it was less than 4.0% at 0.25-50.00 μg/ml. Plasma and urine samples in phase I studies were analyzed by HPLC and the bioassay method. A good corelation was observed between them.
