[Microbiological assay method of BMY-28100 and some other cephem antibiotic in serum and tissues. Development of new sample preparation with Evan's blue, a high albumin binding dye].

With a new simple sample pretreatment, microbiological assay methods for quantitative determination of BMY-28100 and some other cephem antibiotics in serum and tissues have been developed. Presented sample pretreatment was founded on the extraction with Evans' blue, a high serum protein binding dye, and the ultrafiltration using cellulose membrane (Millipore; MW cutoff is 10,000) to which Evans' blue was specifically absorbed. Regardless of sample media, antibiotic contents in filtrates were determined accurately using calibration curves based on standard solutions prepared with 1/15 M phosphate buffer, pH 7.4. Four cephems, ceftriaxone (CTRX), cefazolin (CEZ), BMY-28100 and cefadroxil (CDX) were examined in human serum and rat liver tissues. Corrections were made for antibiotic recoveries into 1/15 M phosphate buffer, pH 7.4. CTRX, CEZ, BMY-28100 and CDX in serum and tissues were recovered into buffer at rates of 98.4-101.6%, 97.6-102.0%, 99.8-101.4% and 97.5-98.2% of of spiked (theoretical) values, respectively regardless of antibiotic concentrations. Furthermore, these concentrations obtained using the present bioassay method were well in agreement with those obtained by the HPLC method. When BMY-28100 was administered to volunteers, concentrations of BMY-28100 in serum obtained by the present bioassay method were well in agreement with those obtained by the usual bioassay method which required the fresh human serum to prepare the standard solutions.