A SIMPLE HPLC ASSAY, WITH ULTRAVIOLET DETECTION, FOR DETERMINATION OFA MONOBACTAM ANTIBIOTIC

BMS-180680 is a monobactam antibiotic currently under development for the treatment of gram negative bacteria including Pseudomonas aerugino sa. Simple, rapid sensitive, precise, and reproducible assay methods h ave been developed for the quantification of BMS-180680 in dog and rat plasma using aztreonam as the internal standard. The assay methods in volve a single-step protein precipitation by addition of acetonitrile, followed immediately by centrifugation, after which the supernatant i s evaporated to dryness (65 degrees C) under a gentle stream of nitrog en. The residue is reconstituted in the mobile phase, transferred to a micro-WISP vial and injected on to a Zorbax R(x) C-18 HPLC column pre ceded by a guard column. Mobile phase comprised 17% acetonitrile and 8 3% of 40 mM dibasic ammonium phosphate and 6 mM tetrabutylammonium hyd rogen sulfate. A small amount of tetrahydrofuran (20 mL/liter of mobil e phase) was added and the apparent pH of the mobile phase was adjuste d to 4.1 with 85% phosphoric acid. The column eluate was monitored by an ultraviolet detector set at 252 nm. The nominal retention times wer e 8.0 and 9.0 min for aztreonam and BMS-180680, respectively. The lowe r limit of quantitation levels were 0.1 and 0.2 mu g/mL in dog and rat plasma respectively. The inter-assay and intra-assay precision values of the quality control (QC) samples were less than 6.4% relative stan dard deviation in both dog and rat plasma and the predicted concentrat ions of the QC samples deviated less than 10% of the corresponding nom inal values. BMS-180680 was stable in dog and rat plasma at -20 degree s C for at least 64 and 55 days, respectively and for at least three f reeze/thaw cycles in either dog or rat plasma. Both BMS-180680 and azt reonam were stable in the autosampler for at least 59 hours at the roo m temperature. The assays were employed to measure BMS-180680 concentr ations in heparinized dog and rat plasma samples obtained from a pharm acokinetic study.