The development and performance of a radioimmunoassay for the analysis of ZM 213,689, the major metabolite of meropenem—a carbapenem antibiotic—in plasma and urine

Abstract The development of a radioimmunoassay for the analysis of ZM 213, 689, the major metabolite of meropenem found in the plasma and urine of rat, dog and humans, is described. The assay is rapid in order to minimise the effect of degradation of meropenem to ZM 213,689 in biological samples and has a working range of 0.08–3.5 mg l −1 (RSD ⩽ 15%). The antibody was specific for ZM 213,689 with cross-reactivity to meropenem of only 0.4%. The synthesis of the immunogen and radiotracer involved a novel approach due to the multifunctional nature of ZM 213,689.