MONITORING OF PEFLOXACIN SERUM CONCENTRATIONS IN INTENSIVE-CARE UNIT PATIENTS - COMPARISON OF A NEW IMMUNOASSAY WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Serum quinolone concentrations are not routinely measured in clinical practice. However, in order to optimize quinolone treatment, monitorin g of serum concentrations could sometimes be useful particularly in cr itically ill patients. A new enzyme-linked immunosorbent assay (ELISA) that permits direct determination of pefloxacin in serum is described . To validate this new assay, pefloxacin concentrations were measured in 314 serum samples from 74 intensive care unit patients treated with pefloxacin (400 mg i.v. twice daily). Reference concentrations were o btained by reverse phase high-performance liquid chromatography (HPLC) with spectrofluorometric detection. Results showed that concentration s measured by ELISA correlated very well with those by HPLC (r = 0.957 ; y = 1.03 and x - 0.15). In this population, the concentrations found by ELISA varied between individuals (C(min) = 0.70-39 mug/ml; C(max) = 5.2-40 mug/ml). However, 86% of the measured C(max) and C(min) level s were adequate for optimal pefloxacin therapy. Only 11% of C(min) and 14% of C(max) were below the optimal values (i.e., 2 and 8 mug/ml, re spectively). These results suggest that despite the large therapeutic index of pefloxacin, monitoring of its serum concentrations using a ra pid ELISA technique may be useful for optimal antimicrobial treatment of certain intensive care unit patients.