Lack of interference of five new beta-lactam antibiotics with serum creatinine determination.

Several cephalosporins falsely elevate creatinine concentration as determined by the Jaffé reaction. We studied the in vitro effect of various concentrations of cefoperazone, ceftizoxime, ceftriaxone, ceftazidime, and azthreonam on the creatinine determination in serum, using both a manual and an automated technique. No false elevation or change in baseline creatinine concentration could be observed with any of the five antibiotics. With the use of large concentrations in serum of these beta-lactam antibiotics, we can estimate their lack of interference with creatinine determination in urine as well. Therefore, there is no need to relate the timing of blood (and urine) sampling for creatinine assay to dosage of these antibiotics.