Cephaloglycin, cephalothin, cephaloridine, cefoxitin, and cephacetrile are cephalosporin antibiotics that react with alkaline picrate solution to give a creatinine-like response. The mechanism of this reaction is not known, and several structurally similar compounds do not react under these same conditions. Because large quantities of a cephalosporin antibiotic may be administered to a patient with limited ability to excrete the drug (as occurs with compromised renal function), the magnitude of this interference can be appreciable. It does not appear possible to avoid the cephalosporin-caused interference by the use of "kinetic" creatinine methods.