Ceftazidime encephalopathy developed without the elevation of cerebrospinal fluid concentration of ceftazidime: A case report of two cases

Background: Ceftazidime encephalopathy is reported to be caused by the repeated administration of ceftazidime in patients with renal impairment because of the high serum concentration of ceftazidime. Ceftazidime encephalopathy has been considered to be caused by the elevation of the cerebrospinal fluid (CSF) concentration. However, as no reports have measured CSF concentrations, the relationship with ceftazidime encephalopathy and CSF concentration has not been clarified. Case presentation: Case 1: An 80-year-old Japanese man under a combination therapy with peritoneal dialysis and hemodialysis, who had been treated for a cellulitis with ceftazidime, developed altered consciousness and was diagnosed as ceftazidime encephalopathy. His serum concentration of ceftazidime was elevated, but CSF concentration was only under 0.1 μg/mL. Case 2: An 88-year-old Japanese man with chronic kidney disease, who had been treated for a urinary tract infection with ceftazidime, developed altered consciousness and was diagnosed as ceftazidime encephalopathy. His serum concentration of ceftazidime was elevated, but CSF concentration was within the therapeutic range. However, his serum and CSF concentration of quinolinic acid was markedly increased. Conclusions: Patients with renal failure are more likely to develop ceftazidime encephalopathy. We need to pay attention to the dosage of ceftazidime and to the appearance of neurological symptoms. Ceftazidime encephalopathy was considered to be caused by the high CSF concentration, but it could be caused by quinolinic acid as neurotoxic substance.