Cerebrospinal fluid ceftazidime kinetics in patients with external ventriculostomies

Ceftazidime has proven to be effective for the treatment of bacterial meningitis caused by multiresistant gram-negative bacteria. Since nosocomial central nervous system infections are often accompanied by only a minor dysfunction of the blood-cerebrospinal fluid (CSF) barrier, patients with noninflammatory occlusive hydrocephalus who had undergone external ventriculostomy were studied (n = 8). Serum and CSF were drawn repeatedly after the administration of the first dose of ceftazidime (3 g over 30 min intravenously), and concentrations were determined by high-performance liquid chromatography by using UV detection. The concentrations of ceftazidime in CSF were maximal at 1 to 13 h (median, 5.5 h) after the end of the infusion and ranged from 0.73 to 2.80 mg/liter (median, 1.56 mg/liter). The elimination half-lives were 3.13 to 18.1 h (median, 10.7 h) in CSF compared with 2.02 to 5.24 h (median, 3.74 h) in serum. The ratios of the areas under the concentration-time curves in CSF and serum (AUC(CSF)/AUC(S)) ranged from 0.027 to 0.123 (median, 0.054). After the administration of a single dose of 3 g, the maximum concentrations of ceftazidime in CSF were approximately four times higher than those after the administration of 2-g intravenous doses of cefotaxime (median, 0.44 mg/liter) and ceftriaxone (median, 0.43 mg/liter) (R. Nau, H. W. Prange, P. Muth, G. Mahr, S. Menck, H. Kolenda, and F. Sorgel, Antimicrob. Agents Chemother, 37:1518-1524, 1993). The median AUC(CFS)/AUC(S) ratio of ceftazidime was slightly below that of cefotaxime (0.12), but it was 1 order of magnitude above the median AUC(CSF)/AUC(S) of ceftriaxone (0.007) (Nau et al., Antimicrob. Agents Chemother. 37:1518-1524, 1993). The concentrations of ceftazidime observed in CSF were above the MICs for most Pseudomonas aeruginosa strains. However, they are probably not high enough to be rapidly bactericidal. For this reason, the daily dose should be increased to 12 g in cases of P. aeruginosa infections of the central nervous system when the blood-CSF barrier is minimally impaired.