Comparative study of permeability into rat cerebrospinal fluid of the quinolones: dependency on their lipophilicities.

Pharmacokinetic behavior involved in the entry of four quinolone antibacterial agents, norfloxacin (NFLX), ciprofloxacin (CPFX), ofloxacin (OFLX) and nalidixic acid (NA), into cerebrospinal fluid (CSF) was comparatively investigated in rats. Periodically, after the bolus i.v. dose of each quinolone (10 mg/kg), aliquots of CSF were collected by cisternal puncture and blood samples were then withdrawn from the jugular vein. CSF and serum (total and unbound) levels of the drugs were determined by HPLC method. Transport parameters for three new quinolones (NFLX, CPFX, OFLX) into CSF were obtained by physiological model analysis. Serum levels of OFLX and NFLX declined bi-exponentially with time, whereas the serum levels of NA and CPFX declined in mono-exponential and tri-exponential fashion, respectively. Fractions of each quinolone unbound to serum protein (approximately 0.7 for NFLX, CPFX, and OFLX, 0.12 for NA) were almost the same at any point in time. The CSF levels of these quinolones rose quite rapidly after drug administration, and then declined, along with their serum levels. Both the CSF level and the ratio of CSF concentration to serum unbound concentration were the highest for NA, followed by OFLX, CPFX and NFLX. These values of the four quinolones were almost proportional to the apparent partition coefficient (Papp) between n-octanol and phosphate buffer (pH 7.0) values of each reported in a previous paper [Tsuji et al., Antimicrob. Agents Chemother., 32, 190 (1988)]. In the three new quinolones, OFLX had a larger value of apparent diffusional clearance between blood and CSF (PAc) than CPFX and NFLX.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic determination of nalidixic acid in rat serum, brain and cerebrospinal fluid.

A high-performance liquid chromatographic method for the determination of nalidixic acid (NA) in rat serum, brain and cerebrospinal fluid (CSF) was developed. NA in rat serum and brain homogenate was extracted and injected onto a reversed-phase column. CSF was directly analysed without extraction procedure. The limits of detection were 0.05 microgram ml-1 for serum, 0.07 microgram g-1 for brain and 0.02 microgram ml-1 for CSF, respectively. Calibration curves were linear over the concentration ranges 0.1-50 micrograms ml-1 for serum, 0.12-9 micrograms g-1 for brain and 0.05-10 micrograms ml-1 for CSF, respectively. The reproducibility of NA assay in rat biological media ranged from 1 to 4% relative standard deviations (RSD). The recoveries of NA added to serum and brain were higher than 96% with an RSD of less than 4%. The present method was found to be applicable to pharmacokinetic study of NA in rat serum, brain and CSF.

Penetration of pefloxacin into cerebrospinal fluid of patients with meningitis.

We evaluated the diffusion of pefloxacin into the cerebrospinal fluid (CSF) in 15 patients with bacterial meningitis or ventriculitis, 14 of whom were treated with other antibiotics. Three doses of pefloxacin were administered at 12-h intervals to 11 patients intravenously and to 4 patients orally. Individual doses were 7.5 mg/kg in seven patients and 15 mg/kg in eight patients. Plasma and CSF levels were determined by a high-performance liquid chromatographic assay. The concentrations of pefloxacin in CSF were measured 2 h after the third intravenous dose and 4 h after the third oral dose. In patients receiving 7.5 mg/kg, peak levels in plasma ranged from 6.8 to 16 micrograms/ml, and trough levels were from 2 to 7.5 micrograms/ml. Concentrations in CSF ranged from 2.4 to 9 micrograms/ml. In patients receiving 15 mg/kg, peak levels in plasma ranged from 14 to 18.6 micrograms/ml, and trough levels were from 4 to 13.2 micrograms/ml. Concentrations in CSF ranged from 6.5 to 13 micrograms/ml. These preliminary data indicate that pefloxacin diffuses well into the CSF of patients with inflamed meninges.