Continuous sampling for determination of pharmacokinetics in rat cerebrospinal fluid

Abstract

A method for determining drug concentration relationships between plasma and cerebrospinal fluid (CSF) in rats is described. Continuous CSF samples were collected directly from the third anterior ventricle with an indwelling cannula inserted through the bregma point, and drug concentrations were determined by high-pressure liquid chromatography and radioimmunoassay iicromethods. Three antibiotics with different abilities to cross the blood-CSF barrier (chloramphenicol, piperacillin, and gentamicin) were tested. This method was found to be reproducible for each drug even if the antibiotic levels were low and the sample volumes very small. Peak CSF concentrations occurred between 0.75 and 1.25 h after injection for all three antibiotics. Percent penetration values at 1 h were 50, L2, and 5.4% for chloramphenicol, piperacillin, and gentamicin, respectively. Several techniques have been described for collecting cerebrospinal fluid (CSF) from various animals (13). In larger animals such as rabbits and dogs, continuous sampling of CSF in pharmacokinetic studies is done with a cannula implanted generally in the cisterna magna. The present report presents a simple, rapid cannulation technique for repeated sampling of CSF in rats. The CSF samples were collected directly from the third anterior ventricle with an indwelling cannula.This technique was tested and applied to study the pharmacokinetics in the CSF of three antibiotics from different families (chloramphenicol, piperacillin, and gentamicin) chosen for their varying ability to cross the blood-CSF barrier in mammalian species (2-4, 6). MATERIALS AND METHODSAnimals. Male Wistar rats (350 g) were anesthetized by intraperitoneal injection of urethane (1.25 g kg-1), and a catheter was inserted in the aortic arch by the carotid artery to allow blood sampling and antibiotic injection. The animals werte then placed on a stereotaxic table or in a surgical head holder. During deep anesthesia a subcutaneous injection of 2% Xylocaine was given locally. Five minutes later a hole was made in the skull at the bregma point (Fig. 1), and a cannula (1-mm external diameter) with a mandrel was placed into the third ventricle 6.5 mm under the brain surface. The mandrel was removed, and a needle (0.5-mm external diameter) was inserted into the cannula. This needle connected with polyethylene tubing to a peristaltic pump (Gilson) (flow rate, 2 ml min 1). Under these conditions, the CSF flow rate was 1 ,ul min 1 and was stable throughout the course of the experiment, which lasted 3 h. CSF was sampled every 15 min in small conical polypropylene tube (Ependorff). Arterial blood pressure was controlled and remained stable during the experiment.Monosuccinate sodium chloramphenicol (165 mg kg-1), piperacillin sodium (20 mg kg '), and gentamicin sulfate (20 mg kg-1) were injected in a bolus in the arterial catheter. * Corresponding author.High-pressure liquid chromatography assay. Concentrations of chloramphenicol and piperacillin in plasma and CSF samples were measured by high-pressure liquid...

Inhibition of NADH oxidation by chloramphenicol in the freely moving rat measured by picosecond time‐resolved emission spectroscopy

“…The increase in CAP concentration in brain tissue is a composite function of its hydrolysis rate, the excretion of CAP succinate, the glucuronidization into CAP glucuronide and the blood–brain barrier transfer. As the concentration of CAP into the cerebro‐spinal fluid of the rat injected with a 165‐mg/kg dose is 23 ± 5 mg/L during the first hour postinjection (Meulemans et al . 1986), in our experiments a 200‐mg/kg dose might lead to a CAP concentration around 26–28 mg/L (80–110 µ m ).…”

“…1997) and of multiresistant treatments (Barie 1998). Owing to its excellent accessibility to the cerebro‐spinal fluid and brain tissue, this antibiotic is incomparably efficient against meningitis and typhoid fever (Meulemans et al . 1986).…”

“…1993; Bories and Cravendi 1994). CAP presents, nevertheless, an unusual excellent accessibility to the cerebro‐spinal fluid and brain tissue where its accumulation may reach a concentration efficient enough to inhibit mitochondria respiration (Meulemans et al . 1986).…”

Chloramphenicol decreases brain glucose utilization and modifies the sleep–wake cycle architecture in rats

“…1984). The maximal CAP concentration in the cerebrospinal fluid is reached at 45 min and remains unchanged for 1 h (Meulemans et al . 1984, 1986).…”

Discovery and development of new antimicrobial agents

“…These tissue distribution studies define some potential advantages of azithromycin over the standard macrolide, erythromycin, and help with the design of clinical trials in humans (65). Among numerous other animal pharmacokinetic studies that have evaluated new antibiotics are studies to measure the penetration of azole antifungal compounds into the eyes of rabbits (139), models to study drug penetration into surgical wounds of dogs (133), and novel sampling methods to measure spinal fluid levels of antibiotics in rats (103).…”