Cerebro-spinal fluid

The drug is metabolized rapidly in the liver, kidney, intestinal mucosa, and even red blood cells. Therefore it has a plasma half-life of only 10 min after bolus intravenous application. The major metabolite, uracil arabinoside (ara-U), can be detected in the blood shortly after cytarabine administration. About 80% of the dose is excreted in the urine within 24 h, with less than 10% appearing as cytarabine the remainder is ara-U. After continuous infusion, cytarabine levels in the liquor (cerebro-spinal fluid) approach 40% of that in plasma. Continuous infusion schedules allow maximal efficiency, with uptake peaks of 5-7 pM. It can be administered intrathecally as an alternative to methotrexate. 

While levels of endrin or endrin metabolites can be measured in tissue and excreta, thereby serving as biomarkers of exposure, the analytical techniques required are somewhat sophisticated and non-routine. Further, measurements of endrin in blood are best suited for detecting recent exposures because endrin is cleared rapidly from blood. The lack of persistence of endrin in human tissues and blood seen in the study of Coble et al. (1967) indicates a brief half-life for endrin on the order of 1-2 days. Sera levels of endrin (time to sample not specified) in Pakistani patients who were poisoned with endrin ranged from 0.3 to 254 ppb (0.3-254 pg/L) survivors had sera levels that ranged from 1.3 to 17.4 ppb (1.3-17.4 pg/L) (Rowley et al. 1987). An endrin concentration of 0.3 ppb was detected in the cerebro-spinal fluid. 

McNay EC, Sherwin RS. 2004. From artificial cerebro-spinal fluid (acsf) to artificial extracellular fluid (aecf) microdialysis perfusate composition effects on in vivo brain ecf glucose measurements. J Neurosci Methods 132(1) 35-43. 

It would be helpful if there were a peripheral measure of neurotransmitter function that could be used to guide medication selection and dosing, but unfortunately this has not yet been developed. Some measures can be obtained from the cerebro spinal fluid, but even these levels have not been established as a guide to treatment. Peripheral measures or related measures of neuroendocrine function (Birmaher et ah, 2000) may some day be useful guides. Likewise, pharmacogenetics may help select the most appropriate medication and dosage (Anderson and Cook, 2000, Chapter 7 in this volume). 

Intrathecal A form of intraspinal anaesthesia or analgesia in which the agent is injected through the dura mater and arachnoid membrane into the cerebro-spinal fluid which surrounds the spinal cord. 

Notes. SAR—Structure activity relationship CL-clearance CSF-cerebro,spinal fluid TBI-traumatic brain injury. 

The anaesthetic is injected into the subarachnoid space via a lumbar puncture between vertebrae L2 and L3 or L3 or L4. This places the anaesthetic in the cerebro-spinal fluid. Efferent nerves (motor and sympathetic) and afferent fibres (sensory) are affected by the local anaesthetic. This method carries a risk of damage to the spinal cord. 

Stabenau IR, Warren KS, Rail DP. 1958. The role of pH gradient in the distribution of ammonia between blood and cerebro-spinal fluid, brain and muscle. J Clin Invest 38 373-383. 

Fig. 1. Cyclic voltammograms obtained with a carbon microelectrode in the cerebro spinal fluid of an anaethetized rat (a) before and (b) after electrical stimulation. (After Wightman et al. [3].)...

It was not until the mid-1970s that microelectrodes were first successfully used to study the voltammetric behaviour of molecules in vivo. This first study by Wightman et al. [3] involved the monitoring of the release of electroactive species into the cerebro spinal fluid of an anaesthetized rat following the electrical stimulation of the substantia nigra, a process known to release homovanillic acid, a metabolite of dopamine. A carbon fibre microelectrode was placed in the cerebro spinal fluid and a saturated calomel electrode, and a secondary electrode, were placed nearby. Cyclic vol-tammograms before and after stimulation were then recorded and, as shown in Fig. 1, an oxidation current at around + 0.8 V, which was attributed to the oxidation of the homovanillic acid, was observed after stimulation. 

Pharmacokinetics The drug is used parenterally and with slow intravenous infusion may reach appreciable levels in the cerebro.spinal fluid. Ara-C is eliminated via hepatic metabolism. 

Osuna E, Perez-Carceles MD, Luna A, Pounder DJ (1992) Efficacy of cerebro-spinal fluid biochemistry in the diagnosis of brain insult. Forensic Sci Int 52 193-198... 

A lumbar puncture was carried out successfully and samples of cerebro spinal fluid taken for analysis. Dr Mitchell then read out aloud the name of the patient, the drug and the dose from the label on the first syringe and then handed it to Dr North. Dr Mitchell did not, however, read out the route of administration. Dr North, having received the syringe, now asked if the drug was Cytosine, which Dr Mitchell confirmed. Dr North then removed the cap at the bottom of the syringe and screwed it onto the spinal needle after which he injected the contents of the syringe. 

Levels of VIP and CCKs in the Cerebro-spinal Fluid S of Schizophrenic and Control Patients Obtained following Reverse-Phase HPLC ... 

A. Bard In extending what you have been saying to other types of tissues, such as blood stream or heart muscle, one starts to find rather serious problems about adsorption of proteins onto the electrode and deactivation is the cerebro-spinal fluid a particularly good medium ... 

R. M. Wightman Cerebro-spinal fluid and the extracellular fluid, both are very protein free from a biological point of view and, so, they help a great deal in making such measurements. The fact that we can make these measurements does not mean that you can make direct measurements in blood that is a lot more complicated and a lot more hostile environment ... 

Jaup BH, Bloomstrand CH. Cerebro-spinal fluid concentration of pirenzepine after therapeutic dosage. Scand J Gastroenterol 1980 15 35. 

TABLE 2 - Latency and intensity of SYS in cats after injection of into different areas of cerebro-spinal fluid. 

In human secretions other than urine, urea is present in the following percentages cerebro-spinal fluid, 0-2-0-4 saliva, 0-09-0-4 milk, O-O8-O 10 bile, 0-18-0-4. 

As Barcroft has shown, the freedom of human life, as expressed in repose and action, requires constancy in the composition of the blood and the cerebro-spinal fluid, while the stability of the internal environment as a whole requires inter-dependent mechanisms for storage, distribution and removal of solutes. Transitory changes in the blood due to metabolic activity are compensated for by si)ecially adapted systems for neutralisation, detoxication, and pulmonary and renal excretion, and form part of the routine physiological activities of life. Excessive changes in the blood composition are the result of pathological processes, resulting in abnormal metabolism or in defective compensation and excretory dysfunction. 

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