The development and validation of a novel LC-MS/MS method for the quantification of cenicriviroc in human plasma and cerebrospinal fluid.

A high-performance liquid chromatography tandem mass spectrometric method was developed and validated for cenicriviroc (CVC) quantification in human plasma and cerebrospinal fluid (CSF). The method involved precipitation with acetonitrile and injecting supernatants onto the column. Separation was achieved on an XBridge C18 column with a gradient elution of 0.1% formic acid in water and acetonitrile. Analyte detection was conducted in positive ion mode using selected reaction monitoring. The m/z transitions were: CVC (697.3 → 574.3) and CVC-d7 (704.4 → 574.3). Calibration curve ranged from 5 to 1000 ng/mL for plasma and from 0.241 to 15.0 ng/mL for CSF. The intra- and inter-day precision and accuracy were <15% for both plasma and CSF across four different concentrations. CVC recovery from plasma and artificial CSF was >90%. The method was utilized for the measurement of patients' plasma and CSF samples taking a dose of 50, 150 and 300 mg q.d.

Rapid determination of piracetam in human plasma and cerebrospinal fluid by micellar electrokinetic chromatography with sample direct injection.

A simple micellar electrokinetic chromatography (MEKC) method with UV detection at 200 nm for analysis of piracetam in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of piracetam from biological matrix was performed at 25 degrees C using a background electrolyte consisting of Tris buffer with sodium dodecyl sulfate (SDS) as the electrolyte solution. Several parameters affecting the separation of the drug from biological matrix were studied, including the pH and concentrations of the Tris buffer and SDS. Under optimal MEKC condition, good separation with high efficiency and short analyses time is achieved. Using imidazole as an internal standard (IS), the linear ranges of the method for the determination of piracetam in plasma and in CSF were all between 5 and 500 microg/mL; the detection limit of the drug in plasma and in CSF (signal-to-noise ratio=3; injection 0.5 psi, 5s) was 1.0 microg/mL. The applicability of the proposed method for determination of piracetam in plasma and CSF collected after intravenous administration of 3g piracetam every 6h and oral administration 1.2g every 6h in encephalopathy patients with aphasia was demonstrated.

Histamine metabolites in cerebrospinal fluid of patients with chronic schizophrenia: their relationships to levels of other aminergic transmitters and ratings of symptoms.

Levels of the histamine metabolites, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), and metabolites of other aminergic transmitters and of norepinephrine were measured in cerebrospinal fluid of 36 inpatients with chronic schizophrenia and eight controls. The mean t-MH level from controls was nearly identical to the levels seen previously in healthy volunteers. Compared with controls, the mean level of t-MH in the schizophrenic patients was 2.6-fold higher (p = 0.006); 21 of the patients had levels exceeding the range of controls. There was no significant difference (p > 0.05) in levels of other analytes, although the levels of t-MH correlated significantly with those of t-MIAA, homovanillic acid, 3,4-dihydroxyphenylacetic acid, norepinephrine, 3-methoxy-4-hydroxyphenylglycol and 5-hydroxyindoleacetic acid. The difference in levels of t-MH were not attributable to medication, since those taking (n = 10) or withdrawn from (n = 26) neuroleptic drugs had nearly the same mean levels of t-MH; each group had higher levels than controls (ANOVA: p < 0.05). Patients with or without tardive dyskinesia showed no significant differences in means of any analyte. Only levels of t-MH among those with schizophrenia correlated with positive symptom scores on the Psychiatric Symptom Assessment Scale (rs = 0.45, p < 0.02). The elevated levels of t-MH in cerebrospinal fluid, which represent histamine that was released and metabolized, suggest increased central histaminergic activity in patients with chronic schizophrenia.

pros-Methylimidazoleacetic acid in cerebrospinal fluid of patients with chronic schizophrenia: relationships to ratings of symptoms, ventricular brain ratios, and rates of urine excretion.

Concentrations of pros-methylimidazoleacetic acid (p-MIAA) were measured in cerebrospinal fluid of 30 patients with chronic schizophrenia. Levels of p-MIAA correlated negatively with mean scores of the Psychiatric Symptom Assessment Scale for positive symptoms (r = -0.48), but not negative symptoms, and with ventricular brain ratios (r = -0.48). Patients with abnormal ventricular enlargements had much lower concentrations of p-MIAA than those with normal ventricles. These results suggest that processes that reduce accumulation of p-MIAA in CSF may be associated with increased severity of symptoms among patients with chronic schizophrenia.

High-performance liquid chromatographic determination of histamine in biological samples: the cerebrospinal fluid challenge--a review.

Histamine, a neurotransmitter crucially involved in a number of basic physiological functions, undergoes changes in neuropsychiatric disorders. Detection of histamine in biological samples such as cerebrospinal fluid (CSF) is thus of clinical importance. The most commonly used method for measuring histamine levels is high performance liquid chromatography (HPLC). However, factors such as very low levels of histamine, the even lower CSF-histamine and CSF-histamine metabolite levels, especially in certain neuropsychiatric diseases, rapid formation of histamine metabolites, and other confounding elements during sample collection, make analysis of CSF-histamine and CSF-histamine metabolites a challenging task. Nonetheless, this challenge can be met, not only with respect to HPLC separation column, derivative reagent, and detector, but also in terms of optimizing the CSF sample collection. This review aims to provide a general insight into the quantitative analyses of histamine in biological samples, with an emphasis on HPLC instruments, methods, and hyphenated techniques, with the aim of promoting the development of an optimal and practical protocol for the determination of CSF-histamine and/or CSF-histamine metabolites.

Development and validation of a sample stabilization strategy and a UPLC-MS/MS method for the simultaneous quantitation of acetylcholine (ACh), histamine (HA), and its metabolites in rat cerebrospinal fluid (CSF).

A UPLC-MS/MS assay was developed and validated for simultaneous quantification of acetylcholine (ACh), histamine (HA), tele-methylhistamine (t-mHA), and tele-methylimidazolacetic acid (t-MIAA) in rat cerebrospinal fluid (CSF). The biological stability of ACh in rat CSF was investigated. Following fit-for-purpose validation, the method was applied to monitor the drug-induced changes in ACh, HA, t-mHA, and t-MIAA in rat CSF following administration of donepezil or prucalopride. The quantitative method utilizes hydrophilic interaction chromatography (HILIC) Core-Shell HPLC column technology and a UPLC system to achieve separation with detection by positive ESI LC-MS/MS. This UPLC-MS/MS method does not require extraction or derivatization, utilizes a stable isotopically labeled internal standard (IS) for each analyte, and allows for rapid throughput with a 4 min run time. Without an acetylcholinesterase (AChE) inhibitor present, ACh was found to have 1.9±0.4 min in vitro half life in rat CSF. Stability studies and processing modification, including the use of AChE inhibitor eserine, extended this half life to more than 60 min. The UPLC-MS/MS method, including stabilization procedure, was validated over a linear concentration range of 0.025-5 ng/mL for ACh and 0.05-10 ng/mL for HA, t-mHA, and t-MIAA. The intra-run precision and accuracy for all analytes were 1.9-12.3% CV and -10.2 to 9.4% RE, respectively, while inter-run precision and accuracy were 4.0-16.0% CV and -5.3 to 13.4% RE, respectively. By using this developed and validated method, donepezil caused increases in ACh levels at 0.5, 1, 2, and 4h post dose as compared to the corresponding vehicle group, while prucalopride produced approximately 1.6- and 3.1-fold increases in the concentrations of ACh and t-mHA at 1h post dose, respectively, compared to the vehicle control. Overall, this methodology enables investigations into the use of CSF ACh and HA as biomarkers in the study of these neurotransmitter systems and related drug discovery efforts.

Identification and determination of 1-methylimidazole-4-acetic acid in human cerebrospinal fluid by gas chromatography-mass spectrometry.

A method for the quantification of 1-methylimidazole-4-acetic acid in human CSF was developed. Methylimidazole-acetic acid was identified and quantitated in CSF. The method involves concentration of the compound on a cation exchanger, extraction of the methyl ester with ethyl acetate, and preparation of a heptafluorobutyryl derivate of the methyl ester, which is finally purified by chromatography on silica gel and quantitated by gas chromatography-mass spectrometry with the deuterated analogue as internal standard. The coefficient of variation at 1 ng/ml was 13%. The limit of sensitivity was about 0.2 ng/ml. The concentration of methylimidazole-acetic acid in lumbar CSF from healthy volunteers was below 1 ng/ml. Ventricular CSF contained higher concentrations than lumbar fluid. The existence of a rostrocaudal concentration gradient was established. There was a correlation between the concentration of methylimidazole-acetic acid and tele-methylhistamine in CSF. The concentration of methylimidazole-acetic acid in lumbar CSF from schizophrenic patients, patients with subarachnoidal haemorrhage, or patients with rheumatic disease was in the range of that in healthy volunteers.

Presence and measurement of methylimidazoleacetic acids in brain and body fluids.

N tau-Methylimidazoleacetic acid, the histamine metabolite, and its isomer, N pi-methylimidazoleacetic acid, were demonstrated and measured in rat brain and in human cerebrospinal fluid, urine, and plasma by a gas chromatographic-mass spectrometric method that is simple and specific with a detection limit of about 7 pmol (i.e. 1 ng). The acids were separated in biological samples by ion exchange chromatography, derivatized as n-butyl esters with boron trifluoride-butanol, and extracted with chloroform. Complete chemical ionization mass spectra and mass ion abundance ratios established the identity of N tau - and N pi - methylimidazoleacetic acids in the biological extracts and of imidazoleacetic acid in urine, but not in cerebrospinal fluid, plasma, and brain. The methylimidazoleacetic acids as n-butyl esters were quantified by electron impact selected ion monitoring of m/e 95 esters at different retention times. 3-Pyridylacetic acid was used as an internal standard and monitored at m/e 93. The levels of N tau-methylimidazoleacetic acid and N pi-methylimidazoleacetic acid were, respectively (picomoles/g or picomoles/ml +/- S.E.), for brain, 373, 19 +/- 13.08 and 110.33 +/- 12.44; for cerebrospinal fluid, 22.77 +/- 2.15 and 80.76 +/- 18.92; and for plasma, 84.57 +/- 13.64 and 73.64 +/- 14.50. In urine, the respective levels were 20.75 +/- 1.30 and 73.02 +/- 38.22 nmol/mg of creatinine. The origin of N pi-methylimidazoleacetic acid is not certain.

Rostral-caudal concentration gradients of histamine metabolites in human cerebrospinal fluid.

The metabolites of histamine, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), have a large concentration gradient between cisternal and lumbar CSF in the rhesus monkey. The possibility of a t-MH and/or t-MIAA gradient in man was studied in sequential samples of CSF withdrawn from the lumbar space from a healthy male. The mean levels of t-MH and t-MIAA in the 14-16 ml segment of CSF from 6 male volunteers was also measured. pros-Methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not derived from histamine, was also measured. Levels of t-MH, t-MIAA and p-MIAA were measured by gas chromatography-mass spectrometry. With increasing volumes of CSF removed, t-MH and t-MIAA levels increased linearly (p less than 0.01) when plotted against the midpoints of each volume segment. Levels of t-MH and t-MIAA from the volunteers showed little variation; the means of the levels were within 15% of the respective regression lines of the points from the single subject. In contrast, p-MIAA levels showed no gradient (p greater than 0.6) in serially removed CSF; the individual levels in CSF from the volunteers on unrestricted diets varied widely, suggestive of a dietary influence on p-MIAA levels in the CNS. The concentration gradient of histamine metabolites in CSF confirms the rostral-caudal gradient observed in monkey and argues against plasma or spinal cord as major sources of these metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Diurnal fluctuation in levels of histamine metabolites in cerebrospinal fluid of rhesus monkey.

In samples of ventricular cerebrospinal fluid (CSF) that were collected from a conscious, restrained rhesus monkey at intervals of 30 90 min, levels of the histamine metabolites, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), were determined by gas chromatography-mass spectrometry. Levels of t-MH and t-MIAA each showed time-related fluctuations. Peak and trough concentrations of t-MIAA, the product of t-MH, paralleled, but lagged about 2 h behind, the levels of t-MH. Within the first 3 h of illumination, metabolite levels increased more than 3-fold; they fell sharply within the first 3 h of darkness. Mean levels of t-MH and t-MIAA were significantly higher during periods of illumination than of darkness. Fluctuations in the levels of pros-methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not a histamine metabolite, were markedly different from those of t-MH or t-MIAA; p-MIAA levels peaked only at the middle of the dark period. The time-related fluctuations in levels of t-MH and t-MIAA, but not p-MIAA, are similar to the daily rhythmic changes observed in monkey CSF for the levels of other central neurotransmitters and peptide neurohormones.

Histamine metabolites in cerebrospinal fluid of the rhesus monkey (Macaca mulatta): cisternal-lumbar concentration gradients.

Similar to metabolites of other aminergic transmitters, histamine metabolites of brain, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), could have a concentration gradient between rostral and caudal sites of CSF. To test this hypothesis, cisternal and lumbar CSF samples were collected in pairs from eight monkeys (Macaca mulatta), and levels of t-MH and t-MIAA were measured by gas chromatography-mass spectrometry. pros-Methylimidazoleacetic acid (p-MIAA), an endogenous isomer of t-MIAA that is not a histamine metabolite, was also measured. Cisternal levels (in picomoles per milliliter, mean +/- SEM) of t-MH (9.9 +/- 1.4) and t-MIAA (40.8 +/- 7.6), but not of p-MIAA (9.7 +/- 1.2), exceeded those in lumbar CSF (t-MH, 1.8 +/- 0.3; t-MIAA, 6.8 +/- 0.9; p-MIAA, 8.6 +/- 0.6) in every monkey. The magnitudes of the mean cisternal-lumbar concentration gradients for t-MH (6.6 +/- 1.1) and t-MIAA (6.5 +/- 1.3) were indistinguishable. These gradients exceed those of metabolites of most other transmitters. There was no gradient for the levels of p-MIAA. The cisternal, but not lumbar, levels of t-MH and t-MIAA were correlated. There was no significant difference between the means of the metabolite concentration ratios (t-MIAA/t-MH) in cisternal (4.0 +/- 0.4) and lumbar (4.4 +/- 0.9) CSF. The steepness of these gradients suggests that levels of t-MH and t-MIAA in lumbar CSF might be useful probes of histaminergic metabolism in brain.

Elevated levels of histamine metabolites in cerebrospinal fluid of aging, healthy humans.

The metabolites of histamine, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), were measured in lumbar cerebrospinal fluid of healthy, normal volunteers aged 20-31 (n = 4) and 60-72 (n = 8) by gas chromatography-mass spectrometry. Mean levels (pmol/ml) of t-MH, t-MIAA and the sum of t-MH and t-MIAA (2.9, 6.4 and 9.4, respectively) were significantly higher in CSF from older subjects than from younger subjects (1.1, 4.5 and 5.5, respectively). Another older subject had yet higher levels of metabolites (6.7, 15.1 and 21.8, respectively). The sum of the levels of the known metabolites of histamine in brain, i.e. t-MH and t-MIAA, did not overlap between the younger and older subjects. The levels of pros-methylimidazoleacetic acid, an endogenous isomer of t-MIAA that is not derived from metabolism of histamine, did not differ significantly between the two groups. These findings contrast with results of similar studies of metabolites of other aminergic transmitters in showing elevated levels of metabolites of histamine in cerebrospinal fluid with increasing age.

Cimetidine, but not oxmetidine, penetrates into the cerebrospinal fluid after a single intravenous dose.

1 Thirty-six patients with various neurological diseases or symptoms received single intravenous doses of either cimetidine 400 mg (n = 19) or oxmetidine 200 mg (n = 17), 15 or 60 min before a diagnostic lumbar puncture. 2 In the 15 min CSF samples concentrations of cimetidine were detectable but not measurable in 5 and non-detectable in 3 patients. 3 In the 60 min CSF samples the concentrations of cimetidine were detectable in all 11 patients and were measurable in 8 of these patients with a mean +/- s.e. mean of 0.12 +/- 0.01 microgram/ml. These CSF concentrations were correlated to simultaneously measured plasma concentrations (P less than 0.01). The mean ratio CSF/plasma concentration was 0.03. 4 No detectable concentrations of oxmetidine were found either in the 15 min (n = 9) or in the 60 min (n = 8) liquor samples. 5 Cimetidine penetrates the blood-drain barrier slowly and not freely after a single dose. Our data suggest that the new histamine H2-receptor antagonist oxmetidine does not cross this barrier.

Histamine metabolites and pros-methylimidazoleacetic acid in human cerebrospinal fluid.

In cerebrospinal fluid, levels of the histamine metabolites, tele-methylhistamine and tele-methylimidazole-acetic acid, were higher in elderly than in young people, and women had higher levels than men. Therefore, age and gender should be considered in studies of histamine metabolites as exemplified by their measurements in cerebrospinal fluid of patients with Huntington's disease. Levels of pros-methylimidazoleacetic acid, an isomer of tele-methylimidazoleacetic acid and not a metabolite of histamine, were higher in cerebrospinal fluid of men than of women. Levels of pros-methylimidazoleacetic acid in cerebrospinal fluid were highly positively correlated with the severity of Parkinson's disease in a group of non-medicated, mildly to moderately affected patients.

Presence and measurement of imidazoleacetic acid, a gamma-aminobutyric acid agonist, in rat brain and human cerebrospinal fluid.

Imidazoleacetic acid (IAA) was unequivocally demonstrated in rat brain, human CSF, and human plasma by a gas chromatographic-mass spectrometric method that can reliably quantify as little as 8 pmol, i.e., 1 ng. Owing to tautomerism of the imidazole ring, IAA and [15N, 15N]IAA, the internal standard, each formed two chromatographically distinct isomers after derivatization of the ring nitrogens with either ethyl chloroformate or methyl chloroformate. The isomers of n-butyl(N-ethoxycarbonyl)imidazole acetate and n-butyl(N-methoxycarbonyl)imidazole acetate were identified by analysis with methane chemical ionization and electron impact ionization of molecular and fragment ions. The levels (mean +/- SEM) of free IAA were 140 +/- 14 pmol/g and 2.7 +/- 0.2 pmol/ml in brains of untreated rats and human lumbar CSF, respectively. Mean levels of IAA in brains of anesthetized rats, perfused free of blood, did not differ significantly from mean levels of anesthetized, nonperfused controls or from untreated rats. The source or sources of IAA in brain and CSF are unknown. Because IAA is a potent agonist at gamma-aminobutyrate receptors, it merits examination as a regulator in brain.

Disposition of ketoconazole, an oral antifungal, in humans.

The pharmacology of ketoconazole was studied in patients with fungal infections. After administration of 50-, 100-, and 200-mg doses of ketoconazole, there was a linear increase in the area under the curve of serum concentrations; this was not apparent when higher doses of ketoconazole were given. An increase in the area under the curve occurred in patients receiving 200 mg daily who were restudied after 1 to 12 months of therapy. However, normalized area under the curve appeared to decrease after higher doses were administered chronically. The half life ranged from 2.0 to 3.3 h. Peak serum concentrations up to 50 micrograms/ml were detected in this study, and potentially therapeutic concentrations were detectable up to 26 h after high doses. Ketoconazole penetrated the saliva and inflamed joint fluid and meninges, although variably, and could be demonstrated in some other tissue compartments. In the presence of renal failure, ketoconazole disposition was not altered, whereas in the presence of hepatic insufficiency, an alteration in disposition was suggested. The interactions of ketoconazole and other drugs were studied. Of note, antacids did not significantly affect ketoconazole pharmacokinetics (nor did meals), and ketoconazole and warfarin did not appear to affect the pharmacokinetics of the other.

Postoperative pharmacokinetics and sympatholytic effects of dexmedetomidine.

UNLABELLED: Dexmedetomidine is a selective alpha2-adrenoceptor agonist with centrally mediated sympatholytic, sedative, and analgesic effects. This study evaluated: 1) pharmacokinetics of dexmedetomidine in plasma and cerebrospinal fluid (CSF) in surgical patients; 2) precision of a computer-controlled infusion protocol (CCIP) for dexmedetomidine during the immediate postoperative period; and 3) dexmedetomidine's sympatholytic effects during that period. Dexmedetomidine was infused postoperatively by CCIP for 60 min to eight women, targeting a plasma concentration (Cp) of 600 pg/mL. Before, during, and after infusion, blood was sampled to determine plasma concentrations of norepinephrine, epinephrine, and dexmedetomidine, and CSF was sampled to determine dexmedetomidine concentrations (C[CSF]). Heart rate and arterial blood pressure were measured continuously from 5 min before until 3 h after the end of infusion. During the infusion, Cp values generally exceeded the target value: median percent error averaged 21% and ranged from -2% to 74%; median absolute percent error averaged 23% and ranged from 4% to 74%. After infusion, C(CSF) was 4% +/- 1% of Cp. Because C(CSF) barely exceeded the assay's limit of quantitation, CSF pharmacokinetics were not determined. During the infusion, norepinephrine decreased from 2.1 +/- 0.8 to 0.7 +/- 0.3 nmol/L; epinephrine decreased from 0.7 +/- 0.5 to 0.2 +/- 0.2 nmol/L; heart rate decreased from 76 +/- 15 to 64 +/- 11 bpm; and systolic blood pressure decreased from 158 +/- 23 to 140 +/- 23 mm Hg. We conclude that infusion of dexmedetomidine by CCIP using published pharmacokinetic parameters overshoots target dexmedetomidine concentrations during the early postoperative period. Hemodynamic and catecholamine results suggest that dexmedetomidine attenuates sympathetic activity during the immediate postoperative period. IMPLICATIONS: We studied the pharmacokinetic and sympatholytic effects of dexmedetomidine during the immediate postoperative period and found that during this period, the published pharmacokinetic data slightly overshoot target plasma dexmedetomidine concentrations. We also found that heart rate, blood pressure, and plasma catecholamine concentrations decrease during dexmedetomidine infusion.