Population pharmacokinetics and pharmacodynamics of imipenem in neutropenic adult patients.

OBJECTIVE: Imipenem is recommended in patients with chemotherapy-induced febrile neutropenia. Although alterations of antibiotic pharmacokinetic parameters have been reported in such patients, little data is available on imipenem. METHODS: Prospective, single-center, non-interventional pharmacokinetic cohort study in adults with chemotherapy-induced febrile neutropenia. Critically ill patients were excluded. Imipenem was administered as a 30-min infusion of 1000 mg/8h. Total imipenem plasma concentrations were assayed by high-performance liquid chromatography during neutropenia and just after neutrophil recovery. We estimated population pharmacokinetic parameters of imipenem by non-linear mixed-effect modelling using the SAEM algorithm. RESULTS: Sixteen patients were included in the study, including nine women (56.3%), median age 37 years (range, 18.3; 78.3). Eight patients had an hematological malignancy (50.0%) and seven had a solid tumor (43.8%). Imipenem pharmacokinetics were best described by a one-compartment model with first-order elimination. Mean values for imipenem were: clearance 14.3L/h and 10.9L/h and volume of distribution 20.7L and 14.5 L during neutropenia and after recovery, respectively. Imipenem plasma area under the curve at steady state was reduced by 23% during neutropenia. However, all patients achieved a pharmacodynamic target of %fT>MIC ≥ 40% with a regimen of 1000 mg/8 h or 500 mg/6 h, for MICs up to 2 mg/L. The pharmacodynamics profile for a target of %fT > MIC = 100% was however less favorable with 500 mg/6 h or 1000 mg/8 h either during or after neutropenia. CONCLUSION: Pharmacokinetic/pharmacodynamic goals for imipenem were similar in patients during and after neutropenia, despite reduced plasma exposure.

Assessment of the targeting specificity of a fluorescent albumin conceived as a preclinical agent of the liver function.

In the context of increasing liver diseases, no contrast agent is currently available in Europe and the United States to directly assess the liver function. Only neolactosylated human serum albumin is being clinically used in Asia. In order to perform preclinical studies in the context of liver diseases, we conceived a fluorescent lactosylated albumin for the quantification of liver functional cells (l-Cyal). Precise characterization was achieved in order to determine the amounts of lactose and Cyanine 5 (Cy5) coupled to the albumin. In addition, potential aggregation was characterized by asymmetrical flow field-flow fractionation hyphenated to multi-angle light scattering (AF4-MALS). The optimal functionalized albumin exhibited a mass greater than 87 kDa which corresponds to the addition of 34 lactose moieties per protein and 1-2 Cy5 labels. Also, no significant formation of aggregates could be identified due to the modification of the native albumin. In healthy mice, the accumulation of l-Cyal in the liver and its selectivity for hepatocyte cells were shown by optical imaging and flow cytometry. Administration of l-Cyal to mice bearing liver metastases showed a reduced signal in the liver related to a decrease in the number of hepatocytes. The l-Cyal bioimaging contrast agent could be particularly useful for assessing the state of liver related diseases.

Quantification of residual dimethylsulfoxide after washing cryopreserved stem cells and thawing tissue grafts.

Dimethylsulfoxide (DMSO) is a cryoprotective substance often used to allow long term storage of stem cells or tissue grafts. However, a high frequency of adverse events is associated with the infusion of thawed cells. These events are in part due to DMSO, leading many cell therapy facilities to introduce a washing step before the delivery of the grafts. The lack of method for evaluating the residual quantities of this substance in the reinfused cells led us to develop a technique, based on capillary zone electrophoresis for assaying DMSO. The cryoprotectant was measured in 55 hematopoietic stem cell grafts, 6 parathyroids and 5 blood vessels immediately after thawing and after washing or bathing in a saline solution. The results showed that DMSO reduction in stem cell grafts reached more than 90% after the washing procedure. Furthermore, this study has shown that 2 washing steps significantly improved DMSO elimination as compared to 1 washing step. For parathyroids and blood vessels, bathing the tissues after thawing in a saline solution allowed more than 95% DMSO reduction. This study demonstrated that the technique of DMSO measurement used here, is simple and feasible on complex matrices such as protein samples after dilution. It is an appropriate method for residual quantification of the cryoprotectant before graft.

Quantification of urinary allantoin by capillary zone electrophoresis during recombinant urate oxydase (rasburicase) therapy.

OBJECTIVES: Rasburicase (Fasturtec) is used to prevent or treat hyperuricemia associated with chemotherapy. We developed a capillary zone electrophoresis method to measure urinary allantoin, the degradation product of uric acid by rasburicase. DESIGN AND METHODS: Electrophoresis was performed using a P/ACE 5500 system (Beckman) with a fused silica capillary tube and a UV-visible detector set at 214 nm. Urine samples from 10 patients with non-Hodgkin's lymphoma were analyzed to validate the technique. RESULTS: Using a sodium tetraborate running buffer, urinary allantoin was separated from related compounds and internal standard in less than 30 min. The method was linear up to 1.25 g/L (quantification limit: 30 mg/L); precision was below 10%. The total amount of allantoin excreted in patients treated by rasburicase ranged from 1.5 g to 7.9 g/4 days. CONCLUSION: This CZE assay is a simple, rapid and reproducible method to measure allantoin in urine. Different elimination profiles have been found in patients treated with rasburicase.

Preclinical evaluation of an automated closed fluid management device: Cytomate, for washing out DMSO from hematopoietic stem cell grafts after thawing.

Infusion of dimethylsulfoxide (DMSO) contained in cryopreserved and thawed hematopoietic stem cell (HSC) grafts is frequently associated with mild or moderate adverse reactions, and occasionally with more severe events including neurological symptoms. The severity of these complications is related to the amount of residual DMSO. We evaluated a recently available, closed, automated and 'cgmp (current good manufacturing practice) compliant' device (CytoMate) for its ability to wash out DMSO at the expense of a limited loss of viable CD34(+) cells. A total of 16 procedures were carried out with 39 blood HSC bags intended for destruction. Mean amounts of DMSO for each cellular product (one, two or three bags) were between 12.2 and 39.6 g before thawing; after the washing procedure, residual DMSO quantities were between 0.1 and 3.7 g. When set up to reproducibly allow for a more than 96% elimination of DMSO, processing of thawed cells with the CytoMate cell processor resulted in a mean recovery of viable total cells, CD34(+) cells and lymphocyte subsets above 60%. We conclude that this simple and efficient washing technique is suitable for routine processing of HSC grafts. Clinical studies will demonstrate whether a reduction in the incidence of adverse effects associated with DMSO infusion is observed.

Simultaneous determination of total plasma glutathione, homocysteine, cysteinylglycine, and methionine by high-performance liquid chromatography with electrochemical detection.

We here describe an ion-exchange high-performance liquid chromatography technique with electrochemical detection for rapid quantification of glutathione, homocysteine, cysteinylglycine, and methionine. The analytical validation of the technique showed within-assay and between-assay coefficients of variation between 3.1 and 4.3%, and 3.7 and 8.6%, respectively. Percentages of recovery for overload and dilution tests were between 87 and 120%. Detection limits were 1 micromol/L for methionine and 0.5 micromol/L for other compounds. There was no interference with any physiological and pharmacological substances possessing a thiol function. Aminothiol concentrations determined in 100 control subjects (50 women and 50 men) showed no age- or sex-rated differences for except for homocysteine which was increased (+ 28%) in oldest subjects of both sexes. In 60 patients at risk (30 with chronic renal failure, 30 with diabetes), homocysteine concentration was significantly increased. No variation in other aminothiols was observed in diabetic subjects. Methionine was decreased and cysteinylglycine was increased in patients with chronic renal failure. The present technique-rapid, easy to use, and reliable-appears suitable for routine application in the exploration of aminothiol metabolic pathways including mechanisms of hyperhomocysteinemia.

Micellar electrokinetic capillary chromatography quantification of cytosine arabinoside and its metabolite, uracil arabinoside, in human serum.

Cytosine arabinoside (Ara-C) is widely used to induce remission in adult granulocytic leukemia. High doses can be infused in refractory leukemia or in relapse. After injection, Ara-C is quickly metabolized to uracil arabinoside (Ara-U), the main inactive metabolite. We here described a micellar electrokinetic capillary chromatography (MECC) method to simultaneously determine Ara-C/Ara-U in human serum using 6-O-methylguanine as an internal standard. The assay was linear from 6.25 to 200 microg/ml with a quantification limit between 3 and 6 microg/ml. The analytical precision was satisfactory between 2 and 4.3% (within-run) and 3.7 and 7.3% (between-runs). This assay was applied to the analysis of serum from acute granulocytic leukemia patient treated by high doses cytarabine (3 g/m2 body surface).

Comparison of urinary markers for bone resorption in multiple myeloma.

Multiple myeloma causes extensive bone remodeling. Classical biochemical markers such as urinary calcium have poor sensitivity for detecting multiple myeloma bone remodeling. New biochemicals have been developed including a carboxyterminal telopeptide of collagen I (CTX). We used an immunoenzymatic assay to determine urinary CTX in 60 patients with multiple myeloma. This marker was evaluated with regard to total pyridinolines, urinary calcium, radiological features, pain and response to treatment with bisphosphonates. In patients with bone involvement, CTX concentrations were significantly higher (+230%) than those of deoxypyridinoline (DPD) (+175%) and pyridinolines (PYD) (+130%). In all patients we have found a close correlation between CTX and DPD but not between CTX and PYD. Compared to radiological features, CTX was more sensitive (97%) and specific (96%) than DPD. After treatment by bisphosphonates, the fall in CTX concentrations was paralleled to urinary calcium and more marked than pyridinolines. Although our results need to be confirmed, CTX appears to be a potential marker to explore bone involvement in multiple myeloma.

Quantification of residual dimethyl sulfoxide in supernatants of haematopoietic stem cells by capillary zone electrophoresis.

Dimethyl sulfoxide (DMSO) is a chemical compound that is used to preserve haematopoietic stem cells during freezing at -180 degrees C. As DMSO is largely removed by washing before reinjection of cells into a patient, accidents (notably cardiovascular) are infrequent. The lack of a method for evaluating the residual quantities of this product led us to develop a technique for assaying DMSO by capillary zone electrophoresis without extraction. This simple, rapid and precise technique was applied to the supernatant of cell pellets of thirteen patients before and after washing.

Urinary carboxyterminal telopeptide of collagen I as a potential marker of bone metastases chemotherapy monitoring in breast cancer.

Breast cancers frequently have osteoclastic bone metastases that are difficult to monitor and treat. Bone scintigraphy with 99mTc-labeled biphosphonates is still the reference method for detecting and localizing bone involvement. Classical biochemical markers such as urinary calcium have poor sensitivity for detecting and monitoring metastases of breast cancers. New biochemical markers for the study of bone remodeling have recently been developed, including a degradation product of the C-terminal end of the telopeptide of type I collagen (CTX). We used an immunoenzymatic assay technique for urinary CTX in 84 pre- and post-menopausal women and demonstrated a correlation between scintigraphic scores and urinary CTX concentrations. CTX values are significantly different between the control group and patients with bone metastasis, except those with score 0. There is a regular increase in urinary CTX concentration from score 0 (no abnormal uptake) to score 4 (diffuse carcinomatosis). There is no significant variation between control population and score 0 to 3 for urinary calcium. Only women with scintigraphic score 4 have significantly increased urinary calcium concentrations. Measuring CTX in pre- and post-menopausal patients during breast cancer chemotherapy might be of great interest for monitoring the development of metastases and the therapeutic efficacy of chemotherapy.

4-methylpyrazole monitoring during haemodialysis of ethylene glycol intoxicated patients.

4-methylpyrazole (4-MP) was administered IV during haemodialysis of two ethylene glycol-intoxicated patients with anuric renal failure. The plasma 4-MP concentration decreased after each pass through the dialyser, indicating its dialysability in humans. In these two cases, the extraction coefficient was 0.78 and 0.71, and the mean dialysance was calculated to be 137 and 117 ml.min-1, corresponding to a 4-MP removal rate of 83 and 50 mg.h-1, respectively. The results imply that a higher rate of 4-MP infusion would be needed to replace 4-MP lost due to metabolism and to haemodialysis. The treatment of two ethylene glycol poisoned patients who were haemodialysed raised the problem of the dialysance of 4-MP. A recent study in pigs indicated that the amount of 4-MP removed by haemodialysis was significant [8]. No data were available for man. The aim of the study was to evaluate the dialysability of 4-MP in the two intoxicated patients, and to estimate how to compensate for 4-MP elimination during haemodialysis.

Effects of acute ethanol administration on the uptake of 59Fe-labeled transferrin by rat liver and cerebellum.

The uptake of iron by the liver and cerebellum was measured in rats using [59Fe]transferrin. An acute ethanol load (50 mmol/kg body wt., i.p.) elicited a significant increase in the hepatic and cerebellar non-heme iron concentration. The uptake of 59Fe by the liver and the cerebellum was significantly greater in the ethanol-treated rats than in control animals. The administration of allopurinol prior to the ethanol load prevented the changes in liver and cerebellar non-heme iron content. Moreover pretreatment with allopurinol reduced the ethanol-induced enhancement of 59Fe uptake by the liver and completely prevented the changes in 59Fe uptake by the cerebellum. These effects of allopurinol lead us to suggest that oxygen-derived free radicals are involved in the ethanol-induced disturbances of iron uptake both at the hepatic and cerebellar level.

Efficacy of 4-methylpyrazole in ethylene glycol poisoning: clinical and toxicokinetic aspects.

Potentially fatal ethylene glycol intoxication in an adult with normal renal function was treated with 4-methylpyrazole administered three hours after the incident occurred. The plasma ethylene glycol concentration was 3.5 g l-1 on admission. The metabolic acidosis present on admission resolved within four hours, and the subsequent clinical course was uneventful. The apparent plasma half-life of ethylene glycol was 16 h and the mean renal and plasma clearances of ethylene glycol were 24 and 25 ml min-1, respectively. These results support the hypothesis that complete blockade of hepatic metabolism of ethylene glycol is achieved by 4-methylpyrazole. The only side-effect observed as a result of treatment was a transient slight increase in serum transaminase activity.

Simultaneous determination of ethylene glycol, propylene glycol, 1,3-butylene glycol and 2,3-butylene glycol in human serum and urine by wide-bore column gas chromatography.

A method has been developed for the separation and measurement of ethylene glycol and three other glycols (propylene glycol, 1,3-butylene glycol and 2,3-butylene glycol) in biological samples by wide-bore column gas chromatography with a flame ionization detector. The method used 1,3-propylene glycol (1,3-propanediol) as an internal standard. The method was linear at least from 2 to 1000 micrograms/ml, with a detection limit of 1 microgram/ml. Analytical recoveries were 89-98% for the different concentrations. Precision studies showed coefficients of variation of 1.5-7.7% for the different concentrations. The assay was applied to the analysis of biological samples from two patients who had ingested ethylene glycol and/or other glycols in a suicide attempt.

Steady-state population pharmacokinetics of sustained release theophylline in adult asthmatic patients.

The steady-state population pharmacokinetics of theophylline were studied in 52 asthmatic adult patients who received sustained-release theophylline as armophylline or euphylline. A total of 92 steady-state plasma theophylline concentration-dosage pairs were analyzed using a nonlinear mixed effects model. The pharmacokinetic model used was a one-compartment open model with single path Michaelis-Menten elimination. Dosage was adjusted to body weight. The effects of age, gender, alcohol consumption, cigarette smoking, dosage form, concurrent treatment with beta-agonists or steroids, outpatient dosing, and plasma caffeine concentration on maximum elimination rate (Vm) and Michaelis constant for theophylline metabolism (Km) were investigated. Hypothesis testing produced a final model in which Km = 0.42 (mg/l), and Vm (mg/kg per day) was based on cigarette smoking and dosage form, with Vm = 7.54 + 2.01 (smoking) + 1.08 (euphylline). Estimated coefficients of variation for interindividual variability in Km and Vm were 162.6% and 48.1%, respectively. Residual variability in dosage rates was estimated as 0.90 mg/kg per day. The identification of factors influencing theophylline disposition should prove useful for the a priori design of theophylline dosage regimens and monitoring of drug levels during therapy.

Effect of allopurinol on the hepatic and cerebellar iron, selenium, zinc and copper status following acute ethanol administration to rats.

An acute ethanol load (50 mmol/kg, i.p.) induces an increase in the total non-heme iron and in the low-molecular-weight non-heme iron complexes (LMW-Fe) content both in liver and cerebellum. This increase in LMW-Fe is associated with a decrease in some essential trace elements (selenium, zinc, copper) playing a role in the anti-oxidant system. These changes could contribute to the enhancement in lipid peroxidation which occurs at the hepatic and cerebellar level following the ethanol administration. The administration of allopurinol prior to the ethanol load prevents the changes in non-heme iron and trace elements. This prevention may contribute to the protective effects of allopurinol on the ethanol-induced oxidative stress.

Effect of acute ethanol administration on the subcellular distribution of iron in rat liver and cerebellum.

An acute ethanol load (50 mmol/kg, i.p.) produced altogether a decrease in the non-heme iron content of the serum and an increase in the iron content in liver and cerebellum. Subcellular fractionation studies indicated that the non-heme iron accumulated by the liver, 4 hr after the ethanol load, was recovered in light mitochondria, microsomes and cytosol, and that iron accumulated by the cerebellum was localized in heavy mitochondria, light mitochondria, microsomes and cytosol. The low molecular weight chelatable (LMWC) iron content as well as the percentage of total non-heme iron represented by LMWC-iron were increased in the cytosol of liver and cerebellum after the ethanol load. These results suggest that an acute ethanol load induces (i) a shift in the distribution between circulating and tissular non-heme iron; (ii) an increase in the cytosolic LMWC-iron which, by favouring the biosynthesis of reactive free radicals, may contribute to lipid peroxidation in liver and cerebellum.

[Alcohol, iron and oxidative stress]. / Alcool, fer et stress oxydatif.

An oxidative stress has been reported to occur at the hepatic level after ethanol administration. We recently reported that such a stress is also apparent at the cerebellar level during acute ethanol intoxication in rats. Since low molecular weight iron chelates (LMW-Fe) are involved in the biosynthesis of aggressive prooxidant species we presently studied the influence of acute and chronic ethanol administration on hepatic and cerebellar total non-heme iron and LMW-Fe. The results show that an acute ethanol load (50 mmoles/kg b. wt.) administered (i.p.) to male Sprague-Dawley rats elicits altogether a decrease in the non-heme iron content of the serum and a highly significant increase in the hepatic and cerebellar non-heme iron concentration. The LMW-Fe content as well as the percentage of total non-heme iron represented by LMW-Fe are increased at the same time in the cytosolic fraction isolated from hepatic and cerebellar homogenates of the acutely ethanol-treated rats. The ethanol-induced disturbances in the non-heme iron content of liver and cerebellum can be prevented by the administration of allopurinol, which is known to reduce the severity of the oxidative stress observed in these tissues after an acute ethanol load. To study the effects of chronic ethanol administration, rats were given during 4 weeks a 10% (v/v) solution of ethanol in water as sole drinking fluid. The average daily ethanol consumption was 7-9 g. In such alcohol-fed rats the non-heme iron content was decreased by 31% in the serum whereas it was increased by 18% in the liver and by 30% in the cerebellum.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of variations of subcutaneously infused desferrioxamine and iron movements in thalassaemia children.

Desferrioxamine (DFO) plus ferrioxamine (FO) variations and alterations in plasma and urinary iron (Fe) levels were investigated in eight children with thalassaemia major during a 12-h s.c. DFO infusion at a dose of 40 mg/kg body weight. During the infusion, blood samples were regularly taken and total urine was also regularly collected in all patients. In the plasma, a mean DFO plus FO plateau level of 9 mg/l was reached after 4 h and remained steady in the subsequent 8 h. At 30 h the mean DFO plus FO concentration in plasma was still 4.5 mg/l. At 30 h, the urinary excretion ranged from 15% to 70% of the infused dose (mean: 42%). In plasma, the Fe concentration increased on average by 20% (range 10%-30%), remained steady during the DFO infusion, then returned to the basal level after 16-24 h. Urinary Fe excretion started early and still persisted 18 h after the infusion. The amount excreted at 30 h ranged from 5 to 27 mg (mean: 13.6 mg). This study emphasizes the delay in obtaining a DFO plus FO plateau in plasma, the important interindividual variations and the slow decrease of the drug after the end of the infusion. It points out the delay and the values of the urinary Fe excretion compared to the plasmatic and urinary drug variations.