[Guidelines for medical prescription of medical laboratory tests]. / Recommandations concernant la prescription d'examens de biologie médicale.

The implementation of a computer-assisted prescription is interesting for the laboratory to achieve requirements of NF EN ISO 15189 standard. The test redundancies are also studied and guidelines, founded on validated studies, are proposed. Some solutions concerning the management of orally-formulated prescriptions are given. Finally, a model of collaboration contract between the medical laboratory and the clinical unit is proposed.

[Guidelines for the order process of medical laboratory tests]. / Outils pour l'élaboration et la gestion des formulaires de demande d'examens de biologie médicale.

This document presents the requirements enumerated in the ISO 15189 standard to make reliable the formulation of a medical laboratory test order. The contents and the filling conditions of the request laboratory tests form are described, to clarify the interest of the information required. The purpose is to help to construct a specific formulation allowing the adequate realization of the laboratory tests but also to collect the needed clinical information essential to allow a relevant interpretation of the results with a goal of improvement of patient care. We present also the main forms required for special laboratory tests, particularly concerning the human genome. Finally, the criteria to be reviewed at the entry of the laboratory (contract review) during the request acceptation before its registration are enumerated.

[Guidelines relative to the collection and handling management of biological samples]. / Recommandations pour la maîtrise de l'étape de prélèvement des échantillons biologiques.

Guidelines relative to the management of samples collection and handling for common tests are proposed with a list of websites to improve knowledge concerning the practices of biological sampling. Then, methodology is given for the creation of an electronic primary sample collection manual for medical laboratory tests. A list containing the medical laboratory tests for which the information and/or particular documents are needed either for the request or interpretation is presented. Another list for some specific laboratory tests with special individual requirements is proposed. We give also items allowing a standardized description of laboratory tests to help to create a personalized list of the available examinations, facilitating the information of professionals.

6-tioguanine monitoring in steroid-dependent patients with inflammatory bowel diseases receiving azathioprine.

BACKGROUND: 6-Thioguanine (6-tioguanine) nucleotides are the active metabolites of azathioprine. AIM: The aim of the study was to evaluate the rate of clinical remission without steroids in steroid-dependent Crohn's disease and ulcerative colitis patients receiving azathioprine, the medium- and long-term efficacy and the predictive factors of clinical response when monitoring 6-tioguanine. METHODS: Steroid-dependent Crohn's disease and ulcerative colitis patients receiving either azathioprine or not (treated later with a daily dose of 2.5 mg/kg) were prospectively included. 6-tioguanine was monitored at 1 and 2 months and every 3 months thereafter for 1 year. The azathioprine dose was adapted to reach a 6-tioguanine level of >250 pmol/8 x 10(8) red blood cells. Thiopurine methyltransferase genotype/phenotype was evaluated in some patients. RESULTS: A total of 106 patients were prospectively included (70 Crohn's disease, 36 ulcerative colitis). The clinical remission rate without steroids in patients receiving azathioprine, in intention-to-treat analysis, was 72% and 59% at 6 and 12 months, respectively. The remission rate was significantly higher in patients with 6-tioguanine >250 pmol/8 x 10(8) RBC (86% and 69% at 6 and 12 months, respectively; P < 0.01). No significant difference was observed between Crohn's disease and ulcerative colitis patients whether treated by azathioprine or not on inclusion. In the univariate analysis, the absence of Crohn's disease stenosis, a 6-tioguanine level >250 pmol/8 x 10(8) RBC, and an increase of erythrocyte mean corpuscular volume were the factors predictive of a favourable clinical response. In the multivariate analysis, only a 6-tioguanine level of >250 pmol/8 x 10(8) red blood cells was a predictive factor of favourable clinical remission. CONCLUSIONS: Clinical remission without steroids is significantly more likely when monitoring 6-tioguanine so as to reach a level of >250 pmol/8 x 10(8) red blood cells in steroid-dependent Crohn's disease and ulcerative colitis patients receiving azathioprine (86% and 69% at 6 and 12 months, respectively).

Drug interaction between infliximab and azathioprine in patients with Crohn's disease.

BACKGROUND: A drug interaction has been observed between infliximab and methotrexate in rheumatoid arthritis. AIM: To look for an interaction between infliximab and azathioprine in Crohn's disease patients using the active metabolites of azathioprine: 6-tioguanine nucleotides. METHODS: Patients receiving azathioprine who required infliximab for ileo-colonic or ano-perineal Crohn's disease were recruited prospectively. 6-tioguanine nucleotide levels were evaluated before infusion, within 1-3 weeks after the first infusion and 3 months after the first infusion. The clinical outcome was evaluated by the Harvey-Bradshaw index or the closure of ano-perineal fistulas. RESULTS: Thirty-two patients were included (17 received one infusion and 15 received three infusions). The mean 6-tioguanine nucleotide level was comparable before and 3 months after the first infusion, but a significant increase was observed within 1-3 weeks after the first infusion (P < 0.001). In parallel, a significant decrease in leucocyte count and increase in mean corpuscular volume were observed; these modifications were normalized 3 months after infusion. An increase in 6-tioguanine nucleotide level of greater than 400 pmol/8 x 108 erythrocytes was strongly related to good tolerance and a favourable response to infliximab, with a predictive value of 100%. CONCLUSIONS: This prospective study provides evidence for a drug interaction between azathioprine and infliximab.

Pharmacokinetics of intrarectal nalbuphine in children undergoing general anaesthesia.

The pharmacokinetics of nalbuphine (0.3 mg/kg) administered by the rectal route were studied in ten children undergoing general anaesthesia for minor surgery. Blood sampling was carried out for 8 h after rectal administration and plasma drug concentrations were measured by high performance liquid chromatography using electrochemical detection after an optimized solid-phase extraction procedure. The mean time to achieve the maximum plasma concentration (Cmax = 24 +/- 15 ng/mL) was 25 +/- 11 min and the elimination half-life was 2.7 +/- 0.7 h. The coefficients of variation for Cmax and the concentration-time curve (AUC) were 62 and 68%, respectively. Although rectal absorption is considered irregular, the large intersubject variability is also explainable by a variable hepatic bypass for a drug, like nalbuphine, that undergoes extensive first-pass metabolism. No problem of analgesic efficacy or of local tolerance was reported. In conclusion, the rectal route of administration provides a rapid and reliable absorption of nalbuphine.

[Hematotoxicity caused by azathioprine genetically determined and aggravated by xanthine oxidase deficiency in a patient following renal transplantation]. / Hématotoxicité de l'azathioprine à déterminisme génétique aggravée par un déficit en xanthine oxydase chez une transplantée rénale.

Azathioprine is an immunosuppressor used with ciclosporin and corticosteroids after organ transplantation. Azathioprine is rapidly transformed into 6-mercaptopurine which in turn is metabolized by three competitive pathways: a) intracellular hypoxanthine guanine phosphoribosyl transferase leads to 6-thioguanine nucleotides which can damage chromosome DNA; b) thiopurine methyltransferase produces inactive methylated derivatives; c) xanthine oxidase produces thiouric acid. Due to inter-individual variations in the later two pathways, azathioprine dose must be adapted to each patient. A 48-year-old female patient underwent renal transplantation in 1994 and was given immunosuppressive therapy combining thymoglobulins, azathioprine and ciclosporin. Severe leukopenia (< 3000/mm3) occurred on day 5 requiring withdrawal of azathioprine. Known hypouricaemia (< 50 mumol/l) suggested xanthine oxidase deficiency. Laboratory results confirmed xanthine oxidase deficiency and also revealed reduced thiopurine methyltransferase activity (14.9 pmol/h/mg Hb). Azathioprine toxicity was confirmed by regression of the leukopenia after withdrawal and recurrence at rechallenge. Xanthine oxidase deficiency occurs in 2% of the general population. Reduced thiopurine methyltransferase activity affects 11% of the population. The combined presence of these two genetic anomalies led to early and sudden intolerance to azathioprine and emphasize the need to develop new immunosuppressor agents degraded by other metabolic pathways.

Rapid and sensitive high-performance liquid chromatographic assay for nalbuphine in plasma.

A simple and reliable reversed-phase high-performance liquid chromatographic method with adequate internal analog standardization and coulometric detection is described for the quantification of nalbuphine in plasma samples. The lower limit of detection was estimated to be 0.1 ng/ml. For routine analysis, the limit of quantification was set at 0.5 ng/ml and only a small plasma volume (500 microliters) was required. The nalbuphine calibration curve was linear over the concentration range 0-100 ng/ml. The recoveries of nalbuphine and 6-monoacetylmorphine, used as internal standard, were close to 85%. Due to the small sample volume of blood required, this highly sensitive, accurate and specific method is suitable for pharmacokinetic studies of nalbuphine, and particularly for drug monitoring in neonates born from mothers treated with nalbuphine.

Pharmacokinetics of apomorphine in parkinsonian patients.

Apomorphine, a dopamine agonist, has been used efficiently in parkinsonian patients to treat severe levodopa-induced on-off phenomenon. Motor improvement has been obtained both with continuous subcutaneous (SC) infusions, and multiple SC injections. So as to assist in the understanding of the clinical results, we studied the peripheral pharmacokinetics of apomorphine in 20 patients after intravenous (IV) or SC injections in the anterior abdominal wall and in the thigh at various doses, or SC infusion. Plasma apomorphine levels were measured by high-performance liquid chromatography with electrochemical detection. After an SC injection in the abdominal wall, the Tmax was brief (16 +/- 11 min) the drug was rapidly cleared from the plasma and had a short plasma half-life (69.7 +/- 25.8 min). The AUC was similar following SC and IV injections, suggesting that apomorphine was completely absorbed from subcutaneous tissue. Inter-subject variability in drug absorption was large. We noticed a trend towards a more complete absorption following injection in the abdominal wall rather than in the thigh. In patients chronically treated by continuous SC infusion, the apparent plasma half-life was five times longer than that following SC or IV injections. These pharmacokinetic data may explain the rapid onset and brief duration of clinical effects, and the usefulness of individual titration for intermittent SC apomorphine injections, and the smoother motor response obtained with continuous SC infusions.

[Pharmacokinetics of methohexital given by constant rate intravenous infusion]. / Pharmacocinétique du méthohexital administré en perfusion intraveineuse à débit constant.

The pharmacokinetic characteristics of a constant rate methohexitone infusion were studied in young ASA 1 patients undergoing maxillofacial surgery. They were randomly assigned to two groups; group M patients (n = 7) were given 9 mg.kg-1.h-1 of methohexitone for one hour, and group MF patients (n = 7) 9 mg.kg-1.h-1 of methohexitone with 7 micrograms.kg-1.h-1 of fentanyl, also for one hour. Blood samples for determining methohexitone concentrations were obtained at various times, from before the start of the methohexitone infusion up to 19 h afterwards. In twelve patients, a two-compartment model was appropriate to characterize the decrease of methohexitone concentration; for the other two (one in each group), a three-compartment model was applied. There were no statistically significant differences between the two groups. Elimination half-life in group M was 3.22 +/- 1.96 h, and total plasma clearance 8.54 +/- 2.8 ml.kg-1.min-1. The wide variations in pharmacokinetic parameters between subjects may explain some unpredictable variations in duration of action of methohexitone. Fentanyl did not modify methohexitone pharmacokinetics, which remained of the first order. However, it potentiated the barbiturate's action: extubation was only possible after stopping the infusion for 39.4 min +/- 22 min in group MF, and 15.4 min +/- 6 min in group M (p less than 0.01). At that time, plasma concentrations were respectively 3.12 +/- 0.99 mg.l-1 (group MF) and 5.71 +/- 2.09 mg.l-1 (group M), (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between plasma concentration and clinical efficacy after sublingual single dose apomorphine in Parkinson's disease.

Five patients with Parkinson's disease were given a single sublingual dose of apomorphine in 3 mg tablets (2 patients received 18 mg and 3 patients took 39 mg). The therapeutic effect appeared within 33.0 min and lasted 137 min. There was a significant correlation between peak concentration, area under the curve, dose (mg/kg) and the duration of the therapeutic effect.

Determination of 6-mercaptopurine and its metabolites in plasma or serum by high performance liquid chromatography.

A sensitive and accurate reversed phase liquid chromatographic assay was developed for the determination of 6-mercaptopurine (6MP) (the active metabolite of azathioprine) in human plasma. The assay involved extraction into acetonitrile and dichloromethane from plasma pretreated with 0.038 M of dithiothreitol solution. The residue was analyzed by isocratic chromatography on a C18 analytical column with UV detection at 326 nm. The average extraction recovery of 6MP was 85%. The method has been applied successfully to the determination of 6MP and its metabolites in pharmacokinetic studies.

CSF drug levels for children with acute lymphoblastic leukemia treated by 5 g/m2 methotrexate. A study from the EORTC Children's Leukemia Cooperative Group.

A multicenter EORTC study was conducted in children with acute lymphocytic leukemia to determine whether 5 g/m2 of methotrexate (MTX) (24 h i.v. infusion, four cycles) is an appropriate dosage for obtaining CSF drug concentrations approaching the critical cytotoxic level of 10(-6) M. A total of 193 cycles were analyzed for 58 patients. At the end of the 24 h infusion, the mean MTX serum level was 65.27 +/- 33.11 microM; the mean CSF MTX level was 1.47 +/- 1.1 microM; no significant difference in CSF MTX levels was observed between patients with (n = 20) and those without i.v. Ara-C (n = 38). The mean CSF MTX/serum MTX ratio was 0.029 +/- 0.027. CSF drug concentrations greater than or equal to 10(-6) M were achieved in 81% of the courses. The highest level was 8.4 X 10(-6) M. Only 5% of patients failed to achieve this drug concentration in at least one cycle. No significant correlation was observed between blood and CSF MTX levels. Mean CSF MTX levels were comparable from one cycle to another.

Bayesian estimation of cyclosporine clearance in bone marrow graft.

The dosage regimen of cyclosporine (CsA) can be individualized in patients by means of a test dose (TD) method in the few days before bone marrow graft. To simplify the test dosing protocol, we used a Bayesian estimation (BE) of CsA clearance requiring population data and partial kinetic information for a given patient. In the first part, 42 patients, aged 11-47 years, were given a 2-h infusion of CsA (4 mg.kg-1). CsA concentrations were determined in several blood samples. The obtained concentration-time curves were fitted according to a three-compartment model. Maximum likelihood estimation (MLE) allowed CsA determination of pharmacokinetic parameters. Early population parameters of CsA were determined using 22 TD by a two-stage method. In the remaining 20 patients, individual pharmacokinetic parameters were also computed by BE procedure, taking into account the above determined population parameters and CsA concentration determinations from three blood samples drawn at 5 and 30 min and 3 h after the end of TD infusion. In the second part, 16 patients were used to evaluate performance of BE in directly predicting target concentration values. Finally, early population characteristics were updated on the basis of 42 patients. Statistical comparisons between MLE and BE estimates of CsA clearance and between concentrations predicted after BE and those experimentally obtained showed that three blood CsA determinations allowed accurate clearance estimation and target concentration predictions. The method presented here can be used to calculate an individual CsA dosage regimen in real time, thus improving patient comfort.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetic of cyclosporin A]. / Pharmacocinétique de la ciclosporine A.

Pharmacokinetic studies of 13 children treated with cyclosporine A (CyA) were retrospectively analysed (9 renal transplants, 1 combined liver-kidney transplant, 1 heart transplant; 2 were treated for a nephrotic syndrome). The patients were separated into 2 groups: patients 0-15 years (group 1), patients 15-18 years (group 2). In comparison with adults (group 3), children of the 2 groups required higher CyA doses, related either to body weight or to body surface area. CyA dosage was performed by high performance liquid chromatography on whole blood samples. Despite higher doses, trough CyA levels were lower in groups 1 and 2 compared with group 3. Nephrotoxicity occurred in the only 2 children treated with CyA doses higher than 10 mg/kg/d.