Roselyne Boulieu

Determination of acyclovir in human plasma by high-performance liquid chromatography

A selective and sensitive isocratic high-performance liquid chromatographic method for the analysis of acyclovir in human plasma was described. Acid deproteinisation was used as sample treatment. Mean analytical recoveries were higher than 94% at low and high concentrations. The quantification limit was 0.1 mg/l for a plasma volume of 500 microl and precision study exhibits coefficients of variation lower than 5%. The method is suitable for therapeutic monitoring of acyclovir concentrations in organ-transplant recipients.

Protein binding of ketamine and its active metabolites to human serum

Abstract. Ketamine is an anaesthetic agent extensively used in intensive care patients, and it has proved its efficacy in the management of burned patients. In these patients, alterations in serum protein binding occur that may have significant clinical implications. Scarce data were observed in the literature about the binding of ketamine to human plasma proteins, and no data about the binding of its active metabolites, norketamine (NK) and dehydronorketamine (DHNK) were found. In this study, protein binding of ketamine, NK and DHNK in human serum were determined using the ultrafiltration technique. The percentage of drug bound to serum proteins at 30°C was found to be 69%, 60% and 50% for DHNK, ketamine and NK, respectively, while these percentages were 75%, 64% and 54% for DHNK, ketamine and NK respectively at 20°C. The binding of ketamine and its metabolites was independent of drug concentration.

High-performance liquid chromatographic determination of thiopurine metabolites of azathioprine in biological fluids

A selective and sensitive reversed-phase liquid chromatographic method for the analysis of thiopurine bases, nucleosides and nucleotides in biological samples was developed. A simple and rapid sample treatment procedure using perchloric acid deproteinization with dithiothreitol for the analysis of thiopurine bases and nucleosides is presented. The addition of dithiothreitol during sample collection and treatment improves recoveries. This procedure also allows the determination of thiopurine nucleotides by hydrolysis to their free bases after heating of the perchloric acid extract. The method was applied to the analysis of thiopurine metabolites in plasma and erythrocytes from lung-transplant patients under azathioprine therapy.

Effects of mutations on herpes simplex virus 1 thymidine kinase functionality: An in vitro assay based on detection of monophosphate forms of acyclovir and thymidine using HPLC/DAD

Discrimination between the mutations responsible for drug resistance and those of UL23 TK gene polymorphism can be difficult. A non-isotopic method has been developed to assess TK functionality by measuring monophosphate forms of both acyclovir (ACV) and thymidine using HPLC/DAD. Phenotypes of TKs could thus be characterized as TK altered (P84L, A189V, L227F), TK deficient (G200S, L291P) or TK partial (R163H). A reliable link between HSV UL23 TK mutations and ACV resistance is necessary for developing a powerful genotyping tool to detect ACV resistance quickly in clinical samples.

Ex-Vivo percutaneous absorption of enrofloxacin: Comparison of LMOG organogel vs. pentravan cream.

The objective of this study was to investigate the percutaneous absorption of enrofloxacin from two base formulations, Pentravan cream and LMOG organogel. Ex-vivo experiments were carried out on pig ear skin. The percutaneous permeation through pig skin of two formulations containing 5 wt% of enrofloxacin was measured and compared using Franz diffusion cells. At appropriate intervals up to 120 h, diffusion samples were taken and analyzed using HPLC assays. Permeation profiles were established and the parameters Tlag and flux values were calculated. In this ex-vivo study, the flux values were 0.35 μgcm(-2)h(-1) for Pentravan and 1.22 μgcm(-2)h(-1) for LMOG organogel, corresponding respectively to 7.9 % and 29.3 % of enrofloxacin absorbed after 120 h by these formulations. The lag time (T lag) of Pentravan and organogel were 6.32 and 0.015 h respectively. The absorption time to reach the antibiotic concentration of enrofloxacin (2 μgmL(-1)) in the receptor was 60 h with Pentravan and 30 h with the organogel, suggesting more effective treatment by the latter. Enrofloxacin contained in organogel could be absorbed through pig ear skin 3.7 times greater than that in Pentravan (commercial formulation). This study demonstrates the perspective of organogel formulations as potential drug delivery systems.

Cyclosporine monitoring in renal transplant recipients with induction therapy: C2 levels in patients monitored on C0

The aim of this retrospective study was to compare the cyclosporine C2 blood levels in renal transplant recipients with induction therapy, monitored on C0 levels during the early and long‐term post‐transplantation periods in different French transplantation centres, to the target values recommended by the International Consensus on Neoral® and used in the Mo2art study. A retrospective study was conducted by the therapeutic drug monitoring (TDM) committee of the French Pharmacological Society. Cyclosporine C0 and C2 concentrations from 168 renal transplant recipients were collected at different post‐transplantation periods by six TDM laboratories of transplantation centres from April 2001 to April 2002. Cyclosporine blood levels were determined by fluorescence polarization immunoassay (mFPIA, AxSYM, Abbott) or enzyme immunoassay (EMIT, Dade Behring). Most patients had C0 values in the recommended target ranges, with C2 levels below the targets used in the Mo2art study or proposed by the International Consensus Conference, both during the early and long‐term post‐transplantation periods. Sixty‐eight per cent of patients had C2 below 1500 μg/L ± 20% in the first 2 months post‐transplantation and 55% had C2 below 800 μg/L ± 20% in the late post‐transplantation period (>1 year). Cyclosporine dose should be increased by 40% on average during the first week post‐transplantation period and by 50% during the maintenance period to achieve the C2 targets. In France, most renal transplant recipients receiving induction agents monitored on C0 had C2 levels below the targets recommended by the International Consensus Conference. In clinical practice, the optimal therapeutic windows for CsA monitoring based on C2 needs to be more precisely defined, both during the early and long‐term post‐transplantation periods in renal transplant recipients receiving induction agents.

Pharmacokinetic-Pharmacodynamic Modelling of Ketamine in Six Neurotraumatised Intensive Care Patients

1 Universite Claude Bernard Lyon 1, Faculte de Pharmacie, Departement de Pharmacie Clinique de Pharmacocinetique et d’Evaluation du Medicament, Lyon, France 2 Hopital Neuro-Cardiologique, Laboratoire de Pharmacocinetique Clinique, Lyon, France 3 Hopital Neuro-Cardiologique, Service de Soins Intensifs Post-operatoires, Lyon, France 4 Universite de Montpellier I, Faculte de Pharmacie, Laboratoire de Pharmacocinetique Clinique, Montpellier, France

Detection of Enrofloxacin After Single-Dose Percutaneous Administration in Python regius, Boa constrictor imperator, and Acrantophis dumerili

Abstract In this study, the blood concentrations of enrofloxacin administered transdermally to 3 different reptilian species, Python regius, Acrantophis dumerili, and Boa constrictor imperator, at 50 mg/kg was determined. The formulation used was a transdermal commercial vehicle, Pentravan cream, a hydrophilic base emulsion that uses the liposomal technique to penetrate the skin. The enrofloxacin was incorporated at 5 wt% in the Pentravan cream, and the plasma concentrations of enrofloxacin and its metabolite ciprofloxacin were measured using high‐performance liquid chromatography. The results showed that the detected amounts of enrofloxacin and ciprofloxacin (0.33 and <0.15 &mgr;g/mL, respectively) were below the limit of quantification. Enrofloxacin was detected in P. regius and B. constrictor, while ciprofloxacin was detected only in A. dumerili. Although the values were unquantifiable, this study confirms the absorption of enrofloxacin. Therefore, these findings suggests that enrofloxacin may be a candidate for treatment using the transdermal route in certain reptile species.

Abnormal Purine and Pyrimidine Metabolism in Inherited Superactivity of PRPP Synthetase

Superactivity of phosphoribosylpyrophosphate synthetase (PRPPS), the enzyme catalyzing synthesis of the purine regulatory substrate, phosphoribosylpyrophosphate, (PRPP) from adenosine triphosphate (ATP) and ribose 5-phosphate, is an inherited disorder in which excessive enzyme activity is associated with uric acid overproduction and gout1. Erythrocytes and cultured fibroblasts from affected individuals show increases in PRPP concentration. The metabolic basis for the increase enzyme activity of PRPPS has been fully studied2-4 whereas data on alteration in nucleotide and nucleoside profiles are scare5. In this study the biochemical abnormalities in a patient with PRPPS superactivity was investigated.