Overcoming stability challenges during continuous intravenous administration of high-dose amoxicillin using portable elastomeric pumps.

While treatment of serious infectious diseases may require high-dose amoxicillin, continuous infusion may be limited by lack of knowledge regarding the chemical stability of the drug. Therefore, we have performed a comprehensive study so as to determine the chemical stability of high-dose amoxicillin solutions conducive to safe and effective continuous intravenous administration using portable elastomeric pumps. First, amoxicillin solubility in water was assessed within the range of 25 to 300 mg/mL. Then, amoxicillin solutions were prepared at different concentrations (25, 50, 125, 250 mg/mL) and stored in different conditions (5±2°C, 25±1°C, 30±1°C and 37±1°C) to investigate the influence of concentration and temperature on the chemical stability of amoxicillin. Finally, its stability was assessed under optimized conditions using a fully validated HPLC-UV stability-indicating method. Degradation products of amoxicillin were investigated by accurate mass determination using high-resolution mass spectrometry. Amoxicillin displayed limited water solubility requiring reconstitution at concentrations below or equal to 150 mg/mL. Amoxicillin degradation were time, temperature as well as concentration-dependent, resulting in short-term stability, in particular at high concentrations. Four degradation products of amoxicillin have been identified. Among them, amoxicilloic acid and diketopiperazine amoxicillin are at risk of allergic reaction and may accumulate in the patient. Optimized conditions allowing for continuous infusion of high-dose amoxicillin has been determined: amoxicillin should be reconstituted at 25 mg/mL and stored up to 12 hours at room temperature (22 ± 4°C) or up to 24 hours between 4 and 8°C.

Validation of a probe for assessing deconjugation of glucuronide and sulfate phase II metabolites assayed through LC-MS/MS in biological matrices.

LC-MS/MS has been proposed in various areas such as Therapeutic Drug Monitoring (TDM), Human Biomonitoring (HBM), disease diagnosis, clinical toxicology and doping control to identify and quantify chemical parents and their metabolites in biological matrices. To determine the total content of a xenobiotic (unconjugated+conjugated forms), an enzymatic hydrolysis step is required. Most studies in the literature have not controlled the effectiveness of the deconjugation process because no method has been described for that purpose. Therefore the aim of this study was to develop and validate a deconjugation probe using a LC-MS/MS method. In order to estimate deconjugation using ß-glucuronidase and/or sulfatase, 4-methyl-umbelliferone (MU) and its conjugates were used as markers. Glucuronidase/sulfatase was added to plasma or urine spiked with 4-methylumbelliferyl-ß-d-glucuronide (MUG) and 4-methylumbelliferyl sulfate (MUS) and umbelliferone, which was used as the internal standard. After incubation at 37°C during 90min, MU appears as a result of the deconjugation of MUG and MUS. The concentrations of the 3 markers were determined using LC-MS/MS. Trueness and precision of the LC-MS/MS method were determined by quality control analysis at three different levels of concentration covering the whole range of calibration. In both matrices, the analytical method allows quantification of the different compounds, with good linearity, trueness and precision and negligible matrix effects. The method was applied with success to deconjugation assay using active glucuronidase/sulfatase in plasma and urine. The probe developed in this study allows to ensure that enzymatic preparation is working properly in the frame of a quality system.

Determination of bisphenol A in water and the medical devices used in hemodialysis treatment.

Bisphenol A (BPA) is an endocrine disruptor found in food containers and plastic beverages and also in medical devices such as dialyzers. The aim of this study is while taking into account the BPA originating in medical devices and the water used in dialysate production, to provide the first published investigation of overall potential exposure to BPA during hemodialysis treatment in patients suffering from end-stage renal disease. BPA concentration in water (at each step of purification treatment) and in dialysate and BPA leaching from dialyzers were determined using solid-phase extraction coupled to ultra-high-performance-liquid chromatography tandem mass spectrometry. We have corroborated the hypothesis that a significant amount of BPA may migrate from dialyzers and also demonstrated that BPA is provided by the water used in dialysate production (8.0±5.2ngL(-1) on average) and by dialysis machine and dialysate cartridges, leading to dialysate contamination of 22.7±15.6ngL(-1) on average. Taking into account all the sources of BPA contamination that may come into play during a hemodialysis session, the highest exposure could reach an estimated 140ng/kg b.w./day for hemodialyzed patients, directly available for systemic exposure. Finally, BPA contamination should be taken into account as concerns both the medical devices commonly used in hemodialysis and purified water production systems.

Ultrasensitive determination of bisphenol A and its chlorinated derivatives in urine using a high-throughput UPLC-MS/MS method.

Bisphenol A (BPA) is a well-known endocrine disruptor. Chlorinated derivatives of BPA (ClxBPA) may be formed by reaction of chlorine with BPA present in drinking water. ClxBPA exhibit a higher level of estrogenic activity than BPA. While many studies have reported detectable BPA concentrations in urine, only very few studies were conducted in regards to ClxBPA. Since ClxBPA are potentially more toxic, it is important to assess large-scale exposure of the general population. Indeed, in the field of environment health, large studies are required to assess exposure to pollutants at ultratrace concentrations; therefore, analytical methods have to be rapid and sensitive. This work intends to validate a highly sensitive and rapid analytical method suitable to evaluate BPA and ClxBPA exposures during large-scale biomonitoring studies. For that purpose, a method based on online solid-phase extraction coupled with isotope dilution ultrahigh - performance liquid chromatography-tandem mass spectrometry was developed and validated according to accepted guidelines. The matrix-matched calibration curve ranged from 0.25 to 16.0 ng mL(-1) and from 0.025 to 1.60 ng mL(-1) for BPA and ClxBPA, respectively. This method was precise (the intra- and inter-day coefficients of variation of quality control were <16.4%) and accurate (bias ranged from -4.0 to 16.8%). The limit of quantification was validated at 0.25 and 0.025 ng mL(-1), for BPA and ClxBPA, respectively. The limit of detection was estimated for each experiment performed. Finally, this method is rapid and sensitive enough to be carried out during biomonitoring studies of BPA and ClxBPA in human urine.

Estimating drinking-water ingestion and dermal contact with water in a French population of pregnant women: the EDDS cohort study.

The aim of the present study, a part of the Endocrine Disruptor Deux-Sèvres (EDDS) cohort study, was to estimate water-use habits of pregnant French women. The study population consisted of 132 pregnant women living in Deux-Sèvres (France) in 2012-2013, in areas where drinking water is exclusively produced by surface water. Drinking-water data included ingested water (tap, bottled and filtered) and ingestion place (home, work and elsewhere). Dermal contact with water included showering, bathing, swimming, spa use, hand-washing and other water activities. Data were collected through face-to-face interviews at second and third trimesters of pregnancy with a 1-day-recall questionnaire. Intertrimestral differences in water-use habits were assessed. Predictors of water ingestion and duration of dermal contact with water were assessed with multiple linear regressions. At the second trimester of pregnancy, the mean total drinking-water ingestion was 1.8±0.6 l per day (mean and SD), 71% of which was tap water. Total drinking-water ingestion was not different between both trimesters but ingestion place differed. Dermal contact with water estimate was 188±118 and 173±92 min/week at second and third trimesters, respectively. Smoking increased water ingestion 777 ml/day 95% CI (171-1384). Duration of dermal contact in spring was 30 min/week 95% CI (13-48) higher than in winter. Obese women spend 26 min/week 95% CI (2-50) more showering than women with recommended weight. Our estimates of pregnant French women's exposure to water will help researchers to better assess water pollutant risks.

Semimechanistic pharmacokinetic-pharmacodynamic model with adaptation development for time-kill experiments of ciprofloxacin against Pseudomonas aeruginosa.

The objective of this study was to implement a semimechanistic pharmacokinetic-pharmacodynamic (PK-PD) model to describe the effects of ciprofloxacin against Pseudomonas aeruginosa in vitro. Time-kill curves were generated with an initial inoculum close to 5 x 10(6)CFU/ml of P. aeruginosa PAO1 and constant ciprofloxacin concentrations between 0.12 and 4.0 microg/ml (corresponding to 0.5x and 16x MIC). To support the model, phenotypic experiments were conducted with the PAO7H mutant strain, which overexpresses the MexEF OprN efflux pump and phenyl arginine beta-naphthylamide (PAbetaN), a known efflux inhibitor of main Mex multidrug efflux systems. A population approach was used for parameter estimation. At subinhibitory ciprofloxacin concentrations (0.12 and 0.25 microg/ml), an initial CFU decay followed by regrowth was observed, attesting to rapid emergence of bacteria with increased but moderate resistance (8-fold increase of MIC). This phenomenon was mainly due to an overexpression of the Mex protein efflux pumps, as shown by a 16-fold diminution of the MIC in the presence of PAbetaN in these strains with low-level resistance. A PK-PD model with adaptation development was successfully used to describe these data. However, additional experiments are required to validate the robustness of this model after longer exposure periods and multiple dosing regimens, as well as in vivo.