Methoxpropamine (MXPr) in powder, urine and hair samples: Analytical characterization and metabolite identification of a new threat.

Methoxpropamine (MXPr) is an arylcyclohexylamine dissociative drug with structural similarities with 3-MeO-PCE, ketamine and deschloroketamine. MXPr was identified for the first time in Europe in October 2019 in Denmark and is considered a new psychoactive substance. We undertook the molecular identification and characterization of MXPr in urine, hair and powder samples. We used a combination of several analytical methods: liquid-state nuclear magnetic resonance (NMR), infra-red spectroscopy (IR) and liquid chromatography high-resolution mass spectrometry (LC-HRMS). The second objective was to explore the metabolism of MXPr in silico and in vitro. To detect characteristic metabolites that prove MXPr consumption by urine analysis, pooled human liver microsome (pHLM) assays were performed and evaluated using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS). A software algorithm (Unifi®) was used to predict in silico biotransformations of MXPr. Three metabolites were identified in the in vitro studies including N-despropyl(nor)MXPr, O-desmethyl MXPr and dihydroMXPr. Most of these phase II metabolites were confirmed to be present in urine and hair samples collected from an MXPr consumer. This is the first report of the identification of MXPr in France with analytical findings. This study highlights the challenge of identifying new psychoactive substances (NPS) when they are missing from compound libraries and if a standard is not available. The use of various complementary analytical methods combined with HRMS offers a promising approach for the molecular characterization of NPS.

Determination of moxifloxacin in growth media by high-performance liquid chromatography.

A direct injection high-performance liquid chromatographic method with column switching has been developed to determine moxifloxacin in Mueller-Hinton broth. A LiChrocart 4-4 pre-column filled with a LiChrospher 100 RP 18, 5 microm and a 150 x 4.6 mm I.D. column packed with a Supelcozil ABZ+ Plus were used and led to a retention time of 5.70 min. Fluorescence detection allowed one to reach a quantification limit of 0.05 microg/ml with a 100-microl sample size. The standard curves were linear from 0.05 to 3.2 microg/ml. Intra- and inter-day imprecisions within the linearity range were < or =4.76 and < or =5.75%, respectively. The mean relative errors for the same day and the day-to-day inaccuracies ranged from -2.93 to +4.50% and from -1.10 to +6.00%, respectively. The method was demonstrated to be useful for pharmacokinetic-pharmacodynamic studies of moxifloxacin in an in vitro model.

Pharmacokinetic population study to describe cefepime lung concentrations.

Pharmacokinetic parameters of cefepime in 2 g plasma and lung tissue bid over 3 days to achieve the steady-state was studied in 16 patients (15 male, one female) subjected to lung surgery for bronchial epithelioma. The aims of this study were firstly to quantify cefepime lung diffusion with cefepime lung concentrations in comparison with cefepime serum concentrations, and secondly to estimate population pharmacokinetic parameters of cefepime in lung tissue using NONMEM. The mean characteristics of patients were: age, 60 years (range, 51-69 years), weight, 73 kg (range, 62-87 kg) and creatinine clearance, 77 ml/min (range, 62-92 ml/min). Both serum sample (two per patient) and lung sample (one per patient) cefepime concentrations were analysed by HPLC with UV detection. Five groups were made according to the time of sampling after the last cefepime intravenous infusion at the fifth infusion: 0.5 h (n=2), 2 h (n=5), 4 h (n=3), 8 h (n=3) and 12 h (n=3). The cefepime concentration ratio between lung and serum was calculated for each group and statistical analysis show no significant difference between groups. The mean concentration ratio between lung and serum was 101% (range, 70-130%). To explain this observation a two-compartment pharmacokinetic model with a population approach was used to describe pharmacokinetic parameters of cefepime both in lung and in serum. Serum was assimilated at the central compartment and lung was the peripheral compartment. NONMEM was used to estimate the mean and the variance of the pharmacokinetic parameters. Central volume of distribution (V(d)), steady-state volume of distribution (V(ss)), central clearance (CL) and transfer constants (K(cp)) from serum to lung and (K(pc)) from lung to serum were estimated. Central elimination half-life t(1/2Kbeta)was extrapolated from elimination constant beta. Results were: V(d)= 15.62 +/- 2.56 l, V(ss)= 17.58 +/- 2.58 l, CL = 3.65 +/- 1.25 l/h, beta = 0.234 h(-1), t(1/2beta)= 2.96 hours, K(cp)= 12.25 +/- 8.56 h(-1)and K(pc)= 0.242 +/- 0.085 h(-1). The results show that cefepime diffusion in lung occurs quickly without lagtime and in similar concentrations to that in serum.

New approach for accurate simulation of human pharmacokinetics in an in vitro pharmacodynamic model: application to ciprofloxacin.

An in vitro pharmacodynamic model using a disposable dialyser unit and computer-controlled devices was developed. Feedback control of peristaltic pump flow rates is used to maintain constant flow rates, thus avoiding the problem of the modification of the physical properties of the tubing that generally occurs. Fast equilibrium is obtained with capillaries, which allows simulation of the same kinetic profile in the central and the peripheral compartments. Thus, more accurate simulation of plasma, extracapillary fluid or whole tissue kinetics can be performed. Our model was validated by simulation of a 30 min infusion of a 200 mg dose, and of an oral administration of a 500 mg dose of ciprofloxacin.

Determination of moxifloxacin (BAY 12-8039) in plasma and lung tissue by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method with a new polymeric cartridge.

The aim of this study was to develop a high-performance liquid chromatographic (HPLC) assay for the determination of moxifloxacin in human plasma and lung tissue. The assay was based on HPLC with a Supelcosil ABZ+ column and ultraviolet detection set at a wavelength of 296 nm. The extraction procedure was characterized by a fully automated liquid-solid extraction using an OASIS column for the solid phase. The assay has been found to be linear and validated over the concentration range 3.2 to 0.025 microg/ml for moxifloxacin in plasma and from 16 to 0.25 microg/g for moxifloxacin in lung tissue. In future, the assay will support the pharmacokinetic study of the penetration of moxifloxacin in human lung tissue.

Determination of cefepime and cefpirome in human serum by high-performance liquid chromatography using an ultrafiltration for antibiotics serum extraction.

The aim of this study was to describe a high-performance liquid chromatography (HPLC) assay for the determination of cefepime and cefpirome in human serum without changing chromatographic conditions. The assay consisted to measure cefepime and cefpirome which were unbound to proteins having a molecular mass of 10,000 or more by ultrafiltration followed by HPLC with a Supelcosil ABZ+ column and UV detection at a wavelength of 263 nm. The assay was been found to be linear and has been validated over the concentration range 200 to 0.50 microg/ml for both cefepime and cefpirome, from 200 microl serum, extracted. In future, the assay will support therapeutic drug monitoring for cefepime and cefpirome in neutropenic patients in correlation with microbiological parameters such as MIC90 (minimal inhibitory concentration of antibiotic which kills 90% of the initial bacterial inoculum) and clinical efficacy.

Pharmacokinetics of isepamicin during continuous venovenous hemodiafiltration.

The objective of this study was to analyze the pharmacokinetics of isepamicin during continuous venovenous hemodiafiltration. Six patients received 15 mg of isepamicin per kg of body weight. The mean isepamicin concentration peak in serum was 62.88 +/- 18.20 mg/liter 0.5 h after the infusion. The elimination half-life was 7. 91 +/- 0.83 h. The mean total body clearance was 1.75 +/- 0.28 liters/h, and dialysate outlet (DO) clearance was 2.76 +/- 0.59 liters/h. The mean volume of distribution was 19.83 +/- 2.95 liters. The elimination half-life, DO clearance, and volume of distribution were almost constant. In this group of patients, the initial dosage of 15 mg/kg appeared to be adequate, but the dosage interval should be determined by monitoring residual isepamicin concentrations in plasma.

Determination of phosphonoformate (foscarnet) in calf and human serum by automated solid-phase extraction and high-performance liquid chromatography with amperometric detection.

An isocratic high-performance liquid chromatographic method with automated solid-phase extraction has been developed to determine foscarnet in calf and human serums. Extraction was performed with an anion exchanger, SAX, from which the analyte was eluted with a 50 mM potassium pyrophosphate buffer, pH 8.4. The mobile phase consisted of methanol-40 mM disodium hydrogenphosphate, pH 7.6 containing 0.25 mM tetrahexylammonium hydrogensulphate (25:75, v/v). The analyte was separated on a polyether ether ketone (PEEK) column 150x4.6 mm I.D. packed with Kromasil 100 C18, 5 microm. Amperometric detection allowed a quantification limit of 15 microM. The assay was linear from 15 to 240 microM. The recovery of foscarnet from calf serum ranged from 60.65+/-1.89% for 15 microM to 67.45+/-1.24% for 200 microM. The coefficient of variation was < or = 3.73% for intra-assay precision and < or =7.24% for inter-assay precision for calf serum concentrations ranged from 15 to 800 microM. For the same samples, the deviation from the nominal value ranged from -8.97% to +5.40% for same day accuracy and from -4.50% to +2.77% for day-to-day accuracy. Selectivity was satisfactory towards potential co-medications. Replacement of human serum by calf serum for calibration standards and quality control samples was validated. Automation brought more protection against biohazards and increase in productivity for routine monitoring and pharmacokinetic studies.

Fully automated high-performance liquid chromatography of ciprofloxacin with direct injection of plasma and Mueller-Hinton broth for pharmacokinetic/pharmacodynamic studies.

An isocratic high-performance liquid chromatographic method with column switching and direct injection has been developed to determine ciprofloxacin in plasma and Mueller-Hinton broth. An on-line dilution of the sample was performed with a loading mobile phase consisting of 173 mM phosphoric acid. The analyte was retained on a LiChrocart 4-4 precolumn filled with a LiChrospher 100 RP18, 5 microm. An electric-actuated system with two six-port valves allowed a clean-up step with a mixture 20 mM phosphate buffer (pH 3.5)-methanol (97:3, v/v) and the transfer of the analyte by a back-flush mode to a 150 x 4.6 mm I.D. column packed with a Kromasil C8 5 microm, using a mobile phase of 20 mM phosphate buffer (pH 3.5)-acetonitrile (85:15, v/v). Fluorescence detection allowed a quantification limit of 0.078 microg/ml with a 40-microl sample size. The method was evaluated to determine its usefulness in studying the pharmacokinetic/pharmacodynamic behaviour of ciprofloxacin in an in vitro model.

Simultaneous determination of ritonavir and saquinavir, two human immunodeficiency virus protease inhibitors, in human serum by high-performance liquid chromatography.

The aim of this study was to describe an high-performance liquid chromatographic assay for the simultaneous determination of two HIV protease inhibitors, saquinavir and ritonavir, in human serum. The method involved extraction of ritonavir and saquinavir from serum with the aid of solid-phase extraction C18 cartridges followed by high-performance liquid chromatography with a C8 column and ultraviolet detection set at a wavelength of 240 nm. The assay was linear and has been validated over the concentrations range of 0.5-32 microg/ml for ritonavir and 0.075-4.8 microg/ml for saquinavir, from 600 microl serum extracted. In future, the assay will be used to support human population pharmacokinetic studies, and therapeutic drug monitoring for ritonavir and saquinavir.

[Transplacental passage of epirubicin]. / Passage transplacentaire de l'épirubicine.

We studied the transplacental transfer of epirubicin, an anthracycline used for the treatment of different neoplastic disorders, in particular breast cancers, by in vitro perfusion of term human placenta. Placenta from women with uncomplicated pregnancy were collected immediately after vaginal delivery and put into 37 degrees C thermostated hood. Perfusion of foetal surface of the placenta by modified Earle's solution was started immediately after catheterisation at a flow rate of 6 ml/min and then so was the perfusion of the intervillous space at the rate of 12 ml/min. Samples were collected at different times after the initiation of the perfusion from arterial inflow and venous outflow respective of the maternal and foetal compartment. The transplacental transfer of epirubicin was investigated for two doses: 5 and 9 micrograms/ml. The mean transfer value of epirubicin is low (3.66 +/- 1.07%) for the two tested doses and is only slightly higher than doxorubicin transfer, which drug has provided rare accidents in the clinical reports. These results are in favour of a low placental toxicity of epirubicin. Clinical data have to be collected from pregnant women to confirm the low foetal toxicity of epirubicin.

Sensitive high-performance liquid chromatographic method for the determination of labetalol diastereoisomers in plasma samples without derivatization.

A direct high-performance liquid chromatographic assay for the determination of labetalol diastereoisomers in plasma without derivatization was developed. Baseline resolution of diastereoisomers was accomplished on a C18 bonded reversed-phase polymeric column with a basic (pH 11.5) mobile phase and isocratic elution. Sample treatment was optimized in order to achieve a complete extraction of labetalol diastereoisomers and to avoid racemization during extraction. Fluorimetric detection improved the selectivity and afforded a detection limit of 3 ng/ml for each diastereoisomer. This method is suitable for routine quantification of labetalol diastereoisomers and has been applied to a pharmacokinetic study in small laboratory animals.