Development of a simple and rapid method to determine the unbound fraction of dolutegravir, raltegravir and darunavir in human plasma using ultrafiltration and LC-MS/MS.

Dolutegravir, raltegravir and darunavir are three antiretroviral drugs widely used in combined antiretroviral therapies. These three drugs are highly bound to plasma proteins. Compared to the total concentration, the concentration of unbound drug which is considered as the only pharmacological active form should be more informative to improve therapeutic drug monitoring in patients to avoid virological failure or toxicity. The aim of the present study was to develop an ultrafiltration protocol and a LC-MS/MS method to simultaneously determine the concentrations of the unbound dolutegravir, raltegravir and darunavir in human plasma. Finally, 150 µL of plasma was ultrafiltrated using Centrifree® ultrafiltration devices with ultracel YM-T membrane (cutoff 30 KDa) during 5 min at 37 °C at 1500 g. Then, 20 µL of the ultrafiltrate were injected into the LC-MS/MS system. The chromatographic separation was carried out on a BEH C18 column using a mobile phase containing deionized water and acetonitrile, both with 0.05 % (v/v) of formic acid, with a gradient elution at a flow rate of 0.5 mL/min. The run time was only 4 min. The calibration curve ranged from 0.5-200 ng/mL for dolutegravir, 1 to 400 ng/mL for raltegravir and 10-4000 ng/mL for darunavir. This method was validated with a good precision (inter- and intra-day CV% lower than 14 %) and a good accuracy (inter- and intra-day bias between -5.6-8.8 %) for all the analytes. This method is simple, reliable and suitable for pharmacokinetic studies.

Dosing Recommendations for Lamotrigine in Children: Evaluation Based on Previous and New Population Pharmacokinetic Models.

Lamotrigine is a broad-spectrum antiepileptic drug with high interindividual variability in serum concentrations in children. The aims of this study were to evaluate the predictive performance of pediatric population pharmacokinetic (PPK) models published on lamotrigine, to build a new model with our monitoring data and to evaluate the current recommended doses. A validation cohort included patients treated with lamotrigine who had a serum level assayed during therapeutic drug monitoring (TDM). PPK models published in the literature were first applied to the validation cohort. We assessed their predictive performance using mean prediction errors, root mean squared errors, and visual predictive checks. A new model was then built using the data. Dose simulations were performed to evaluate the doses recommended. We included 270 lamotrigine concentrations ranging from 0.5 to 17.9 mg/L from 175 patients. The median (range) age and weight were 11.8 years (0.8-18 years) and 32.7 kg (8-110 kg). We tested 6 PPK models; most had acceptable bias and precision but underestimated the variability of the cohort. We built a 1-compartment model with first-order absorption and elimination, allometric scaling, and effects of inhibitor and inducer comedications. In our cohort, 22.6% of trough concentrations were below 2.5 mg/L. In conclusion, we proposed a PPK model that can be used for TDM of lamotrigine in children. In our population, a high percentage of children had low trough concentrations of lamotrigine. As the intervals of recommended doses are large, we suggest aiming at the higher range of doses to reach the target concentration.

HPLC-MS/MS method for the simultaneous quantification of dolutegravir, elvitegravir, rilpivirine, darunavir, ritonavir, raltegravir and raltegravir-ß-d-glucuronide in human plasma.

Therapeutic drug monitoring (TDM) is essential in the optimization of antiretroviral (ARV) treatments. In this work, we describe a new method for the simultaneous quantification of six molecules: the three novel ARV agents dolutegravir (DTG), elvitegravir (ELV) and rilpivirine (RPV), the first integrase inhibitor raltegravir (RAL) and its major metabolite the raltegravir-ß-d-glucuronide (RAL-GLU), an protease inhibitor darunavir (DRV) and its booster ritonavir (RTV) in human plasma. The drugs were extracted from 100 µL of plasma by a simple method of protein precipitation using acetonitrile. The separation was carried out on a Kinetex phehyl-hexyl column using a phase mobile composed of 55 % of water (0.05 % formic acid,v/v) and 45 % of methanol (0.05 % formic acid,v/v). The flow rate was set at 0.5 mL/min. The calibration ranged from 60 to 15000 ng/mL for DRV, from 20 to 5000 ng/mL for DTG and ELV, from 10 to 2500 ng/mL for RAL, RAL-GLU, RTV and RPV. The proposed method was validated with a good precision (inter- and intra-day CV% inferior to 12.3 %) and a good accuracy (inter- and intra-day bias between -9.9 % and 10 %) for all the analytes. The proposed method is simple, reliable and suitable for therapeutic drug monitoring (TDM) and for pharmacokinetics studies.

Simultaneous quantification of levofloxacin, pefloxacin, ciprofloxacin and moxifloxacin in microvolumes of human plasma using high-performance liquid chromatography with ultraviolet detection.

Levofloxacin, pefloxacin, ciprofloxacin and moxifloxacin are four fluoroquinolones used in the treatment of serious bacterial infections. The antibacterial activity of fluoroquinolones is concentration dependent. Therefore, therapeutic drug monitoring in daily clinical practice is warranted to ensure the therapy's efficacy and prevent bacterial resistance. The purpose of the present study was to develop a method using high-pressure liquid chromatography with an ultraviolet detector for simultaneous quantification of these four fluoroquinolones in human plasma. A 50 µL aliquot of plasma was precipitated by 200 µL of methanol using gatifloxacin as internal standard. The chromatographic separation was performed on a Kinetex XB-C18 column using a mobile phase composed of a mixture of orthophosphoric acid 0.4% (v/v), acetonitrile and methanol at a flow rate of 1.2 mL/min. Dual UV wavelength mode was used, with levofloxacin and moxifloxacin monitored at 293 nm, and pefloxacin and ciprofloxacin monitored at 280 nm. The calibration was linear over the ranges of 0.125-25 mg/L for levofloxacin, 0.1-20mg/L for moxifloxacin and 0.05-10 mg/L for both pefloxacin and ciprofloxacin. Inter- and intra-day trueness and precision were <13% for all the compounds under study. The proposed method was simple, reliable, cost-effective and suitable for therapeutic drug monitoring or pharmacokinetics studies.

Simulations of Valproate Doses Based on an External Evaluation of Pediatric Population Pharmacokinetic Models.

Valproate is an old-generation antiepileptic drug often used in children. The pharmacokinetics of valproate are noteworthy for a large and difficult to predict interindividual variability in measured serum concentrations and for saturable protein binding. A model-based approach to personalize valproate treatment could be relevant in pediatric patients. The aims of this study were to review all published valproate population pharmacokinetic models in children and assess them by external validation to determine their predictive performance. Through simulations with the best model, we evaluated dosing regimen. A validation data set included valproate serum concentrations assayed during routine therapeutic drug monitoring of epileptic children. We applied to our population 11 published pediatric population pharmacokinetic models. For each model, predictive performance was assessed by external validation, using bias and precision calculations as well as goodness-of-fit plots. Dose simulations were conducted with the best predictive model to evaluate dosing regimen. The validation data set contained 178 valproate concentrations ranging from 13.4 to 128 mg/L from 114 patients. The best model exhibited a mean prediction error of 6.6 mg/L and a root mean squared error of 25.1 mg/L, with no model misspecification evidenced by visual predictive check. In our cohort, half the patients had a trough concentration <50 mg/L. Simulations suggested increasing doses, especially for children ≤40 kg. External evaluation of published valproate pharmacokinetic models enabled us to identify a suitable model for simulations and Bayesian forecasting. Dosing regimen should be adjusted to weight, with decreasing doses with increasing weight.

Population Pharmacokinetic Model to Optimize Cefotaxime Dosing Regimen in Critically Ill Children.

BACKGROUND: During sepsis, optimal plasma antibiotic concentrations are mandatory. Modifications of pharmacokinetic parameters could lead to low drug concentrations and therefore, insufficient therapeutic levels. OBJECTIVE: The aim of this study was to build a population pharmacokinetic model for cefotaxime and its metabolite desacetylcefotaxime in order to optimize individual dosing regimens for critically ill children. METHODS: All children aged < 18 years, weighing more than 2.5 kg, and receiving intermittent cefotaxime infusions were included in this study. Cefotaxime and desacetylcefotaxime were quantified by high-performance liquid chromatography. Pharmacokinetics were described using the non-linear mixed-effect modeling software MONOLIX, and Monte Carlo simulations were used to optimize dosing regimen in order to maintain serum concentrations above the target concentration (defined at 2 mg·L-1) throughout the dosing interval. RESULTS: We included 49 children with a median (range) postnatal age of 23.7 (0.2-229) months, and median body weight (range) of 10.9 (2.5-68) kg. A one-compartment model with first-order elimination adequately described the data. Median (range) values for cefotaxime clearance, desacetylcefotaxime clearance, and volume of distribution were 0.97 (0.3-7.1) L·h-1, 3.2 (0.6-16.3) L·h-1, and 0.3 (0.2-0.41) L·kg-1, respectively. Body weight and postnatal age were statistically significant covariates. Cefotaxime-calculated residual concentrations were low, and no patient succeeded in attaining the target. Unlike intermittent administration, a dosing regimen of 100 mg·kg-1·day-1 administered by continuous infusion provided a probability of target attainment of 100%, regardless of age and weight. CONCLUSIONS: Standard intermittent cefotaxime dosing regimens in critically ill children are not adequate to reach the target. We showed that, for the same daily dose, continuous infusion was the only administration that enabled the target to be attained, for children over 1 month of age. As continuous administration is achievable in the pediatric intensive care unit, it should be considered for clinical practice. TRIAL REGISTRATION NUMBER: Registered at http://www.clinicaltrials.gov , NCT02539407.

Evaluation of oxaliplatin exposure of healthcare workers during heated intraperitoneal perioperative chemotherapy (HIPEC).

The aim of this study was to evaluate air and surface contaminations, and internal contamination of healthcare workers during open-abdomen HIPEC using oxaliplatin. Platinum (Pt) was measured in urine of exposed workers and in multiple air and surface samples. Three successive HIPEC procedures were investigated in each of the two hospitals participating in the study. Analysis of air samples did not detect any oxaliplatin contamination. Heavy contamination of the operating table, the floor at the surgeon's feet, and the surgeon's overshoes were observed. Hand contamination was observed in surgeons using double gloves for intra-abdominal chemotherapy administration, but not in those using three sets of gloves. Pt was not detected in urine samples obtained after HIPEC (<5 ng/L). The main risk of HIPEC is related to direct or indirect skin exposure and can be prevented by correct use of adapted protective equipment.