Optimization of vigabatrin dosage in children with epileptic spasms: A population pharmacokinetic approach.

AIMS: Vigabatrin is an antiepileptic drug used to treat some forms of severe epilepsy in children. The main adverse effect is ocular toxicity, which is related to the cumulative dose. The aim of the study is to identify an acceptable exposure range, both through the development of a population pharmacokinetic model of vigabatrin in children enabling us to calculate patient exposure and through the study of therapeutic response. METHODS: We performed a retrospective study including children with epilepsy followed at Necker-Enfants Malades hospital who had a vigabatrin assay between January 2019 and January 2022. The population pharmacokinetic study was performed on Monolix2021 using a nonlinear mixed-effects modelling approach. Children treated for epileptic spasms were classified into responder and nonresponder groups according to whether the spasms resolved, in order to identify an effective plasma exposure range. RESULTS: We included 79 patients and analysed 159 samples. The median age was 4.2 years (range 0.3-18). A 2-compartment model with allometry and creatinine clearance on clearance best fit our data. Exposure analysis was performed on 61 patients with epileptic spasms. Of the 22 patients who responded (36%), 95% had an AUC0-24 between 264 and 549 mg.h.L-1. CONCLUSIONS: The population pharmacokinetic model allowed us to identify bodyweight and creatinine clearance as the 2 main factors explaining the observed interindividual variability of vigabatrin. An acceptable exposure range was defined in this study. A target concentration intervention approach using this pharmacokinetic model could be used to avoid overexposure in responder patients.

Systemic complement activation influences outcomes after allogeneic hematopoietic cell transplantation: A prospective French multicenter trial.

Complement activation has shown a role in murine models of graft-versus-host disease (GVHD) and in endothelial complications after allogeneic hematopoietic cell transplantation (allo-HSCT). However, its impact on post-transplant outcomes has not been so far fully elucidated. Here, we conducted a prospective multicentric trial (NCT01520623) performing serial measurements of complement proteins, regulators, and CH50 activity for 12 weeks after allo-HSCT in 85 patients receiving a myeloablative conditioning (MAC) regimen for various hematological malignancies. Twenty-six out of 85 patients showed an "activated" complement profile through the classical/lectin pathway, defined as a post-transplant decline of C3/C4 and CH50 activity. Time-dependent Cox regression models demonstrated that complement activation within the first weeks after allo-HSCT was associated with increased non-relapse mortality (hazard ratio [HR]: 3.69, 95% confident interval [CI]: 1.55-8.78, p = .003) and poorer overall survival (HR: 2.72, 95% CI: 1.37-5.39, p = .004) due to increased incidence of grade II-IV acute GVHD and in particular gastrointestinal (GI) GVHD (HR: 36.8, 95% CI: 12.4-109.1, p < .001), higher incidences of thrombotic microangiopathy (HR: 8.58, 95% CI: 2.16-34.08, p = .0022), capillary leak syndrome (HR: 7.36, 95% CI: 2.51-21.66, p = .00028), post-engraftment bacterial infections (HR: 2.37, 95% CI: 1.22-4.63, p = .0108), and EBV reactivation (HR: 3.33, 95% CI: 1.31-8.45, p = .0112). Through specific immune staining, we showed the correlation of deposition of C1q, C3d, C4d, and of C5b9 components on endothelial cells in GI GVHD lesions with the histological grade of GVHD. Altogether these findings define the epidemiology and the clinical impact of complement classical/lectin pathway activation after MAC regimens and provide a rational for the use of complement inhibitory therapeutics in a post-allo-HSCT setting.

Alternative routes for tranexamic acid treatment in obstetric bleeding (WOMAN-PharmacoTXA trial): a randomised trial and pharmacological study in caesarean section births.

OBJECTIVE: To examine the safety, efficacy and pharmacology of intravenous (IV), intramuscular (IM) and oral tranexamic acid (TXA) use in pregnant women. DESIGN: Randomised, open-label trial. SETTING: Hospitals in Pakistan and Zambia. POPULATION: Women giving birth by caesarean section. METHODS: Women were randomised to receive 1 g IV, 1 g IM, 4 g oral TXA or no TXA. Adverse events in women and neonates were recorded. TXA concentration in whole blood was measured and the concentrations over time were examined with population pharmacokinetics. The relationship between drug exposure and D-dimer was explored. The trial registration is NCT04274335. MAIN OUTCOME MEASURES: Concentration of TXA in maternal blood. RESULTS: Of the 120 women included in the randomised safety study, there were no serious maternal or neonatal adverse events. TXA concentrations in 755 maternal blood and 87 cord blood samples were described by a two-compartment model with one effect compartment linked by rate transfer constants. Maximum maternal concentrations were 46.9, 21.6 and 18.1 mg/L for IV, IM and oral administration, respectively, and 9.5, 7.9 and 9.1 mg/L in the neonates. The TXA response was modelled as an inhibitory effect on the D-dimer production rate. The half-maximal inhibitory concentration (IC50 ) was 7.5 mg/L and was achieved after 2.6, 6.4 and 47 minutes with IV, IM and oral administration of TXA, respectively. CONCLUSIONS: Both IM and oral TXA are well tolerated. Oral TXA took about 1 hour to reach minimum therapeutic concentrations and would not be suitable for emergency treatment. Intramuscular TXA inhibits fibrinolysis within 10 minutes and may be a suitable alternative to IV.

Piperacillin Population Pharmacokinetics and Dosing Regimen Optimization in Critically Ill Children Receiving Continuous Renal Replacement Therapy.

We aimed to develop a piperacillin population pharmacokinetic (PK) model in critically ill children receiving continuous renal replacement therapy (CRRT) and to optimize dosing regimens. The piperacillin plasma concentration was quantified by high-performance liquid chromatography. Piperacillin PK was investigated using a nonlinear mixed-effect modeling approach. Monte Carlo simulations were performed to compute the optimal scheme of administration according to the target of 100% interdose interval time in which concentration is one to four times above the MIC (100% fT > 1 to 4× MIC). A total of 32 children with a median (interquartile range [IQR]) postnatal age of 2 years (0 to 11), body weight (BW) of 15 kg (6 to 38), and receiving CRRT were included. Concentration-time courses were best described by a one-compartment model with first-order elimination. BW and residual diuresis (Qu) explained some between-subject variabilities on volume of distribution (V), where [Formula: see text], and clearance (CL), where [Formula: see text], where CLpop and Vpop are 6.78 L/h and 55.0 L, respectively, normalized to a 70-kg subject and median residual diuresis of 0.06 mL/kg/h. Simulations with intermittent and continuous administrations for 4 typical patients with different rates of residual diuresis (0, 0.1, 0.25, and 0.5 mL/kg/h) showed that continuous infusions were appropriate to attain the PK target for patients with residual diuresis higher than 0.1 mL/kg/h according to BW and MIC, while for anuric patients, less frequent intermittent doses were mandatory to avoid accumulation. Optimal exposure to piperacillin in critically ill children on CRRT should be achieved by using continuous infusions with escalating doses for high-MIC bacteria, except for anuric patients who require less frequent intermittent doses.

Management and outcome of native joint septic arthritis: a nationwide survey in French rheumatology departments, 2016-2017.

OBJECTIVES: To describe current management and outcome of native joint septic arthritis (NJSA) in French rheumatology departments. METHODS: For this retrospective, nationwide multicentric study, 127 French rheumatology departments were contacted to report up to 12 cases of NJSA that occurred between 1 January 2016 and 31 December 2017. Characteristics, diagnosis procedures, therapeutic management and outcome were recorded. RESULTS: Overall, 362 patients were included (mean age 64.0±18.6 years, median Charlson comorbidity index 3.5 (0-14)). Knee was the most frequent site (n=160 (38.9%)), and Staphylococcus sp (n=185 (51.4%)), the most frequent pathogen. All patients received antibiotics for a mean duration of 46.8 (±22.0) days, including intravenous route for a mean of 17.2 (±15.4) days. Management was heterogeneous. Surgical procedure was performed in 171 (48.3%), joint immobilisation in 128 (43.8%). During follow-up, 91 (28.3%) patients have had serious complications and 28 (9.2%) of them died. Factors associated with 1-year mortality were age (OR 1.08, 95% CI 1.04 to 1.13; p<0.001), Charlson's index (OR 1.30, 95% CI 1.06 to 1.58; p=0.012), presence of bacteraemia (OR 4.02, 95% CI 1.35 to 11.99; p=0.008), antibiotic use in the previous 3 months (OR 3.32, 95% CI 1.11 to 9.87; p=0.029) and Staphylococcus aureus NJSA compared with Streptococcus sp. NJSA (OR 7.24, 95% CI 1.26 to 41.68, p=0.027). The complete recovery with no adverse joint outcome at 1 year was observed in n=125/278 patients (55.0%). CONCLUSION: Prognosis of NJSA remained severe with a high rate of morbimortality. Its management was very heterogeneous. This study highlights the importance of the new French recommendations, published after the completion of the study, in order to facilitate NJSA management.

Amiodarone/N-desethylamiodarone population pharmacokinetics in paediatric patients.

The population pharmacokinetics of amiodarone and its active metabolite, N-desethylamiodarone (DEA) were investigated in paediatric patients with arrhythmias, mainly supraventricular tachycardias. A total of 55 patients from the Department of Pediatric Intensive Care and Pediatric Cardiology at Necker-Enfants malades Hospital (Paris, France) provided 72 concentrations for both amiodarone and DEA following repeated oral or intravenous administration. Blood samples drawn for biological analyses were used for drug concentrations. Plasma amiodarone concentrations were measured by a liquid chromatography method coupled with mass spectrometry and the data were modelled using the software Monolix 2019R2. Parent pharmacokinetics was described with a 2-compartment open model and the metabolite formation was connected to the central parent compartment. Parameter estimates scaled allometrically on bodyweight (normalized to 70 kg) were, respectively (% relative standard errors, RSEs), 6.32 (31%) and 7.14 L/h (26%) for elimination (CL) and intercompartmental clearances and 167 (31%) and 3930 (32%) L for V1 and V2 . Oral bioavailability was 0.362 (21.5%). The clearance between subject variability (ω, square root of the variance) was 0.462 (RSE 21%). The proportional residual variabilities were respectively 0.453 (RSE 13%) and 0.423 (RSE 12%) for amiodarone and DEA respectively. The terminal half-lives were 34 and 14.5 days for amiodarone and DEA, respectively. A dosage schedule was established for 3 weight bands in 2 time periods. The high pharmacokinetic variability suggests that therapeutic drug monitoring might be useful to improve individual efficacy and safety.

General clinical and methodological considerations on the extrapolation of pharmacokinetics and optimization of study protocols for small molecules and monoclonal antibodies in children.

Pharmacometric modelling plays a key role in both the design and analysis of regulatory trials in paediatric drug development. Studies in adults provide a rich source of data to inform the paediatric investigation plans, including knowledge on drug pharmacokinetics (PK), safety and efficacy. In children, drug disposition differs widely from birth to adolescence but extrapolating adult to paediatric PK, safety and efficacy either with pharmacometric or physiologically based approaches can help design or in some cases reduce the need for clinical studies. Aspects to consider when extrapolating PK include the maturation of drug metabolizing enzyme expression, glomerular filtration, drug excretory systems, and the expression and activity of specific transporters in conjunction with other drug properties such as fraction unbound. Knowledge of these can be used to develop extrapolation tools such as allometric scaling plus maturation functions or physiologically based PK. PK/pharmacodynamic approaches and well-designed clinical trials in children are of key importance in paediatric drug development. In this white paper, state-of-the-art of current methods used for paediatric extrapolation will be discussed. This paper is part of a conect4children implementation of innovative methodologies including pharmacometric and physiologically based PK modelling in clinical trial design/paediatric drug development through dissemination of expertise and expert advice. The suggestions arising from this white paper should define a minimum set of standards in paediatric modelling and contribute to the regulatory science.

Pharmacokinetics of tranexamic acid after intravenous, intramuscular, and oral routes: a prospective, randomised, crossover trial in healthy volunteers.

BACKGROUND: In response to the World Health Organization call for research on alternative routes for tranexamic acid (TXA) administration in women with postpartum haemorrhage, we examined the pharmacokinetics of TXA after i.v., i.m., or oral administration. METHODS: We conducted a randomised, open-label, crossover trial in 15 healthy volunteers who received i.v. TXA 1 g, i.m. TXA 1 g, or oral TXA solution 2 g. Blood samples were drawn up to 24 h after administration. Tranexamic acid concentration was measured with liquid chromatography-mass spectrometry, and the parameters of the pharmacokinetic models were estimated using population pharmacokinetics. RESULTS: The median time to reach a concentration of 10 mg L-1 was 3.5 min for the i.m. route and 66 min for the oral route, although with the oral route the target concentration was reached in only 11 patients. Median peak concentrations were 57.5, 34.4, and 12.8 mg L-1 for i.v., i.m., and oral routes, respectively. A two-compartment open model with body weight as the main covariate best fitted the data. For a 70 kg volunteer, the population estimates were 10.1 L h-1 for elimination clearance, 15.6 L h-1 for intercompartmental clearance, 7.7 L for the volume of central compartment, and 10.8 L for the volume of the peripheral compartment. Intramuscular and oral bioavailabilities were 1.0 and 0.47, respectively, showing that i.m. absorption is fast and complete. Adverse events were mild and transient, mainly local reactions and low-intensity pain. CONCLUSIONS: The i.m. (but not oral) route appears to be an efficient alternative to i.v. tranexamic acid. Studies in pregnant women are needed to examine the impact of pregnancy on the pharmacokinetics. CLINICAL TRIAL REGISTRATION: EudraCT 2019-000285-38; NCT03777488.

Ciprofloxacin population pharmacokinetics during long-term treatment of osteoarticular infections.

BACKGROUND: Ciprofloxacin is an antibiotic used in osteoarticular infections owing to its very good bone penetration. Very few pharmacokinetic data are available in this population. OBJECTIVES: To investigate oral ciprofloxacin population pharmacokinetics in adult patients treated for osteoarticular infections and propose guidance for more effective dosing. METHODS: A retrospective population-pharmacokinetic analysis was performed on 92 consecutive hospitalized patients in the orthopaedic department. Ciprofloxacin plasma samples were obtained on one or two occasions during treatment. Plasma concentration was measured using ultra-performance liquid chromatography system coupled with tandem mass spectrometry. Data analysis was performed using a non-linear mixed-effect approach via Monolix 2019R2. RESULTS: A total of 397 plasma samples were obtained with 11.5% and 41.6% of patients being below the therapeutic target for Gram-negative and staphylococcal infections, respectively. Ciprofloxacin pharmacokinetics were best described by a two-compartment model with a first-order absorption. Ciprofloxacin apparent plasma clearances and volumes of distribution were dependent on patients' fat-free mass according to the allometric rule. Elimination clearance was also positively related to renal function through the modification of diet in renal disease equation (MDRD) and rifampicin co-administration. When patients are co-treated with rifampicin, ciprofloxacin dosage should be increased by 50% to 60%. CONCLUSIONS: This study showed that free-fat mass was a better size predictor than total body weight for ciprofloxacin clearance and volumes terms. Moreover, both MDRD and rifampicin status were significant predictors of individual ciprofloxacin clearance. Our study suggests that individual adjustment of ciprofloxacin dose in osteoarticular infections with less-susceptible bacteria might be indicated to reach required efficacy targets.

Estimation of piperacillin clearance with different glomerular filtration rate formulas in critically ill children.

AIMS: Glomerular filtration rate (GFR) is difficult to assess in critically ill children using gold standard method and alternatives are needed. This study aimed to determine the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children, using a published piperacillin pharmacokinetics (PK) population model. METHODS: All children hospitalized in the paediatric intensive care unit of a single institution who were receiving piperacillin were included. PK were described using the nonlinear mixed effect modelling software MONOLIX. In the initial PK model, GFR was estimated according to the Schwartz 1976 formula. We evaluated a set of 12 additional validated formulas, developed using plasma creatinine and/or cystatin C concentrations, in the building model to assess the lowest between-subject variability for piperacillin clearance. RESULTS: We included 20 children with a median (range) postnatal age of 1.9 (0.1-19) years, body weight of 12.5 (3.5-69) kg. Estimated GFR according to the Schwartz 1976 formula was 160.5 (38-315) mL min-1 1.73 m-2 . Piperacillin clearance was best predicted by the Bouvet combined formula. CONCLUSION: The combined Bouvet formula was the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children.

Population pharmacokinetics of ropivacaine used for local infiltration anaesthesia during primary total unilateral and simultaneous bilateral knee arthroplasty.

BACKGROUND: Ropivacaine is commonly used in local infiltration anaesthesia (LIA) as pain management after total knee arthroplasty (TKA). Although considered safe, no studies evaluated the pharmacokinetics of high-dose ropivacaine infiltration in simultaneous bilateral TKA. METHODS: We studied 13 patients undergoing unilateral and 15 undergoing bilateral TKA. Standard LIA technique was used with ropivacaine 0.2%, 200 ml (400 mg) injected peri-articularly in each knee. Free and total plasma concentrations of ropivacaine were measured within 24 h using liquid chromatography-mass spectrometry. A population pharmacokinetic model was built using non-linear mixed-effects models. RESULTS: Peak free ropivacaine concentration was 0.030 (0.017-0.071) µg ml-1 (mean [99% confidence interval]) vs 0.095 (0.047-0.208) µg ml-1, and peak total ropivacaine concentration was 0.756 (0.065-1.222) µg ml-1vs 1.695 (0.077-3.005) µg ml-1 for unilateral and bilateral TKA, respectively. The pharmacokinetics was ascribed a one-compartment model with first-order absorption. The main identified covariates were protein binding, allometrically scaled body weight on clearance and volume, and unilateral or bilateral surgery on volume. CONCLUSIONS: This is the first study to investigate the pharmacokinetics of free and total ropivacaine after unilateral and bilateral TKA. A population model was successfully built and peak free ropivacaine concentration stayed below previously proposed toxic thresholds in patients undergoing unilateral and bilateral TKA receiving LIA with high-dose ropivacaine. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04702282.

Pharmacokinetics of intramuscular tranexamic acid in bleeding trauma patients: a clinical trial.

BACKGROUND: Intravenous tranexamic acid (TXA) reduces bleeding deaths after injury and childbirth. It is most effective when given early. In many countries, pre-hospital care is provided by people who cannot give i.v. injections. We examined the pharmacokinetics of intramuscular TXA in bleeding trauma patients. METHODS: We conducted an open-label pharmacokinetic study in two UK hospitals. Thirty bleeding trauma patients received a loading dose of TXA 1 g i.v., as per guidelines. The second TXA dose was given as two 5 ml (0·5 g each) i.m. injections. We collected blood at intervals and monitored injection sites. We measured TXA concentrations using liquid chromatography coupled to mass spectrometry. We assessed the concentration time course using non-linear mixed-effect models with age, sex, ethnicity, body weight, type of injury, signs of shock, and glomerular filtration rate as possible covariates. RESULTS: Intramuscular TXA was well tolerated with only mild injection site reactions. A two-compartment open model with first-order absorption and elimination best described the data. For a 70-kg patient, aged 44 yr without signs of shock, the population estimates were 1.94 h-1 for i.m. absorption constant, 0.77 for i.m. bioavailability, 7.1 L h-1 for elimination clearance, 11.7 L h-1 for inter-compartmental clearance, 16.1 L volume of central compartment, and 9.4 L volume of the peripheral compartment. The time to reach therapeutic concentrations (5 or 10 mg L-1) after a single intramuscular TXA 1 g injection are 4 or 11 min, with the time above these concentrations being 10 or 5.6 h, respectively. CONCLUSIONS: In bleeding trauma patients, intramuscular TXA is well tolerated and rapidly absorbed. CLINICAL TRIAL REGISTRATION: 2019-000898-23 (EudraCT); NCT03875937 (ClinicalTrials.gov).

Forecasting the Patients Flow at Pediatric Emergency Departments.

Emergency departments (EDs) have a key role in the public health system. They are facing a constant growth of their volume. Forecasting the daily volume is a major tool to adapt the allocation of resources. In this paper, we focus on pediatric EDs. They are specific by their strong seasonal variation, determined by the academic pace. The main contribution of this paper is to integrate the effects of this pace to the annual seasonality. We also tried out to improve the daily forecasting by forecasting the week means of the flow first. We trained and tested these models specifically on the pediatric EDs of Paris university hospital trust. For the eight pediatric EDs gathered, on average for the years 2016 to 2019, we forecasted the daily volume with a Mean Absolute Percentage Error (MAPE) of 6.6% for a 7-days forecasting, 7.1% for a 14-days forecasting and 7.6% for a 28-days forecasting. Account of rhythm allows a performance increase, with results respectively 7%, 10.1% and 8.4% better relatively to a baseline model based on a periodic regression on the weeks.

Effect of Pregnancy on Unbound Raltegravir Concentrations in the ANRS 160 RalFe Trial.

A population pharmacokinetic model was developed to explore the pharmacokinetics modification of unbound raltegravir during pregnancy. The RalFe ANRS160 study was a nonrandomized, open-label, multicenter trial enrolling HIV-infected pregnant women receiving a combined antiretroviral regimen containing 400 mg raltegravir twice daily. Biological samples were collected during the third trimester of pregnancy (between 30 and 37 weeks of gestational age) and at postpartum (4 to 6 weeks after delivery). A population pharmacokinetic model was developed with Monolix software. A total of 360 plasma samples were collected from 43 women during pregnancy and postpartum. The unbound raltegravir was described by a one-compartment model with a transit compartment with first-order absorption, evolving to bound raltegravir (by a linear binding to albumin) or metabolism to RAL-glucuronide or to a first-order elimination, with a circadian rhythm. During pregnancy, the absorption was decreased and delayed and the raltegravir elimination clearance and glucuronidation increased by 37%. Median total and unbound area under the curve from 0 to 12 h significantly decreased by 36% and 27% during pregnancy. Median total trough concentration (Ctrough) decreased significantly in the evening (28%); however, the median total Ctrough in the morning, unbound Ctrough in the morning, and unbound Ctrough in the evening showed a nonsignificant decrease of 16%, 1%, and 15%, respectively, during pregnancy compared to the postpartum period. This is the first study reporting the pharmacokinetics of unbound raltegravir during pregnancy. As unbound Ctrough did not significantly decrease during the third trimester, the pregnancy effect on raltegravir unbound concentrations was not considered clinically relevant. (This study has been registered at ClinicalTrials.gov under identifier NCT02099474.).

Population pharmacokinetics of meropenem in critically ill children with different renal functions.

PURPOSE: We aimed to develop a meropenem population pharmacokinetic (PK) model in critically ill children and simulate dosing regimens in order to optimize patient exposure. METHODS: Meropenem plasma concentration was quantified by high-performance liquid chromatography. Meropenem PK was investigated using a non-linear mixed-effect modeling approach. RESULTS: Forty patients with an age of 16.8 (1.4-187.2) months, weight of 9.1 (3.8-59) kg, and estimated glomerular filtration rate (eGFR) of 151 (19-440) mL/min/1.73 m2 were included. Eleven patients received continuous replacement renal therapy (CRRT). Concentration-time courses were best described by a two-compartment model with first-order elimination. Body weight (BW), eGFR, and CRRT were covariates explaining the between-subject variabilities on central/peripheral volume of distribution (V1/V2), inter-compartment clearance (Q), and clearance (CL): V1i = V1pop × (BW/70)1, Qi = Qpop × (BW/70)0.75, V2i = V2pop × (BW/70)1, CLi = (CLpop × (BW/70)0.75) × (eGFR/100)0.378) for patients without CRRT and CLi = (CLpop × (BW/70)0.75) × 0.9 for patients with CRRT, where CLpop, V1pop, Qpop, and V2pop are 6.82 L/h, 40.6 L, 1 L/h, and 9.2 L respectively normalized to a 70-kg subject. Continuous infusion, 60 and 120 mg/kg per day, is the most adequate dosing regimen to attain the target of 50% fT > MIC and 100% fT > MIC for patients infected by bacteria with high minimum inhibitory concentration (MIC) value (> 4 mg/L) without risk of accumulation except in children with severe renal failure. CONCLUSION: Continuous infusion allows reaching the fT > MIC targets safely in children with normal or increased renal clearance.

Impact of antiretroviral treatment on height evolution of HIV infected children.

BACKGROUND: Antiretroviral treatment (ART) has been shown to have a beneficial effect on the weight evolution but its effect on height remains unclear. We described patterns of height evolution and identified predictors of catch-up growth in HIV-infected children on ART. METHODS: To describe the height evolution from birth to adulthood, we developed a nonlinear mixed effect model using data from perinatally HIV-infected children who initiated ART from 1999 to 2013 in a prospective cohort study in Thailand. The main covariates of interest were: sex, ART regimen (dual nucleoside reverse-transcriptase inhibitor, non-nucleoside reverse transcriptase inhibitor (NNRTI)-, or protease inhibitor (PI)-based), baseline CD4 percentage, HIV-RNA load and CDC HIV Classification stage and occurrence of AIDS-defining events. RESULTS: A total 477 children (43% boys) contributed 18,596 height measurements over a median duration of 6.3 years on ART (interquartile range, 3.0 to 8.3). At ART initiation, median age was 6.2 years (1.8 to 9.6), 16% of children were underweight (weight-for-age z-score < - 2), 49% presented stunting (height-for-age z-score < - 2), and 7% wasting (weight-for-height z-score < - 2). The most frequent regimen at ART initiation was NNRTI-based (79%). A model with 4 components, birth length and 3 exponential functions of age accounting for the 3 growth phases was developed and show that the height-growth velocity was inversely associated with the age at ART initiation, the adult height was significantly lower in those who had experienced at least one AIDS-defining event while, as expected, the model found that adult height in females was lower than in males. Age at ART initiation, type of ART regimen, CDC stage, CD4 percentages, and HIV-RNA load were not associated with the final height. CONCLUSIONS: The younger the children at ART initiation, the greater the effect on height-growth velocity, supporting the World Health Organization's recommendation to start ART as early as possible. However, final adult height was not linked to the age at ART initiation.

Population pharmacokinetics of enoxaparin in early stage of paediatric liver transplantation.

AIMS: Preventing post-liver transplantation (LT) hepatic artery and portal vein thrombosis includes enoxaparin administration. Enoxaparin pharmacokinetics (PK) has not been investigated in children following LT. We described an enoxaparin PK model in 22 children the first week following LT. METHODS: Anti-Xa activity time-courses were analysed using a nonlinear mixed effects approach with Monolix version 2016R. RESULTS: Anti-Xa activity time-courses were well described by a one-compartment model with first order absorption and elimination. Bodyweight prior to surgery (BWPREOP ) and the related postoperative variation (BW(t)) were the main covariates explaining CL and V between subject variabilities. Parameter estimates were CLi  = CLTYP * (BWPREOP /70)3/4 ; Vi  = VTYP * (BW(t)/70)1 ; where typical clearance (CLTYP ) and typical volume of distribution (VTYP ) were 1.23 l h-1 and 14.6 l, respectively. Standard dosing regimens of 50 IU kg-1  12 h-1 were insufficient to reach the target range of anti-Xa activity of 0.2-0.4 IU ml-1 . Specifically, seven children (32%) never attained the target range during the whole period of treatment and all children were at least once underdosed. According to the final results, we simulated individualized dosing regimens within 4 h following the first administration. More than 100 IU kg-1  12 h-1 are suggested to reach the target range of anti-Xa activity of 0.2-0.4 IU ml-1 from the first day. CONCLUSION: Thanks to this model, the initial and maintenance doses could be assessed to rapidly achieve the target range. Higher doses per kg, especially in the youngest children, are suggested.

Pharmacokinetics of cefuroxime in infants and neonates undergoing cardiac surgery.

AIMS: Very little data exist regarding the effect of cardiopulmonary bypass (CPB) on cefuroxime (CXM) pharmacokinetics in children less than one year of age. METHODS: 50 mg kg-1 CXM i.v. after induction were followed by 75 mg kg-1 into the CPB circuit. In 42 patients undergoing cardiac surgery, 15-20 samples were obtained between 5 and 360 min after the first dose. Total CXM concentrations were measured by high-performance liquid chromatography and a pharmacokinetic/pharmacodynamic (PK/PD) modelling was performed. RESULTS: Using a fixed protein binding of 15.6% for CXM, peak plasma concentrations of unbound CXM were 229 ± 52 µg ml-1 after the first bolus and 341 ± 86 µg ml-1 on CPB. Nadir concentrations before CPB were 69 ± 20 µg ml-1 and six hours later decreased to 41 ± 19 µg ml-1 with and 24 ± 14 µg ml-1 without CPB. A two-compartment model was fitted with the main covariates body weight, CPB and postmenstrual age (PMA). PK parameters were as follows: systemic clearance, 5.15 [95% CI 4.5-5.8] l h-1 ; central volume of distribution, 11.25 [9.41-13.09] l; intercompartmental clearance, 18.19 [14.79-21.58] l h-1 ; and peripheral volume, 17.07 [15.7-18.5] L. ƒT > MIC of 32 µg ml-1 for an 8-h time period was between 70 and 100% (2.5-10 kg BW). According to our simulation, 25 mg ml-1 CXM as a primary bolus and into the prime plus a 5 mg kg-1  h-1 infusion maintain CXM concentrations continuously above 32 µg ml-1 . CONCLUSIONS: The routine dosing regimen provided was sufficient for prophylaxis, but continuous dosing can provide a higher percentage of ƒT > MIC.

Epinephrine Dose Has a Preventive Effect on the Occurrence of Stress Ulcer-Induced Gastrointestinal Bleeding in Critically Ill Patients.

BACKGROUND: Epinephrine may impair splanchnic blood flow, but the impact of epinephrine dose on the occurrence of clinically significant gastrointestinal bleeding (CSGB) caused by stress ulcer remains unclear. We investigated the effect of epinephrine dose on the occurrence of stress ulcer-related CSGB in intensive care unit (ICU) patients. METHODS: In this prospective, observational, cohort study conducted in a French teaching hospital, 40 consecutive ICU patients receiving epinephrine infusion in whom a stress ulcer was diagnosed by an upper gastrointestinal endoscopy were included, from February 2010 to July 2015. The effects of epinephrine dose, and other covariates, on the occurrence of stress ulcer-related CSGB were analyzed using a multiple logistic regression model for repeated measures: At each observation, each patient serves as his own control. RESULTS: A total of 1484 time-dependent epinephrine dose modifications were available for analysis. The median epinephrine dose rate was 0.8 (0-9.5) mg/h, and the median epinephrine cumulative dose was 44.8 (2.6-2343) mg. Epinephrine, expressed as the average dose per day at time t, had a significant protective effect on the occurrence of stress ulcer (odds ratio 0.22; 95% confidence interval (CI), 0.12-0.38; p < 0.0001, for a log10 increase of epinephrine dose). Enteral feeding had also a protective effect (odds ratio 0.55; 95% CI 0.41-0.72; p < 0.0001, for a log10 increase of kcal/day). Only renal replacement therapy increased the occurrence of stress ulcer in the model. CONCLUSIONS: An increase in the average dose of epinephrine per day increased the time to occurrence of stress ulcer in critically ill patients.

Population Pharmacokinetic Modeling of Tenofovir in the Genital Tract of Male HIV-Infected Patients.

The aims of this study were to describe the blood plasma (BP) and seminal plasma (SP) pharmacokinetics of tenofovir (TFV) in HIV-1-infected men, to assess the role of genetic polymorphism in the variability of TFV transfer into the male genital tract, and to evaluate the impact of TFV SP exposure on seminal plasma HIV load (spVL). Men from the Evarist-ANRS EP 49 study treated with TFV as part of their antiretroviral therapy were included in the study. A total of 248 and 217 TFV BP and SP concentrations from 129 men were available for the analysis. For pharmacogenetic assessment, a total of 121 single nucleotide polymorphisms (SNP) were genotyped. Data were analyzed using a nonlinear mixed-effects modeling approach. TFV pharmacokinetics were best described by a two-compartment model for BP and by an effect compartment with different input and output constants for SP. TFV exposures (area under the concentration-time curve from 0 to 24 h [AUC0-24]) were higher in SP than in BP (median AUC0-24, 7.01 versus 2.97 mg · liter-1 · h, respectively). The median (range) SP-to-BP AUC0-24 ratio was 2.24 (0.53 to 34.13). After correction for multiple testing, none of the SNPs were significantly associated with the TFV transfer rate constant. The impact of the TFV SP AUC0-24 or TFV SP-to-BP AUC0-24 ratio on spVL was not significant (P = 0.808 and 0.768, respectively). This is the first population model describing TFV pharmacokinetics in the male genital tract. TFV SP concentrations were higher than BP concentrations. Despite TFV SP exposures being higher than BP exposures, an spVL was detectable for 12.2% of the men.