Relationship between clinical remission of perianal fistulas in Crohn's disease and serum adalimumab concentrations: A multi-center cross-sectional study.

BACKGROUND: Crohn's disease (CD) is complicated by perianal fistulas in approximately 20% of patients. Achieving permanent fistula closure remains a challenge for physicians. An association between serum anti-tumor necrosis factor-α concentrations and clinical outcomes in patients with CD has been demonstrated; however, little information is available on serum adalimumab (ADA) concentrations and remission of perianal fistulas in such patients. AIM: To study the relationship between serum ADA concentrations and clinical remission of CD-associated perianal fistulas. METHODS: This cross-sectional study of patients with CD-associated perianal fistulas treated with ADA was performed at four French hospitals between December 2013 and March 2018. At the time of each serum ADA concentration measurement, we collected information about the patients and their fistulas. The primary study endpoint was clinical remission of fistulas defined as the absence of drainage (in accordance with Present's criteria), with a PDAI ≤ 4, absence of a seton and assessment of the overall evaluation as favorable by the proctologist at the relevant center. We also assessed fistula healing [defined as being in clinical and radiological (magnetic resonance imaging, MRI) remission] and adverse events. RESULTS: The study cohort comprised 34 patients who underwent 56 evaluations (patients had between one and four evaluations). Fifteen patients had clinical remissions (44%), four of whom had healed fistulas on MRI. Serum ADA concentrations were significantly higher at evaluations in which clinical remission was identified than at evaluations in which it was not [14 (10-16) vs 10 (2-15) µg/mL, P = 0.01]. Serum ADA concentrations were comparable at the times of evaluation of patients with and without healed fistulas [11 (7-14) vs 10 (4-16) µg/mL, P = 0.69]. The adverse event rate did not differ between different serum ADA concentrations. CONCLUSION: We found a significant association between high serum ADA concentrations and clinical remission of CD-associated perianal fistulas.

Development of a dosing-adjustment tool for fluoroquinolones in osteoarticular infections: The Fluo-pop study.

Fluoroquinolones efficacy depend on both the drug exposure and the level of drug resistance of the bacteria responsible for the infection. Specifically for the Staphylococcus species, which is the microorganism mainly involved in osteoarticular infections (OAI), in-vitro data reported that an AUC/MIC ratio above 115 h maximizes drug efficacy. However, data on OAI patients are lacking and a simple approach to access AUCs is still a clinical issue. We conducted a prospective, single-center study in 30 OAI patients hospitalized in the Rennes University Hospital to model ofloxacin pharmacokinetics and to define a limited sampling strategy (LSS) suitable for ofloxacin and levofloxacin treatments. Modeling was conducted with the Monolix software. The final model was externally validated using levofloxacin data. Monte-Carlo simulations were used to evaluate the probability of target attainment (PTA) of different dosing regimens. Two hundred and ninety-seven (297) ofloxacin concentrations were available for the pharmacokinetic modeling. Ofloxacin pharmacokinetics was best described using a bicompartmental model with a first order elimination, and a transit compartment model absorption. CKD-EPI and sex explained half of ofloxacin pharmacokinetic variability. For LSS, the 0, 1 h and 3 h sampling scheme resulted in the best approach both for BID and TID dosages (R2 adjusted = 91.1% and 95.0%, outliers = 4.8% and 5.0%, respectively). PTA allows choosing the best drug and dosage according to various hypotheses. A simple 3-sample protocol (pre-dose, 1 h after intake and 3 h after intake) to estimate ofloxacin and levofloxacin AUC allows optimal drug dosage for the treatment of osteoarticular infections.

Cumulative Exposure to Infliximab, But Not Trough Concentrations, Correlates With Rate of Infection.

BACKGROUND & AIMS: Infliximab increases the risk of infection in patients with inflammatory bowel diseases (IBD), but there is controversy over the relationship between drug concentration and infections. We aimed to assess factors associated with infection in infliximab-treated patients, including pharmacokinetic features. METHODS: We collected data from 209 patients with IBD (102 men; mean age, 39 y; 159 with Crohn's disease; 54 received combination therapy) who received an infliximab maintenance regimen from November 2016 through April 2017 in France. Data were collected from each infusion visit (total of 640 infusions). Infliximab exposure was estimated based on the area under the curve (AUC) of drug concentration in pharmacokinetic models; individual exposures over the 6-month period were estimated based on the sum of the AUC (ΣAUC). RESULTS: The mean infliximab trough level was 5.46 mg/L, and the mean ΣAUC was 3938 ± 1427 mg.d/L. A total of 215 infections were collected from the 640 infusion visits; 123 patients (59%) had at least 1 infection. Factors independently associated with infection after multivariate analysis were smoking (odds ratio [OR], 2.05; P = .046), IBD flare (OR, 2.71; P = .006), and a high ΣAUC of infliximab (above 3234 mg x d/L) (OR, 2.02; P = .02). The ΣAUC was higher in patients with an occurrence of infection (P = .04) and correlated with the number of infections (P = .04). Trough concentration of infliximab alone was not associated with infection. CONCLUSIONS: Almost two-thirds of patients treated with infliximab developed an infection; risk was individually correlated with cumulative increase in drug exposure, but not infliximab trough level.

Redefining Therapeutic Drug Monitoring of Tacrolimus in Patients Undergoing Liver Transplantation: A Target Trough Concentration of 4-7 ng/mL During the First Month After Liver Transplantation is Safe and Improves Graft and Renal Function.

BACKGROUND: Currently, the recommended tacrolimus (TAC) trough level (Cmin) after liver transplantation (LT) is 6-10 ng/mL (when associated in triple immunosuppressive therapy). However, few studies have achieved the lower limit of this range, especially below 7 ng/mL. This study evaluated the efficacy of a target TAC Cmin of 4-7 ng/mL after LT. METHODS: Of 1677 LTs performed between 2002 and 2017, 904 LT cases were analyzed. The cases were categorized into the following 3 groups and compared: low- (n = 247, 27.3%), intermediate- (n = 344, 37.9%), and high-exposure groups (n = 313, 34.5%) with TAC Cmin of 4-7 ng/mL, 7-10 ng/mL, and >10 ng/mL, respectively. In addition, propensity score matching was performed to reduce heterogeneity and population bias. RESULTS: At months 1 and 3, when compared with the 2 other groups, the low-exposure group had similar grafts (P = 0.75) and patient (P = 0.77) survival, but lower alanine aminotransferase (P < 0.001), bilirubin (P < 0.001), international normalized ratio (P = 0.046), and creatinine (P < 0.001) levels. After propensity score matching, the bilirubin (P < 0.001) and creatinine (P = 0.001) levels in the low-exposure group still improved at months 3, but the graft (P = 0.86) and patient (P = 0.99) survival were still similar. CONCLUSIONS: A TAC Cmin of 4-7 ng/mL seems safe and capable of improving graft and kidney function. This finding should be confirmed in a prospective randomized trial.

Pharmacogenetic-Whole blood and intracellular pharmacokinetic-Pharmacodynamic (PG-PK2-PD) relationship of tacrolimus in liver transplant recipients.

Tacrolimus (TAC) is the cornerstone of immunosuppressive therapy in liver transplantation. This study aimed at elucidating the interplay between pharmacogenetic determinants of TAC whole blood and intracellular exposures as well as the pharmacokinetic-pharmacodynamic relationship of TAC in both compartments. Complete pharmacokinetic profiles (Predose, and 20 min, 40 min, 1h, 2h, 3h, 4h, 6h, 8h, 12h post drug intake) of twice daily TAC in whole blood and peripheral blood mononuclear cells (PBMC) were collected in 32 liver transplanted patients in the first ten days post transplantation. A non-parametric population pharmacokinetic model was applied to explore TAC pharmacokinetics in blood and PBMC. Concurrently, calcineurin activity was measured in PBMC. Influence of donor and recipient genetic polymorphisms of ABCB1, CYP3A4 and CYP3A5 on TAC exposure was assessed. Recipient ABCB1 polymorphisms 1199G>A could influence TAC whole blood and intracellular exposure (p<0.05). No association was found between CYP3A4 or CYP3A5 genotypes and TAC whole blood or intracellular concentrations. Finally, intra-PBMC calcineurin activity appeared incompletely inhibited by TAC and less than 50% of patients were expected to achieve intracellular IC50 concentration (100 pg/millions of cells) at therapeutic whole blood concentration (i.e.: 4-10 ng/mL). Together, these data suggest that personalized medicine regarding TAC therapy might be optimized by ABCB1 pharmacogenetic biomarkers and by monitoring intracellular concentration whereas the relationship between intracellular TAC exposure and pharmacodynamics biomarkers more specific than calcineurin activity should be further investigated.

Modelling of the Time-Varying Pharmacokinetics of Therapeutic Monoclonal Antibodies: A Literature Review.

Therapeutic monoclonal antibodies (mAbs) are increasingly used to treat a variety of conditions. The sources of their interindividual pharmacokinetic (PK) variability have been extensively studied, but few data on their intraindividual PK variability are available. In this article, we reviewed the published population compartmental models used to describe the time-varying PK of mAbs in clinical settings. Of 189 publications, 13 report the use of time-varying parameters and 30 describe the effects of antidrug antibody (ADA) development. Currently published time-varying models mainly describe fast decreases in clearance due to target-mediated elimination or slow decreases in clearance owing to cachexia reduction. Immunogenicity models mostly describe 'on-off' increases of clearance due to a rapid elimination of mAbs-ADA complexes. Some more sophisticated models attempted to decipher the time course of immunogenic response, notably by accounting for the time of onset and progressive increase in ADA production. Currently available time-varying and immunogenicity models are empirical approximations of the complex mAb disposition, but they emphasize the necessity to account for the temporal variations of mAb PK in model building. The clinical implications of the time-varying PK of mAbs are not fully understood, but some publications reported a link between clearance decrease and disease improvement. The future perspectives offered by this knowledge include the possibility to adapt the regimen to the disease and the patients' state, and also to immune status, and to monitor their evolution by monitoring PK variations.

Intra-tracheal amikacin spray delivery in healthy mechanically ventilated piglets.

BACKGROUND: Nebulization during mechanical ventilation is impeded by large extra-pulmonary drug deposition and long administration durations which currently limit implementation of inhaled antibiotic therapy. Direct intra-tracheal delivery using a sprayer represents an appealing alternative investigated in small animal models, but large animal data are lacking. METHODS: Amikacin was administered through intravenous infusion (20 mg/kg), nebulization (60 mg/kg) and direct intra-tracheal spray (30 mg/kg) to 10 intubated piglets, in a randomized cross-over design. Amikacin concentrations were measured in the serum and pulmonary parenchyma. Anatomic deposition was investigated using immuno-histochemistry. RESULTS: Spray delivery resulted in higher amikacin outputs than nebulization and infusion. Pulmonary inhaled delivery techniques yielded much higher lung concentrations and much lower serum concentrations than intravenous infusion. However, unlike nebulization and infusion, intra-tracheal spray delivery was associated with more than 100- and 1000-fold variability in lung concentrations between and within animals. Amikacin specific immuno-histochemistry showed consistent bronchial and alveolar drug deposition with all modalities. CONCLUSION: Nebulization remains the most reliable and simple technique to deliver inhaled amikacin uniformly to the lung during mechanical ventilation. Further development of tracheal sprays is required to take advantage of potential benefits related to high drug output and low extra-pulmonary deposition in large animals.

Pharmacokinetic Parameters of Infliximab Influence the Rate of Relapse After De-Escalation in Adults With Inflammatory Bowel Diseases.

This study aimed at exploring the link among individual concentrations, pharmacokinetic parameters, and the probability of relapse after de-escalation in a real-world prospective cohort of patients with inflammatory bowel disease (IBD) who underwent infliximab treatment de-escalation. Ninety-one patients were included. A time-varying compartment model was used to estimate individual pharmacokinetic parameters and trough concentrations. A Cox model was implemented to explore the parameters influencing the probability of relapse after de-escalation. Volume, clearance, and trough before and after de-escalation were linked to the relapse risk at the univariate step. Independent predictors of relapse were tobacco use and/or ulcerative colitis (P = 0.0093), a higher C-reactive protein (CRP; P = 0.00064), and an infliximab trough < 2.4 µg/mL after de-escalation (P = 0.0001). Patients with trough > 5.7 µg/mL are eligible to de-escalation, but infliximab pharmacokinetics is highly variable in time. Therefore, drug monitoring is mandatory after de-escalation to maintain trough > 2.4 µg/mL. Clearance monitoring seems an appealing approach for patient selection and relapse prediction.

Tacrolimus diffusion across the peripheral mononuclear blood cell membrane: impact of drug transporters.

Measuring tacrolimus (TAC) concentration in peripheral blood mononuclear cells (PBMCs) could better reflect the drug effect on its target (calcineurin (CaN) in lymphocytes) than whole blood concentrations. Mechanisms influencing TAC diffusion into PBMC are not well characterized. This work aimed at describing, ex vivo, TAC diffusion kinetics into PBMC and investigating the contribution of membrane transporters to regulate TAC intracellular concentration as well as the impact on CaN activity. PBMCs were incubated with TAC for 5 min to 4 h and under several experimental conditions: 37 °C (physiological conditions), 4 °C (inhibition of influx and efflux active transport), 37 °C + transporter inhibitors (verapamil, carvedilol, and probenecid and bromosulfophthalein, respectively, inhibitors of P-gp, OAT, and OATP). TAC concentration and CaN activity were measured in PBMC using liquid chromatography coupled with mass spectrometry. TAC intra-PBMC concentration was maximal after 1 h of incubation. Mean TAC PMBC concentrations were significantly lower in samples incubated at 4 °C compared to the 37 °C groups. Addition of verapamil slightly increased TAC accumulation in PBMC while other inhibitors had no effect. A significant correlation was found between TAC intra-PBMC concentration and the level of inhibition of CaN. Using an ex vivo cellular model, these results suggest that P-gp is involved in the drug efflux from PBMC while influx active transporters likely to regulate TAC intra-PBMC disposition remain to be identified. TAC concentration in PBMC is correlated with its pharmacodynamic effect. Then, TAC intra-PBMC concentration appears to be a promising biomarker to refine TAC therapeutic drug monitoring.

Pharmacogenetics of Membrane Transporters of Tacrolimus in Solid Organ Transplantation.

Membrane transporters play an essential role in the pharmacokinetics of drugs as they mediate exchanges between biological compartments. Tacrolimus is characterized by wide interpatient variability in terms of its pharmacokinetics that may in part be due to genetic factors. The pharmacogenetics of drug transporters is therefore a promising area to explore in the clinical pharmacology of tacrolimus. The aim of this review is to provide an overview of currently available data regarding the pharmacogenetics of membrane transporters that may be involved in the interindividual variability of the response to tacrolimus. Several genetic variants in genes coding for influx or efflux membrane transporters (e.g. ABCB1, ABCC2, ABCC8, SLC30A8, SLCO1B1/3, SLC28A1, SLC22A11, and SLC28A3) have been associated with tacrolimus pharmacokinetics variability or the occurrence of toxicity; however, there is still a degree of controversy as to the impact of these variants in vivo and further investigations are needed to confirm these results in larger cohorts and to validate the relevance of such genetic biomarkers for personalization of immunosuppressive therapy in solid organ transplantations. The relationship between transporter polymorphisms and the intracellular concentration of tacrolimus should also be further investigated. Finally, the main challenge could be elucidation of the interplay of biological mechanisms underlying genetic variations that alter the drug concentration or its clinical effect.

Tacrolimus overexposure in kidney transplant recipients during the first post-operative week: caution is required in older patients.

In liver transplantation, tacrolimus trough concentrations (Cmin) above 20 ng/mL during the first days led to worse outcome at 1 year but data in the kidney transplant (KT) era are scarce. The aim of this study was to evaluate the impact of tacrolimus overexposure during the first week post-transplantation on the kidney function (KF) of KT recipients. In this retrospective study, 105 KT recipients were attributed to overexposure group (OG) or normal group according to their Cmin during the first week of treatment. KF was evaluated by comparing the rate of delayed graft function (DGF) and by collecting plasma creatinine from day 1, 2, 3, 4, 5, 6, 7, 14, 21, 28 and at 1 year. Risk factors for developing DGF were also investigated using a multivariate model. DGF was more frequent in OG (43% of patients; P = 0.027) which has higher plasma creatinine on day 7, 14, and 21. OG patients were older with more extended criteria donor's grafts. In the multivariate analysis, only cold ischemia time (CIT) remained associated with DGF (OR = 1.003), while TAC overexposure did not reach significance (P = 0.06; OR = 3.9). In this study, we confirmed the predominant role of CIT as a risk factor for the onset of DGF in kidney transplantation. 43% of KT recipients were overexposed with more DGF, especially older patients.

Predictors of relapse following infliximab de-escalation in patients with inflammatory bowel disease: the value of a strategy based on therapeutic drug monitoring.

BACKGROUND: There are limited data concerning infliximab drug monitoring during de-escalation of the treatment of inflammatory bowel disease (IBD). AIM: To define the rate and the predictors of relapse following infliximab de-escalation in IBD patients in remission. METHODS: All IBD patients at a single referral centre in clinical and biological remission and in whom the dose of infliximab had been de-escalated were included. Patients in remission with a high trough level of infliximab (>7 mg/L) were considered to be trough level-based de-escalation patients. The data were retrieved from a prospective IBD database. Actuarial analysis was performed for statistical purposes. RESULTS: A total of 146 de-escalations were performed in 96 patients (Crohn's disease/ulcerative colitis: 68%/32%); 54 (37%) were based on clinical remission only, and 92 (63%) were based on clinical remission associated with a trough level above 7 mg/L. The cumulative probabilities of relapse following infliximab de-escalation were 16% and 47% at 1 and 2 years, respectively. Ulcerative colitis was associated with an increased risk of relapse (HR = 3.2, P = 0.005). Conversely, combination therapy at infliximab initiation (HR = 0.39, P = 0.0110) and trough level-based de-escalation were associated with decreased risk of relapse (HR = 0.45, P = 0.024). Trough levels before and after de-escalation were well correlated; a decrease by half was observed following a 2-week interval increase or a half-dose decrease. CONCLUSION: The use of trough levels to assess the feasibility of dose de-escalation seems to be a prerequisite for decreasing the risk of relapse.

Tacrolimus Concentrations Measured in Excreted Bile in Liver Transplant Recipients: The STABILE Study.

PURPOSE: Tacrolimus (TAC) is the main immunosuppressive drug in liver transplantation. Despite intensive therapeutic drug monitoring (TDM) that relies on whole blood trough concentration (TACblood), patients still present with acute cellular rejection or TAC-related toxic effects with concentrations within the therapeutic range. TAC concentration in peripheral blood mononuclear cells (TACPBMC) is considered as an efficient surrogate marker of TAC efficacy. However, it is still not applicable in daily practice. New TDM methods are therefore needed, especially during the early postoperative period. TAC is metabolized in the liver and eliminated through biliary excretion. We therefore hypothesised that TAC concentration measured in excreted bile (TACbileC) could be a relevant surrogate marker of its efficacy. METHODS: The Therapeutic Drug Monitoring of Tacrolimus Biliary Concentrations for Liver-Transplanted Patients (STABILE) study is a prospective monocentric trial. During the 7 first days after TAC therapy initiation, TACbileC was measured. The correlation between TACbileC and TACPBMC as well as between TACblood and TACPBMC was assessed. The correlations between TACbileC and liver graft function parameter or with occurrence of neurologic toxic effects were also evaluated. FINDINGS: Between May 2016 and April 2017, 41 patients were analyzed. TACbileC was significantly correlated with TACPBMC (r = 0.25, P = 0.007). However, a better correlation was found between TACPBMC and TACblood (r = 0.53, P < 0.001) and was confirmed in multivariate analysis. However, only TACbileC was significantly correlated with liver graft function, such as factor V (r = 0.40, P = 0.009) or bilirubin level (r = 0.21, P = 0.01), and significantly lower in patients presenting with neurologic toxic effects (P < 0.001). Receiver operating characteristic curve analysis found that a TACbileC level lower than 0.20 ng/mL on day 2 after TAC therapy initiation was a good predictive marker of occurrence of neurotoxic effects (AUC = 0.81). IMPLICATIONS: TACbileC is not a better surrogate maker of TAC activity than TACblood. However, TACbileC could help predict the occurrence of TAC toxic effects when a T-tube is inserted. ClinicalTrials.gov identifier: NCT02820259.

Modeling Immunization To Infliximab in Children With Crohn's Disease Using Population Pharmacokinetics: A Pilot Study.

Background: Antidrug antibodies (ADAs) dramatically increase infliximab clearance and are responsible for underexposure to the drug, leading to treatment failure. This pilot study aimed at developing a population pharmacokinetic model to detect and describe an early increase in infliximab clearance due to ADA. Methods: Twenty children with Crohn's disease (CD) were followed for 1 year or until treatment failure. Infliximab trough concentration, ADA, C-reactive protein (CRP), and Paediatric Crohn's Disease Activity Index (PCDAI) were recorded at each visit. A time-varying clearance population pharmacokinetic model was built to detect and describe an increase in infliximab clearance, independent from ADA testing. Factors associated with clearance variation and the relationships between infliximab concentrations, clearance variation, and clinical response were investigated. Results: The model detected important increases in clearance in 4 patients. These patients had suboptimal early response, with higher mean PCDAI (P = 0.0086) and CRP (P = 0.028) compared with other patients. Two of them had detectable ADA. Clearance increase as described by the model and lower infliximab trough concentration at week 2 were associated with poorer outcomes in a multivariate Cox model (P = 0.001 and P = 0.0048, respectively). Conclusions: Being able to detect an increase in infliximab clearance, this model could allow the early detection of immunization to infliximab and therefore could help with dose adjustment in patients with CD. Moreover, the results suggest that clearance variations could be used as a predictive marker of clinical response. These findings need to be confirmed in a larger cohort, however, and predictive factors of clearance increase have to be investigated.

High Intrapatient Variability of Tacrolimus Exposure in the Early Period After Liver Transplantation Is Associated With Poorer Outcomes.

BACKGROUND: Tacrolimus (TAC) is the cornerstone of immunosuppressive regimen in liver transplantation (LT). Its pharmacokinetics is characterized by a high interpatient and intrapatient variability (IPV) leading to an unpredictable dose-response relationship. The aim of our study was to evaluate the impact of TAC IPV (IPV) on graft and patient outcomes after LT. METHODS: We retrospectively analyzed 812 LT recipients treated with TAC. The IPV of TAC concentrations was estimated by calculating the coefficient of variation (CV) of whole blood trough concentrations. Patients were categorized in 2 groups: low IPV (CV < 40%) and high IPV (CV ≥ 40%). RESULTS: There were significantly more neurologic complications (31.2% vs 16.6%, P < 0.001), cardiovascular complications (19.7% vs 9.7%, P < 0.001), and acute renal failure requiring dialysis (8.5% vs 2.2%, P < 0.001) in the high CV group than in the low CV group. Moreover, graft survival was significantly poorer in the high CV group (hazard ratio, 1.42; 95% confidence interval, 1.04-1.95; P = 0.03). A pretransplantation elevated Model for End-Stage Liver Disease score (P < 0.001) and Child-Pugh grade (P < 0.001) were identified as risk factors for presenting a high CV. CONCLUSIONS: A high CV of TAC concentrations was found to be predictive of TAC-related toxicity and poorer survival.

Ex Vivo Model to Decipher the Impact of Extracorporeal Membrane Oxygenation on Beta-lactam Degradation Kinetics.

BACKGROUND: As a consequence of drug sequestration, increase in volume of distribution, or alteration of elimination, extracorporeal membrane oxygenation (ECMO) might lead to inadequate plasma concentrations of vital drugs. The aim of this experimental study was to develop an ex vivo model to better characterize the impact of ECMO procedure on beta-lactam antibiotics pharmacokinetics. METHODS: Plasma concentrations of cefotaxime, ceftazidime, cefepime, piperacillin, oxacillin, amoxicillin, and ceftriaxone were measured in an ex vivo ECMO circuit primed with whole human blood and compared with controls stored in glass tubes and polyvinyl chloride tubing. Serial blood samples were collected over 48 hours, and the concentrations of beta-lactam antibiotics were quantified using a validated high-performance liquid chromatography assay. The concentrations' decay rate over time was compared between the ECMO circuits and controls using nonlinear mixed-effect modeling. RESULTS: Cefotaxime concentrations decreased markedly: 86% of the initial concentration remained after 4 hours and only 21% after 48 hours (P < 0.05 for the comparison in rate of decrease with both glass and polyvinyl chloride controls). There was no difference in the rate of decrease between ECMO circuit and controls for the other beta-lactam antibiotics. The average drug recoveries from the ECMO circuits at 48 hours were as follows: ceftazidime, 73%; cefepime, 67%; piperacillin, 71%; oxacillin, 46%; and amoxicillin, 72%. Concentrations of ceftriaxone remained stable throughout the 48-hour study both in ECMO circuits and in controls. CONCLUSIONS: Significant losses of cefotaxime were observed, whereas ceftazidime, cefepime, piperacillin, oxacillin, and amoxicillin decrease was moderate and similar to that of the control group, and ceftriaxone concentrations remained unchanged. These results are reassuring for the use of beta-lactam antibiotics in critically ill patients treated with ECMO.

A high performance liquid chromatography tandem mass spectrometry for the quantification of tacrolimus in human bile in liver transplant recipients.

Tacrolimus whole-blood concentrations imperfectly reflect concentrations at the effect site. Tacrolimus concentrations in the transplanted organ could be more relevant to predict rejection events. Because liver biopsy cannot be repeatedly performed after liver transplantation, we suggested measuring tacrolimus in the bile to have a cost-effective and clinically implementable surrogate marker of intra-hepatic tacrolimus concentration. We developed and fully validated a liquid chromatography-tandem mass spectrometry method for the determination of tacrolimus in human bile. Sample purification was achieved using protein precipitation and liquid-liquid extraction with ethyl-acetate. Gradient elution was performed using a C18 analytical column with a 5min run-time. The method was linear from 0.5ng/mL to 20ng/mL. In this concentration range, within-day and between-day precisions as well as overall bias were within ±15%. Matrix effect was fully corrected by the internal standard (ascomycin). The assay was optimized to achieve good selectivity in this complex biological matrix. Tacrolimus was found to be stable in bile stored 6 months at -80°C, after 3 freeze and thaw cycles, 20h at room temperature and 24h in extracts kept at 15°C in the auto-sampler. The method was applied to quantify tacrolimus in bile from liver transplant recipients. It allowed getting preliminary data about tacrolimus excretion profile in bile and showed the lack of correlation between tacrolimus whole blood concentration and tacrolimus liver exposition. This alternative and innovative analytical approach of tacrolimus bio-analysis appears suitable for further studies evaluating relevance of biliary tacrolimus concentration as a new pharmacological marker of immunosuppressive activity.

Aerosol Therapy in Adults Receiving High Flow Nasal Cannula Oxygen Therapy.

BACKGROUND: High flow nasal cannula oxygen therapy (HFT) is increasingly used in intensive and emergency care departments. Patients suffering from respiratory failure, who are likely to benefit from HFT, may require aerosolized bronchodilators; therefore, combining nebulization with HFT may be relevant. This study aimed to identify the optimal settings for the implementation of nebulization within an adult HFT circuit. METHODS: We assessed the mass and the particle size distribution of the aerosol emitted from the nasal cannula (inhalable mass) using mesh- and jet-nebulizers placed at various positions in the HFT circuit. Thereafter, the most relevant combination was used to evaluate the mass of salbutamol delivered downstream of an anatomical model reproducing aerosol deposition and leakage at the nasal and pharyngeal levels (respirable mass). The influence of HFT flow rate (30, 45, and 60 L/min), of breathing pattern (quiet and respiratory distress pattern) as well as of opened and closed mouth breathing was assessed. RESULTS: The most efficient position was that of a nebulizer placed upstream from the humidification chamber (inhalable mass ranging from 26% to 32% of the nebulizer charge). Using a mesh nebulizer, we observed a respirable mass ranging from 2% to 10% of the nebulizer charge. Higher HFT flow rates and open mouth breathing were associated with a lower efficiency. Simulating respiratory distress (i.e., increasing the simulated patient inspiratory flow) did not hamper drug delivery as compared to a quiet breathing pattern. CONCLUSIONS: Placing nebulizers within a HFT circuit upstream from the humidification chamber may enable to deliver clinically relevant masses of aerosol at the cannula outlet, but more importantly downstream of the nose and pharynx, even in case of high patients' inspiratory flow. This method of aerosol therapy is expected to produce a bronchodilatatory effect to be evaluated in the clinical settings.