Urinary methotrexate dosage in rheumatoid arthritis, in patients treated for at least 6 months: a potential marker of adherence.

OBJECTIVES: Non-adherence to rheumatoid arthritis (RA) treatments must be identified. A methotrexate (MTX) urinary dosage (METU) was recently developed. The aim of our study was to assess adherence to MTX in RA using METU in real-life conditions and to compare it with indirect adherence measurement technics. METHODS: We performed a cross-sectional study at Reims University Hospital. We included over 18-year-old patients with RA treated by MTX for more than 6 months. Patients were invited to complete demographic, clinical and psychological questionnaires and adherence measurement technics (Compliance Questionnaire of Rheumatology (CQR) and Medication Possession Ratio (MPR)). A urinary sample was collected to measure MTX and information about tolerance was evaluated through Methotrexate Intolerance Severity Score. RESULTS: 84 patients were included, 26 using oral MTX, 58 subcutaneous (SC) MTX. Among them, 73% were female, mean age was 61.5 years, MTX mean dose was 15 mg/week and 61.9% were treated by biological DMARDs (Disease Modifying Antirheumatic Drugs). 77 patients (91.7%) were adherent to treatment according to METU, whereas MPR and CQR reported less adherence (69.5% and 61.9%, respectively). MPR and METU were not significantly different in SC MTX users (p=0.059). Non-adherent patients had a higher number of tender joints and C reactive protein value (p<0.05). CONCLUSION: This is the first largest study evaluating MTX adherence in patients with RA using a urinary dosage. We identified that indirect adherence measurements did not reflect real-life adherence. It would be appreciable to realise METU, in a new study, in patients with RA with unexplained response to treatment, to consider it before escalating therapeutic strategy.

Comparison of two acquisition modes in mass spectrometry for quantification of 12 antibiotics, including beta-lactams, linezolid, fluoroquinolones and clindamycin: Multiple reactions monitoring (MRM) and fullMS/dd-MS2.

The quantification of antibiotics, using mass spectrometry, for monitoring therapeutic drugs is a key benefit in infection management. After an easy work-up of plasma samples, analysis were performed using both two widely used acquisition modes: MRM for the triple quadrupole spectrometer and fullMS/ddMS2 for the HRMS to quantify twelve antibiotics. Comparison between the two acquisition modes were performed. Validation parameters and sample values were used as comparison criteria. The results indicated a good correlation between the two methods, with an advantage for HRMS concerning the matrix effect. Both methods were applied to routine therapeutic drug monitoring.

Simultaneous quantification of 55 psychotropic drugs and metabolites in human plasma with a fast UPLC-MS/MS method.

OBJECTIVES: Therapeutic drug monitoring is strongly recommended for psychotropic drugs, which present a strong inter- and intra-individual variability due to multiple factors like inflammatory state, smoking, diet, drug interactions due to polypharmacy, and genetic profile. The aim of this study was to develop and validate a fast, simple, and sensitive method allowing the simultaneous quantification of a large number of psychotropic drugs. METHODS: After a simple sample preparation with a one-step protein precipitation, a total of 55 compounds, including 22 antidepressants, 18 antipsychotics, 2 other psychotropic drugs (bupropion and nefopam), and their metabolites, was separated on a Waters Acquity HSS T3 ultra-performance liquid chromatography column, and subsequently detected and quantified by a triple quadrupole Quantis mass spectrometer with electrospray ionization operated in positive mode. RESULTS: Total run time was only 5.7 min. Limits of detection ranged from 0.01 to 0.18 µg/L depending on compound. Measuring ranges were from 0.195 to 1000 µg/L depending on compound, and were defined according to therapeutic ranges. Inter- and intra-assay precisions values were less than 15 %. After validation, this method was successfully applied in daily practice for therapeutic drug monitoring of polymedicated psychiatric patients. CONCLUSION: We developed and validated one of the most sensitive and complete UPLC-MS/MS methods in psychopharmacology, allowing the simultaneous determination of 55 psychotropic drugs in only 5.7 min after a simple sample preparation. This method has been successfully used in daily practice for therapeutic drug monitoring of psychiatric patients and is especially useful in polymedicated patients.

A new pharmacokinetic model of urinary methotrexate to assess adherence in rheumatoid arthritis.

BACKGROUND AND OBJECTIVES: Methotrexate (MTX) is the first-line therapy for rheumatoid arthritis (RA). While therapeutic adherence is essential to successful management, no objective MTX assay is currently available. Using population pharmacokinetic modelling (PopPK), our objective was to describe the urinary MTX (MTXu) kinetics in treated patients and to evaluate its abilities to assess the MTX-adherence. METHODS: The association between urinary methotrexate level and methotrexate administration was assessed using a generalized linear model. Then, a population pharmacokinetic model was developed based on data from 59 patients using with Monolix 2021. R2. Simulations were run to establish a reference kinetic profile and evaluate the proportion of samples predicted as true positives. RESULTS: Compared to the control group, multivariate analysis showed that MTXu was independently associated with methotrexate administration (p < 0.0001) with a sensitivity and specificity greater than 99%. The final PopPK model selected was a two-compartment model with first-order absorption and elimination. Internal and external validation of the model met all predefined criteria. When using an analytical assay with a LOQ equal to 1 nM, the proportion of samples predicted as true positives is over 90%, as a function of MTX dose (7.5-25 mg/week) and post-administration sampling days (1-7 days). CONCLUSION: We developed a pharmacokinetic model able to describe expected patterns of urinary methotrexate. This allowed us to propose a new objective test of MTX adherence, which could help in routine practice to differentiate patients who are truly unresponsive to methotrexate from those who are unresponsive because of non-adherence.

Development and Validation of a Non-Targeted Screening Method for Most Psychoactive, Analgesic, Anaesthetic, Anti-Diabetic, Anti-Coagulant and Anti-Hypertensive Drugs in Human Whole Blood and Plasma Using High-Resolution Mass Spectrometry.

(1) Background: In toxicological laboratories, various screening methods can be used to identify compounds involved in intoxication. High-resolution mass spectrometry has been increasingly used in this context for the last years, because of its sensitivity and reliability. Here, we present the development and validation of a screening method that uses liquid chromatography coupled with a high-resolution mass spectrometer. (2) Methods: This method required only 100 µL of whole blood or plasma sample. Pretreatment consisted of a rapid and simple deproteinisation with methanol/acetonitrile and zinc sulphate. This new assay was validated according to international guidelines. (3) Results: To perform the method validation, 53 compounds were selected. The selection criteria were as follows: various chemical structures and therapeutic families (>15), large m/z distribution, positive or negative ionisation mode, and various elution times. The assays showed high selectivity and specificity, with optimal process efficiency. The identification limits, determined using predefined criteria, were established at sub-therapeutic or therapeutic concentrations. Applicability was evaluated using spiked plasma controls and external quality controls. (4) Conclusions: The new method was then successfully applied to routine clinical and forensic samples.

Renal impairment and abnormal liver function tests in pre-therapeutic phenotype-based DPD deficiency screening using uracilemia: a comprehensive population-based study in 1138 patients.

Background: Dihydropyrimidine dehydrogenase (DPD) deficiency screening is a pre-therapeutic standard to prevent severe fluoropyrimidine-related toxicity. Although several screening methods exist, the accuracy of their results remains debatable. In France, the uracilemia measurement is considered the standard in DPD deficiency screening. The objective of this study was to describe the hyperuracilemia (⩾16 ng/mL) rate and investigate the influence of hepatic and renal impairment in uracilemia measurements since the guidelines were implemented. Patients and methods: Using a cohort of 1138 patients screened between 18 October 2018 and 18 October 2021, basic demographic characteristics, date of blood sampling, and potential biological confounders including liver function tests [aspartate aminotransaminase (AST), alanine aminotransaminase (ALT), gamma-glutamyl transferase (γGT), alkaline phosphatase (ALP), and bilirubin] and estimated glomerular filtration rate (eGFR) were collected. The second same-patient uracilemia analysis was also performed. Temporal change was graphically represented while potential confounders were stratified to show linearity when suspected. Results: Hyperuracilemia was diagnosed in 12.7% (n = 150) samples with 6.7%, 5.4%, 0.5%, and 0.08% between 16 and 20 ng/mL, 20 and 50 ng/mL, 50 and 150 ng/mL, and >150 ng/mL, respectively. The median uracilemia concentration was 9.4 ng/mL (range: 1.2 and 172.3 ng/mL) and the monthly hyperuracilemia rate decreased steadily from >30% to around 9%. Older age, normalized AST, γGT, ALP results, bilirubin levels, and decreased eGFR were linearly associated with higher plasma uracil concentrations (all p < 0.001). In the adjusted multivariate linear model, AST, eGFR, and ALP remained associated with uracilemia (p < 0.05). When measured twice in 39 patients, the median uracilemia rate of change was -2.5%, which subsequently changed the diagnosis in nine patients (23.1%). Conclusions: Better respect of pre-analytical conditions may explain the steady decrease in monthly hyperuracilemia rates over the 3 years. Elevated AST, ALP levels, and reduced eGFR could induce a false increase in uracilemia and second uracilemia measurements modified the first DPD deficiency diagnosis in almost 25% of the patients.

Impact of Guidelines Regarding Dihydropyrimidine Dehydrogenase (DPD) Deficiency Screening Using Uracil-Based Phenotyping on the Reduction of Severe Side Effect of 5-Fluorouracil-Based Chemotherapy: A Propension Score Analysis.

Dihydropyrimidine dehydrogenase (DPD) deficiency is associated with severe fluoropyrimidines-induced toxicity. As of September 2018, French recommendations call for screening for DPD deficiency by plasma uracil quantification prior to all fluoropyrimidine-based chemotherapy. A dose reduction of fluoropyrimidine is recommended when uracil concentration is equal to or greater than 16 ng/mL. This matched retrospective study assessed the impact of DPD screening on the reduction of severe side effects and on the management of DPD-deficient patients. Using a propensity score, we balanced the factors influencing 5-Fluorouracil (5-FU) toxicity. Then, the severity scores (G3 and G4 severity as well as their frequency) of patients who did not benefit from DPD screening were compared with those of patients who benefited from DPD screening for each treatment cycle (from 1 to 4). Among 349 screened patients, 198 treated patients were included. Among them, 31 (15.7%) had DPD deficiency (median uracilemia 19.8 ng/mL (range: 16.1−172.3)). The median toxicity severity score was higher in the unscreened group for each treatment cycle (0 vs. 1, p < 0.001 at each cycle from 1 to 4) as well as the cumulative score during all courses of treatment (p = 0.028). DPD-deficient patients received a significantly lower dose of 5-FU (p < 0.001). This study suggests that pretherapeutic plasmatic uracil assessment, along with 5-FU dosage adjustment, may be beneficial in reducing 5-FU toxicity in real-life patients.

Incidence, associated factors, and effect on renal function of amoxicillin crystalluria in patients receiving high doses of intravenous amoxicillin (The CRISTAMOX Study): A cohort study.

Background: Amoxicillin crystalluria (AC), potentially responsible for acute kidney injury (AKI), is reported more and more frequently in patients treated with high doses of intravenous amoxicillin (HDIVA). The main objective of this study was to evaluate AC incidence in these patients. The secondary objectives were to identify factors associated with AC and to evaluate its impact on the risk of AKI. Methods: This multicentre, observational, cohort study was conducted between Mar 18, 2014 and Aug 16, 2019 in Dijon, Nancy, and Reims University Hospitals as well as Châlon-sur-Saône, Charleville-Mézières, and Troyes general hospitals in France. Adult patients (≥18 years) treated with HDIVA and having been tested for AC at least once during treatment were included. Clinical, biological, and therapeutic characteristics of the patients were collected. A univariable mixed logistic regression model assessed the factors associated with AC. A multivariable Cox model with AC as a time-dependent variable assessed the prognostic factors for AKI. ClinicalTrials.gov number: NCT02853292. Findings: Of the 112 included patients, 27 (24.1%, 95% CI [16.2-32.0]) developed at least one episode of AC within a mean of 5.1 days. The factors associated with its occurrence were the concomitant use of angiotensin converting enzyme (ACE) inhibitors (OR=4.6, 95% CI [2.2-9.3], p<0.0001) and the decrease of urinary pH (OR=2.1 for one pH point decrease, 95% CI [1.2-3.7], p=0.009). 20 patients (17.9%) presented with AKI, within a mean time of 10.9 days. The main factor associated with the occurrence of AKI was the occurrence of AC (aHR=7.4, 95% CI [2.5-22.2], p=0.0003). Interpretation: AC occurred in a quarter of patients treated with HDIVA and was highly prognostic of AKI. Funding: None.

Quantification of 15 Antibiotics Widely Used in the Critical Care Unit with a LC-MS/MS System: An Easy Method to Perform a Daily Therapeutic Drug Monitoring.

Potential under- or overdose of antibiotics may occur in intensive care units due to high variability in plasma concentrations. The risk is either treatment failure or toxicity. Thus, therapeutic drug monitoring of antibiotics may guide dosing adjustment, maximising antibacterial efficacy and minimising toxicity. The aim of this study was to develop and validate a method for the analysis of 15 antibiotics including beta-lactams, linezolid, fluoroquinolones, daptomycin, and clindamycin to have a complete panel in the management of infections. We proposed to develop a fast, sensitive, and quantitative method for the analysis of 15 antibiotics using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometer (UPLC-MS/MS) technology. this method required only 100 µL of plasma and consisted of a rapid liquid-liquid deproteinisation using methanol. Calibration curves ranged from 0.078 to 500 mg/L depending on the molecules, and were defined according to a therapeutic range. Inter- and intra-assay precisions values were less than 15%. This work described the development and the full validation of a precise, sensitive and accurate assay using UPLC-MS/MS technology. After validation, this new assay was successfully applied to routine therapeutic drug monitoring.

Alveolar hemorrhage due to marijuana smoking using water pipe made with plastic bottle: case report and narrative review of the literature.

INTRODUCTION: We described a case of alveolar hemorrhage (AH) after marijuana smoking using a water pipe made with plastic bottle (bong) before making a narrative review of the literature. CASE REPORT: A 19-year-old male was admitted for hemoptysis and dyspnea evolving since the previous day. He smoked marijuana ten times a day using bongs. Computed tomography scan of the chest (chest CT-scan) evidenced ground glass opacities involving upper lobes with crazy-paving pattern. Bronchoalveolar lavage (BAL) yielded fluid becoming progressively bloody suggestive of AH. Screening of drug metabolites ruled out the presence of cocaine degradation products. Treatment with prednisone was prescribed and oxygen requirements decreased rapidly. The patient accepted to stop bongs, but kept on smoking marijuana using joints. He was asymptomatic 2 months later; all ground glass opacities had vanished. REVIEW OF THE LITERATURE: Four cases described exactly the same circumstances as ours. All were young male patients containing ground glass opacities with diffuse or bilateral pattern in their chest CT-scan. The explanation suggested by the authors of these cases was the potential concomitant inhalation of acid anhydrides derived from use of heated plastic bottle. No acid anhydrides were experimentally evidenced after thermodesorption of heated polyethylene terephthalate (PET) (in which a majority of plastic bottles are made) we performed, but other compounds were. E-cigarette, or vaping, product use-associated lung injuries cases share some chest CT-scan patterns with those of AH following bong use and we tried to draw a parallel between these two latter before discussing a physiopathological hypothesis.

The antidiabetic drug glibenclamide exerts direct retinal neuroprotection.

Sulfonylureas, widely used as hypoglycemic agents in adults with type 2 diabetes, have neuroprotective effects in preclinical models of central nervous system injury, and in children with neuropsychomotor impairments linked to neonatal diabetes secondary to ATP-sensitive potassium channel mutations. In the human and rodent retina, we show that the glibenclamide-activated channel sulfonylurea receptor 1 (SUR1) is expressed in the retina and enriched in the macula; we also show that it colocalizes with the potassium channel Kir6.2, and with the cation channel transporter TRPM4. Glibenclamide (glyburide), administered at doses that did not decrease the glycemia, or injected directly into the eye, protected the structure and the function of the retina in various models of retinal injury that recapitulate the pathogenic neurodegenerative events in the diabetic retina. The downregulation of SUR1 using a siRNA suppressed the neuroprotective effects of glibenclamide on excitotoxic stress-induced cell death. The glibenclamide effects include the transcriptional regulation of antioxidant and neuroprotective genes. Ocular glibenclamide could be repurposed for diabetic retinopathy.

Quantification of methadone, buprenorphine, naloxone, opioids, and their derivates in whole blood by liquid chromatography-high-resolution mass spectrometry: Analysis of their involvement in fatal forensic cases.

Opioids represent a broad family of compounds that can be used in several indications: analgesics, antitussives, opioid substitution therapy (e.g. methadone, buprenorphine…). When these products are misused, they are often addictive. Thus, we aimed to develop an analytical method able to rapidly quantify several opiates and opioids (6-monoacetylmorphine, buprenorphine, codeine, dihydrocodeine, 2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolidine, ethylmorphine, heroin, methadone, morphine, nalbuphine, naloxone, norbuprenorphine, norcodeine, norpropoxyphene, oxycodone and propoxyphene) in whole blood by ultra-high performance liquid chromatography combined with high resolution mass spectrometry (UHPLC-HRMS). The validated assay requires only 100 µL of the blood sample. The sample is prepared by a rapid liquid-liquid extraction using 5% zinc sulfate (W/V), methanol and acetonitrile. Calibration curves range from 0.98 to 1000 µg/L, except for buprenorphine (0.39-100 µg/L) and norbuprenorphine (0.20-100 µg/L). Inter- and intra-analytical accuracy was less than 15%. Therefore, we describe the development and full validation of an accurate, sensitive and precise assay using UHPLC-HRMS for the analysis of opioids in whole blood. After validation, this new assay is successfully applied on a routine laboratory application basis.

Glibenclamide oral suspension: Suitable and effective in patients with neonatal diabetes.

BACKGROUND: Results of genetic have led to off-label glibenclamide treatment in patients with neonatal diabetes (NDM) because of potassium channel mutations. No pediatric form of glibenclamide was available. Glibenclamide was designated an orphan drug designation for NDM and a suspension was developed. As a part of the pediatric plan investigation, we assessed its acceptability, efficiency, and safety. METHODS: In this Phase II, prospective, non-randomized, single-center study, patient received glibenclamide tablets for 1 month then the suspension for 3 months. We assessed acceptability using hedonic scales and patient questionnaires, effectiveness using glycated hemoglobin (HbA1C) assays and safety based on hypo and hyperglycemia, and other adverse events. RESULTS: We included 10 patients (0.1-16.2 years, 6 < 5 years) were included. Younger patients preferred the suspension and older the tablets. All parents were satisfied with the ease of suspension administration. The parents of 5 of 6 younger children preferred the suspension over the tablets and kept it. Switching from tablets to suspension did not affect the excellent metabolic control (median HbA1c change, -0.40%, [-1.3% to 0.5%] P = 0.08). Median frequencies of hypoglycemia and hyperglycemia were less than 5% of routine blood glucose assays and were similar with both dosage forms. Two patients each experienced one episode of hypoglycemia below 35 mg/dL highlighting the need for dosage titration when switching from tablets to suspension. Transient and non-severe abdominal pain or diarrhea occurred in three patients. None of the patients discontinued the treatment. CONCLUSION: The glibenclamide oral suspension Amglidia, the first anti-diabetic drug specifically developed for pediatric patients, is acceptable, effective, and safe in patients with NDM (NCT02375828). CLINICAL TRIAL REGISTRATION: Glibentek in Patients with Neonatal Diabetes Secondary to Mutations in K + -ATP Channels, clinicaltrials.gov, NCT02375828, https://clinicaltrials.gov/ct2/show/NCT02375828.

Population pharmacokinetics of articaine with 1:200,000 epinephrine during third molar surgery and simulation of high-dose regimens.

BACKGROUND AND OBJECTIVES: Articaine is more and more used in third molar surgery under local anesthesia (LA). The objectives of this analysis were to characterize the pharmacokinetics of articaine for this type of surgery and to simulate dosing regimens. METHODS: Non-linear mixed-effects modeling conducted in Monolix 4.4.0 was used to describe articaine plasma concentration-time data from 20 patients. Monte Carlo simulations were then performed to evaluate the probability of cardiotoxic target attainment (PCTA) of various dosage regimens. RESULTS: Articaine concentration data were best described by a linear one-compartment model, with an additional depot compartment for submucosal route with a zero-order transfer to central compartment. Age and gender were found to influence duration transfer (Tk0) and elimination rate constant (Ke), respectively. Simulated maximum recommended dose regimen (7mg/kg) had a PCTA of 0%. Simulated higher doses of 10mg/kg and 15mg/kg had a PCTA of 0% and about 1-4%, respectively. CONCLUSIONS: The model adequately described the articaine pharmacokinetics. This is the first PK model qualified for articaine administered by submucosal route. The simulations suggest that maximum recommended dose regimen is safe concerning the cardiotoxicity in healthy patients.

Drowsiness and uncommon fever in a child after cannabis ingestion.

Trivialization of cannabis consumption goes hand in hand with a growing exposure of children and the number of cannabis poisoning cases is steadily increasing. As clinical presentation can be different from what is currently seen in adults, added to the fact that it is not always suspected, diagnosis of cannabis intoxication in children is often delayed or missed. A 16-month-old girl was admitted to the pediatric emergency unit for an important drowsiness combined to moderate fever. After elimination of infectious causes, a toxic origin was considered and biological analyses led to the diagnosis of involuntary acute cannabis intoxication. In conclusion, cannabis intoxication in child has uncommon presentations compared to that seen in adults. In this context, biological analyses have a great importance for a rapid diagnosis and also for the understanding intoxication circumstance. This is of paramount importance because it may lead to consider child protection measures.

Therapeutic drug monitoring of mitotane: Analytical assay and patient follow-up.

Adrenocortical carcinoma (ACC) is an aggressive malignancy of the adrenal gland. Mitotane (o,p'-DDD) is the most effective chemotherapy for ACC. According to the literature, mitotane plasma trough concentrations within 14-20 mg L-1 are correlated with a higher response rate with acceptable toxicity. Therapeutic drug monitoring (TDM) of mitotane is therefore recommended. The aim of this study was to propose a robust and simple method for mitotane quantification in plasma. The validation procedures were based on international guidelines. Sample preparation consisted of a single protein precipitation with methanol using 100 µL of plasma. The supernatant was submitted to liquid chromatography coupled with ultra-violet detection at 230 nm. Mitotane retention time was 7.1 min. The limit of detection was 0.1 mg L-1 and the limit of quantification was 0.78 mg L-1 . The assay demonstrated a linear range of 0.78-25 mg L-1 with correlation coefficients (r2 ) at 0.999. Inter- and intra-assay precision was <4.85%. Evaluation of accuracy showed a deviation <13.69% from target concentration at each quality control level. This method proved easy and rapid to perform mitotane TDM and required a small volume of sample. It was successfully applied to routine TDM in our laboratory.

A Slight Smell of Lemon.

We present here an example of urine substituted with a yellow cleaning product that leads us to develop the main risks to consider in urine toxicology analysis, ie, adulteration and analytical interferences, and how to deal with them. This grand round highlights the importance of the dialog between the clinician and a TDM consultant for optimal care of the patient.

False negative on a proven involuntary intoxication in two children with lorazepam.

Children aged between 1 to 4 years are the most at risk of unintentional poisonings. Benzodiazepines are the most medicine often cause of the poisoning. Among the twenty-two most prescribed benzodiazepines in France, lorazepam ranks fifth behind zolpidem, alprazolam, bromazepam and zopiclone. However the automated assay currently available does not allow to detect and/or to quantify lorazepam. The alternative to the immunoassay is the liquid chromatography coupled with mass spectrometry (HPLC/MS). This technique, highly sensitive and specific, requires a pre-treatment phase and a good technical proficiency, justifying specialized staff. The clinical cases presented here illustrate the major interest of availability to this type of technology in routine and 24h/24h.

Evaluation of the pharmacokinetics of glibenclamide tablet given, off label, orally to children suffering from neonatal syndromic hyperglycemia.

PURPOSE: Glibenclamide (Gb) is used in type II diabetes mellitus but also in the last 10 years, off label, in patients with neonatal syndromic hyperglycemia carrying a mutation of Kir6.2 or SUR1. No studies have reported Gb pharmacokinetics in children. In this study, oral Gb pharmacokinetics was investigated in children in order to describe the concentration time courses, the influence of covariates, and the relationships between drug concentrations and efficacy. METHODS: Gb concentrations were measured in 18 children after the switch from subcutaneous insulin to oral tablets of Gb (crushed tablets for 33 % of patients). A total of 229 plasma Gb concentrations and 187 blood glucose measurements were available. A population model was developed with NONMEM. RESULTS: Body weight was the most significant parameter on clearance and explained a substantial part of the variability. A variant genotype of CYP2C9 (i.e., *1/*2 and *1/*3) explained also a part of the remaining variability on Gb clearance. Patients carrying these allelic variants had a clearance decreased by 45 %. A link between daily area under the curve (AUC0-24 h) and metabolic control diabetes was found. CONCLUSIONS: This study evaluates for the first time the pharmacokinetics of oral Gb in children and constitutes a first step towards dose individualization of this drug in a particularly vulnerable population.