Transfer of cetirizine/levocetirizine into human breast milk and estimation of drug exposure to infants through breastfeeding: A human lactation study from the ConcePTION project

Data on drug transfer into human breast milk are sparse. This study aimed to quantify concentrations of cetirizine and levocetirizine in breast milk and to estimate drug exposure to infants. Breastfeeding women at least 8 weeks postpartum and using cetirizine or its pure (R)-enantiomer levocetirizine were eligible to participate. Breast milk samples were collected at six predefined times during a dose interval (0, 2, 4, 8, 12 and 24 h after drug intake) at steady state. Infant drug exposure was estimated by calculating the absolute infant dose (AID) and the weight-adjusted relative infant dose (RID). In total, 32 women were eligible for final inclusion, 31 women using cetirizine and one woman using levocetirizine. Means of the individual maximum and average cetirizine milk concentrations were 41.0 and 16.8 μg/L, respectively. Maximum concentrations occurred on average 2.4 h after intake, and the mean half-life in milk was 7.0 h. Estimated AID and RID for cetirizine in a day were 2.5 μg/kg and 1.9%, respectively. The corresponding values for levocetirizine were 1.1 μg/kg and 1.9%. No severe adverse events were reported. Our findings demonstrate that the transfer of cetirizine and levocetirizine into breast milk is low and compatible with breastfeeding.

Multivariate Exact Discrepancy: A New Tool for PK/PD Model Evaluation

BACKGROUND

Pharmacokinetic models are evaluated using three types of metrics: those based on estimating the typical pharmacokinetic parameters, those based on predicting individual pharmacokinetic parameters and those that compare data and model distributions. In the third groups of metrics, the best-known methods are Visual Predictive Check (VPC) and Normalised Prediction Distribution Error (NPDE). Despite their usefulness, these methods have some limitations, especially for the analysis of dependent concentrations, i.e., evaluated in the same patient.

OBJECTIVE

In this work, we propose an evaluation method that accounts for the dependency between concentrations.

METHODS

Thanks to the study of the distribution of simulated vectors of concentrations, the method provides one probability per individual that its observations (i.e., concentrations) come from the studied model. The higher the probability, the better the model fits the individual. By examining the distribution of these probabilities for a set of individuals, we can evaluate the model as a whole.

RESULTS

We demonstrate the effectiveness of our method through two examples. Our approach successfully detects misspecification in the structural model and identifies outlier kinetics in a set of kinetics.

CONCLUSION

We propose a straightforward method for evaluating models during their development and selecting a model to perform therapeutic drug monitoring. Based on our preliminary results, the method is very promising but needs to be validated on a larger scale.

[Risk assessment of drugs during breastfeeding]

Medication intake during the postpartum period is common with discontinuation of breastfeeding sometimes unnecessarily recommended for fear of adverse effects in the breastfed infant, while exposure through human milk is generally low. The assessment of risks associated with medication intake during breastfeeding is based, among other things, on the little clinical evidence available in specialized sources of information, and on pharmacokinetic principles. A decision-making support is presented to facilitate communication with mothers, foster medication adherence and prevent unnecessary interruption of breastfeeding.

Exploration of the relationship between cumulative exposure to tobramycin and ototoxicity in patients with cystic fibrosis

BACKGROUND

Aminoglycosides (AGs), such as tobramycin, are essential antibiotics in the management of pulmonary infections in patients with cystic fibrosis (CF). They induce ototoxicity without the relationship being clearly described in the literature. Our aim is to propose a mathematical and statistical model describing the relationship between the estimated cumulative exposure (Area Under the Curve, AUC) to tobramycin and ototoxicity with audiogram interpretation in young patients with CF.

METHODS

Cumulative AUCs were estimated for each course of tobramycin, for the 106 individuals with CF (between 4 and 22 years of age) enrolled in this retrospective study (35 who had received IV tobramycin, 71 controls). Mean hearing loss was calculated for each audiogram and a statistical model was developed to predict hearing loss.

RESULTS

The model confirms a significant relationship between cumulative tobramycin exposure and changes in hearing acuity: Meanhearingloss=2.7+(3×10-5)×AUC_tobramycin+individual_susceptibility However, the ototoxic effect is not clinically perceptible (mean hearing loss: 3.8 dB). The impact of AUC on hearing loss is minor in these subjects who received a limited number of courses of tobramycin (median: 5 courses).

CONCLUSION

A significant relationship between cumulative exposure to tobramycin and ototoxicity was demonstrated. Individual treatment susceptibility should not be overlooked. As ototoxicity is not clinically perceptible in the study subjects, hearing tests should be continued during adulthood to provide individualized medical guidance and to obtain a lifetime analysis of the relationship between exposure and hearing loss.

Safety of medicines during breastfeeding - from case report to modeling : A contribution from the ConcePTION project

INTRODUCTION

Despite many research efforts, current data on the safety of medicines during breastfeeding are either fragmented or lacking, resulting in restrictive labeling of most medicines. In the absence of pharmacoepidemiologic safety studies, risk estimation for breastfed infants is mainly derived from pharmacokinetic (PK) information on the medicine. This manuscript provides a description and a comparison of the different methodological approaches that can yield reliable information on medicine transfer into human milk and the resulting infant exposure.

AREA COVERED

Currently, most information on medicine transfer in human milk relies on case reports or traditional PK studies, which generate data that can hardly be generalized to the population. Some methodological approaches, such as population PK (popPK) and physiologically-based PK (PBPK) modeling, can be used to provide a more complete characterization of infant medicine exposure through human milk and simulate the most extreme situations, while decreasing the burden of sampling in breastfeeding women.

EXPERT OPINION

PBPK and popPK modeling are promising approaches to fill the gap of knowledge in medicine safety in breastfeeding, as illustrated with our escitalopram example.

Infant exposure to Fluvoxamine through placenta and human milk: a case series - A contribution from the ConcePTION project

Introduction

Fluvoxamine is widely used to treat depression during pregnancy and lactation. However, limited data are available on its transfer to the fetus or in human milk. This case series provides additional information on the infant exposure to fluvoxamine during pregnancy and lactation.

Case presentation

Two women, aged 38 and 34 years, diagnosed with depression were treated with 50 mg fluvoxamine during pregnancy and lactation. At delivery a paired maternal and cord blood sample was collected for each woman. The first mother exclusively breastfed her child for 4 months and gave one foremilk and one hindmilk sample at 2 days and 4 weeks post-partum, whereas the second mother did not breastfeed.

Results

The cord to plasma concentration ratios were 0.62 and 0.48, respectively. At 2 weeks post-partum, relative infant doses (RID) were 0.47 and 0.57% based on fluvoxamine concentrations in foremilk and hindmilk, respectively. At 4 weeks post-partum, the RIDs were 0.35 and 0.90%, respectively. The child from the first mother was born healthy and showed a normal development at the 6th, 18th and 36th month follow-ups. One of the twins from the second woman was hospitalized for hypoglycemia that was attributed to gestational diabetes and low birth weight. The second one was born healthy.

Conclusion

These results suggest a minimal exposure to fluvoxamine during lactation which is in accordance with previously published data. Larger clinical and pharmacokinetic studies assessing the long-term safety of this drug during lactation and the variability of its exposure through breastmilk are warranted.

Optimization of ICP-MS internal standardization for 26 elements by factorial design experiment

INTRODUCTION

Internal standardization is a common tool used in inductively coupled plasma - mass spectrometry (ICP-MS) analysis in order to reduce matrix effects, and thus improve the reliability and the robustness of results. However, its efficacy relies on the choice of a proper internal standard (IS) which, ideally, undergoes the same signal variations as the analyte. Thus far, IS selection has mainly relied on the proximity of atomic mass between the analyte and the internal standard. However, while it may be a satisfactory rule of thumb, more recent works suggest that this criterium might not be suitable in several conditions, among which the presence of high amounts of carbon atoms in the sample. This may thus be of particular interest in the case of trace elements determination in biological samples.

MATERIALS AND METHODS

In this study, we propose an empirical and global approach to IS selection in ICP-MS through the use of a factorial design of experiments (DoE), with a focus on biological matrices of interest in clinical analysis: human blood and urine. The suitability of 13 potential IS was evaluated for 26 clinically-relevant analytes, including a polyatomic ion obtained through reaction with oxygen, across 324 experimental conditions.

RESULTS AND DISCUSSION

The results underline several exceptions to the rule of IS selection based on mass proximity, notably when considering heavy or polyatomic analytes. As a consequence, measurements of said analytes in several extreme experimental conditions using IS selected by mass proximity could yield vastly erroneous results (up to 30 times the theoretical concentrations). By contrast, the use of empirically selected IS yielded much more acceptable results.

Biased computation of probability of target attainment for antimicrobial drugs

The medical literature is replete with articles in which there is confusion between "free concentration" and "unbound fraction" (f_u ), which is the ratio of free to total plasma concentration. The lack of clarity in distinguishing between these two terms has led to biased computations, erroneous interpretations, and misleading recommendations. The problems are highlighted in this paper, taking the example of calculation of Probability of Target Attainment (PTA). This metric is used to propose pharmacokinetic/pharmacodynamic (PK/PD) breakpoints required for the interpretation of Antimicrobial Susceptibility Testing. Based on Monte Carlo simulations of the PK/PD index, area under the unbound concentration time curve/minimum inhibitory concentration (fAUC/MIC), computation of PTA from total plasma concentrations scaled by f_u ineluctably leads to biased estimates. The bias is greater if the variability associated with f_u is added, instead of removing it during this scaling. The explanation for the bias is that total plasma drug concentrations are intrinsically more variable than the corresponding free concentrations. This is due to the variability of antimicrobial binding for total, but not for free plasma concentrations. In consequence, the greater variability always leads to underestimation of the PK/PD cutoff (i.e., the critical MIC that is guaranteed for a given percentile of the population). A further consequence is an increase in calculated dosage required to attain the targeted quantile. This erroneous approach, of using free antimicrobial drug fraction, is not limited to the derivation of PK/PD cutoff, but may also have consequences for antimicrobials drug safety in clinical patients.

Maternal drugs and breastfeeding: Risk assessment from pharmacokinetics to safety evidence - A contribution from the ConcePTION project

Human milk is the most appropriate form of nutrition for infants while taking medication during the postpartum period is common. Discontinuation of breastfeeding is sometimes wrongly recommended for fear of adverse effects in the breastfed infant whereas only a few drugs are strictly contraindicated while breastfeeding. Most drugs are transferred from the mother's blood to the milk, but the breastfed infant usually ingests a small drug amount through human milk. As population-based evidence is still scarce on safety of drugs during breastfeeding, risk assessment relies on the little clinical evidence available and on pharmacokinetic principles, as well as on specialized sources of information that are essential for clinical decision-making. Risk assessment should not only be based on the drug's potential risk for the breastfed infant but should always take into account the benefits associated to breastfeeding, the risks of untreated maternal disease and the maternal willingness to breastfeed. Identifying situations with potential for drug accumulation in the breastfed infant is decisive while assessing the risk. Health care providers should always assume that mothers will be concerned and use risk communication as a key to ensure medication adherence and prevent unnecessary interruption of breastfeeding. When a mother still expresses concerns, decision support algorithms may facilitate communication and some strategies can be offered to minimize the drug exposure in the breastfed infant even when clinically not justified.

Method validation and clinical application for the quantification of lopinavir, efavirenz, and ritonavir in breast milk using liquid chromatography tandem mass spectrometry

A liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been validated for quantification of three antiretroviral drugs (efavirenz [EFV], lopinavir [LPV], and ritonavir [RTV]) from human breast milk. The samples were extracted employing protein precipitation method using methanol as precipitating agent. The supernatant was evaporated and reconstituted before injecting into the chromatograph and separated on a biphenyl column. Calibration curves for the three tested antiretroviral drugs were linear (r ≥ 0.999) over the range examined. The inter- and intra-day coefficients of variation (CV) were ≤15% for efavirenz, lopinavir, and ritonavir. Mean recovery ranged from 96% to 105% and no major matrix effects were observed. This validated LC-MS/MS method was efficiently applied to determine EFV, LPV, and RTV concentrations in breast milk from Human Immunodeficiency Virus (HIV)-positive breastfeeding mothers. This assay requires a simple sample processing method with a short run time, making it well suited for high-throughput routine clinical or research purposes.

Evaluation of 4 quantification methods for monitoring 16 antibiotics and 1 beta-lactamase inhibitor in human serum by high-performance liquid chromatography with tandem mass spectrometry detection

Antibiotic (ATB) prescription in an intensive care unit (ICU) requires continuous monitoring of serum dosages due to the patient's pathophysiological condition. Dosing adjustment is necessary to achieve effective targeted concentrations. Since ICUs routinely use a large number of ATBs, global monitoring needs to be developed. In the present study, we developed a global analytical method for extracting, separating and quantifying the most widely used ATBs in ICUs: amoxicillin, piperacillin, cefazolin, cefepime, cefotaxime, ceftazidime, ceftolozane, ceftriaxone, ertapenem, meropenem, ciprofloxacin, moxifloxacin, levofloxacin, daptomycin, dalbavancin, linezolid and a beta-lactamase inhibitor: tazobactam. To guarantee the robustness of the quantification, we differentiated the 16 ATBs and the beta lactamase inhibitor into 4 pools (ATB1 to ATB4), taking into account prescription frequency in the ICU, the physicochemical properties and the calibration ranges of the ATBs selected. The whole ATB was then separated with two LC columns in reversed phase: Kinetex Polar-C18 100 Å and Polar-RP-80 synergy, in less than 6.5 min. Detection was carried out by electrospray in positive ion mode, by tandem mass spectrometry (LC-MS/MS. The four quantification methods were validated according to the European guidelines on bioanalytical method validation (EMEA guide), after determining the extraction yields, matrix effects, recovery, precision, accuracy, within-run precision and between-run precision. For all analyses, bias is < 15% and is comparable to the literature and LOQs vary from 0.05 mg.L^-1 for ciprofloxacin to 1.00 mg.L^-1 for ceftriaxone and dalbavancin. The stability time of cefepime and piperacillin is 3 hrs and for the other ATBs 6 hrs in serum at room temperature. For long-term stability, freezing at - 80 °C guarantees 3 months of stability for ceftriaxone and dalbavancin and more than 6 months for the other ATBs.

"De-Shrinking" EBEs: The Solution for Bayesian Therapeutic Drug Monitoring

BACKGROUND

Therapeutic drug monitoring (TDM) aims at individualising a dosage regimen and is increasingly being performed by estimating individual pharmacokinetic parameters via empirical Bayes estimates (EBEs). However, EBEs suffer from shrinkage that makes them biased. This bias is a weakness for TDM and probably a barrier to the acceptance of drug dosage adjustments by prescribers.

OBJECTIVE

The aim of this article is to propose a methodology that allows a correction of EBE shrinkage and an improvement in their precision.

METHODS

As EBEs are defined, they can be seen as a special case of ridge estimators depending on a parameter usually denoted λ. After a bias correction depending on λ, we chose λ so that the individual pharmacokinetic estimations have minimal imprecision. Our estimate is by construction always better than EBE with respect to bias (i.e. shrinkage) and precision.

RESULTS

We illustrate the performance of this approach with two different drugs: iohexol and isavuconazole. Depending on the patient's actual pharmacokinetic parameter values, the improvement given by our approach ranged from 0 to 100%.

CONCLUSION

This innovative methodology is promising since, to the best of our knowledge, no other individual shrinkage correction has been proposed.

Tacrolimus Intrapatient Variability After Switching From Immediate or Prolonged-Release to Extended-Release Formulation, After an Organ Transplantation

Background and Purpose: Several formulations of tacrolimus are available, but evidence of the benefit of changing to the most recent formulations is lacking. Tacrolimus intra-patient variability (tacrolimus IPV) is an emerging risk factor associated with poor graft outcomes after solid organ transplantations. Here, we examined the modifications of tacrolimus IPV after switching to a different formulation of tacrolimus. Experimental Approach: We identified 353 solid organ transplant recipients that were switched in our center from immediate-release (IR-tacrolimus) or prolonged-release tacrolimus (PR-tacrolimus) to extended-release, LCP-tacrolimus (LCP-tacrolimus). Among them, 54 patients underwent at least 3 available tacrolimus blood concentrations before and after the switch, allowing us to investigate tacrolimus IPV. Key Results: The switch was considered as a safe procedure since only four of the 353 patients presented a graft rejection after the switch, and no patient was hospitalized for tacrolimus overdose. The tacrolimus IPV estimated by the coefficient of variation (CV-IPV) was stable before and after the switch to LCP-tacrolimus (CV-IPV: 29.0% (IQR 25-75 (15.5; 38.5) before and 24.0% (15.8; 36.5) after the switch, p = 0.65). Conclusion and Implications: Switching from IR- or PR-tacrolimus to LCP-tacrolimus is a safe procedure. However, the CV-tacrolimus IPV was not impacted by the change of formulation.

Efficacy of dihydroartemisinin/piperaquine in patients with non-complicated Plasmodium falciparum malaria in Yaoundé, Cameroon

BACKGROUND

Dihydroartemisinin/piperaquine is increasingly used for the treatment of uncomplicated Plasmodium falciparum malaria in Africa. The efficacy of this combination in Cameroon is poorly documented, while resistance to dihydroartemisinin/piperaquine readily spreads in Southeast Asia.

OBJECTIVES

This study evaluated the clinical efficacy of dihydroartemisinin/piperaquine in Cameroon, as well as the molecular profile and phenotypic susceptibility of collected isolates to dihydroartemisinin and piperaquine.

PATIENTS AND METHODS

Dihydroartemisinin/piperaquine efficacy in 42 days was followed-up for 138 patients presenting non-complicated falciparum malaria. Piperaquine concentration was determined at day 7 for 124 patients. kelch13 gene polymorphisms (n = 150) and plasmepsin2 gene amplification (n = 148) were determined as molecular markers of resistance to dihydroartemisinin and piperaquine, respectively. Parasite susceptibility to dihydroartemisinin and piperaquine was determined using validated in vitro survival assays.

RESULTS

The efficacy of dihydroartemisinin/piperaquine treatment was 100% after PCR correction. The reinfections were not associated with a variation of piperaquine concentration at day 7. Ninety-six percent (144/150) of the samples presented a WT allele of the kelch13 gene. Two percent (3/150) presented the non-synonymous mutation A578S, which is not associated with resistance to dihydroartemisinin. No duplication of the plasmepsin2 gene was observed (0/148). All the samples tested in vitro by survival assays (n = 87) were susceptible to dihydroartemisinin and piperaquine.

CONCLUSIONS

Dihydroartemisinin/piperaquine has demonstrated excellent therapeutic efficacy with no evidence of emerging artemisinin or piperaquine resistance in Yaoundé, Cameroon. This observation suggests that dihydroartemisinin/piperaquine could be a sustainable therapeutic solution for P. falciparum malaria if implemented in areas previously free of artemisinin- and piperaquine-resistant parasites, unlike Southeast Asia.

Neglecting Plasma Protein Binding in COVID-19 Patients Leads to a Wrong Interpretation of Lopinavir Overexposure

Boffito et al. recalled the critical importance to correctly interpret protein binding. Changes of lopinavir pharmacokinetics in coronavirus disease 2019 (COVID‐19) are a perfect illustration. Indeed, several studies described that total lopinavir plasma concentrations were considerably higher in patients with severe COVID‐19 than those reported in patients with HIV. These findings have led to a reduction of the dose of lopinavir in some patients, hypothesizing an inhibitory effect of inflammation on lopinavir metabolism. Unfortunately, changes in plasma protein binding were never investigated. We performed a retrospective cohort study. Data were collected from the medical records of patients hospitalized for COVID‐19 treated with lopinavir/ritonavir in intensive care units or infectious disease departments of Toulouse University Hospital (France). Total and unbound concentrations of lopinavir, C reactive protein, albumin, and alpha‐1‐acid glycoprotein (AAG) levels were measured during routine care on the same samples. In patients with COVID‐19, increased total lopinavir concentration is the result of an increased AAG‐bound lopinavir concentration, whereas the unbound concentration remains constant, and insufficient to reduce the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) viral load. Although international guidelines have recently recommended against using lopinavir/ritonavir to treat severe COVID‐19, the description of lopinavir pharmacokinetics changes in COVID‐19 is a textbook case of the high risk of misinterpretation of a total drug exposure when changes in protein binding are not taken into consideration.

Determining the therapeutic range for ribavirin in transplant recipients with chronic hepatitis E virus infection

The aim of this study was to define the therapeutic range for ribavirin (RBV) in transplant recipients with chronic hepatitis E virus (HEV) infection. In this retrospective multicentre cohort study, data of adult transplant recipients with chronic HEV infection, who had been treated with RBV monotherapy between 01-3-2008 and 01-08-2018, were included. ROC curve analyses were performed, and the half-maximal effective RBV concentration was calculated to determine a representative therapeutic range. In 96 patients, RBV monotherapy for a median of three months resulted in a sustained virologic response in 63.5% of the patients, while 88.5% of the patients developed anaemia. RBV plasma concentrations at steady state were significantly higher in clinical responders compared with clinical non-responders: median 1.96 (IQR 1.81-2.70) versus 0.49 (IQR 0.45-0.73) mg/L, P = .0004. RBV caused a dose-dependent haemoglobin reduction with higher RBV plasma concentrations resulting in more haemoglobin reduction. The therapeutic range for RBV for chronic HEV infection in transplant recipients ranges between 1.8 and 2.3 mg/L.

A comprehensive review on non-clinical methods to study transfer of medication into breast milk - A contribution from the ConcePTION project

Breastfeeding plays a major role in the health and wellbeing of mother and infant. However, information on the safety of maternal medication during breastfeeding is lacking for most medications. This leads to discontinuation of either breastfeeding or maternal therapy, although many medications are likely to be safe. Since human lactation studies are costly and challenging, validated non-clinical methods would offer an attractive alternative. This review gives an extensive overview of the non-clinical methods (in vitro, in vivo and in silico) to study the transfer of maternal medication into the human breast milk, and subsequent neonatal systemic exposure. Several in vitro models are available, but model characterization, including quantitative medication transport data across the in vitro blood-milk barrier, remains rather limited. Furthermore, animal in vivo models have been used successfully in the past. However, these models don't always mimic human physiology due to species-specific differences. Several efforts have been made to predict medication transfer into the milk based on physicochemical characteristics. However, the role of transporter proteins and several physiological factors (e.g., variable milk lipid content) are not accounted for by these methods. Physiologically-based pharmacokinetic (PBPK) modelling offers a mechanism-oriented strategy with bio-relevance. Recently, lactation PBPK models have been reported for some medications, showing at least the feasibility and value of PBPK modelling to predict transfer of medication into the human milk. However, reliable data as input for PBPK models is often missing. The iterative development of in vitro, animal in vivo and PBPK modelling methods seems to be a promising approach. Human in vitro models will deliver essential data on the transepithelial transport of medication, whereas the combination of animal in vitro and in vivo methods will deliver information to establish accurate in vitro/in vivo extrapolation (IVIVE) algorithms and mechanistic insights. Such a non-clinical platform will be developed and thoroughly evaluated by the Innovative Medicines Initiative ConcePTION.

Hydroxychloroquine in Coronavirus Disease 2019 Patients: What Still Needs to Be Known About the Kinetics

Different dosage regimens of hydroxychloroquine are used to manage COVID-19 patients, without information on the pharmacokinetics in this population.Blood samples (n=101) were collected from 57 COVID-19 patients for 7 days and concentrations were compared with simulated kinetic profiles.Hydroxychloroquine exposure is low and cannot be predicted by other populations.

Hydroxychloroquine lung pharmacokinetics in critically ill patients with COVID-19

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HCQ pharmacokinetics in COVID-19 patients cannot be predicted using data from lupus or rheumatoid arthritis patients.

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Bronchoalveolar lavage fluid may be a more instructive matrix than plasma on the degree of HCQ lung exposure.

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Low plasma concentrations should not induce an increase in drug dosage because lung exposure could already be high.

Different dosage regimens of hydroxychloroquine (HCQ) have been used to manage COVID-19 (coronavirus disease 2019) patients, with no information on lung exposure in this population. The aim of our study was to evaluate HCQ concentrations in the lung epithelial lining fluid (ELF) in patients infected with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the virus that causes COVID-19. This was a retrospective, observational, multicentre, pharmacokinetic study of HCQ in critically ill COVID-19 patients. No additional interventions or additional samples compared with standard care of these patients were conducted in our teaching hospital. We included all intubated COVID-19 patients treated with crushed HCQ tablets, regardless of the dosage administered by nasogastric tube. Blood and bronchoalveolar lavage samples (n = 28) were collected from 22 COVID-19 patients and total HCQ concentrations in ELF were estimated. Median (interquartile range) HCQ plasma concentrations were 0.09 (0.06–0.14) mg/L and 0.07 (0.05–0.08) mg/L for 400 mg × 1/day and 200 mg × 3/day, respectively. Median HCQ ELF concentrations were 3.74 (1.10–7.26) mg/L and 1.81 (1.20–7.25) for 400 mg × 1/day and 200 mg × 3/day, respectively. The median ratio of ELF/plasma concentrations was 40.0 (7.3–162.7) and 21.2 (18.4–109.5) for 400 mg × 1/day and 200 mg × 3/day, respectively. ELF exposure is likely to be underestimated from HCQ concentrations in plasma. In clinical practice, low plasma concentrations should not induce an increase in drug dosage because lung exposure may already be high.

Safety of Pyrazinamide for the Treatment of Tuberculosis in Older Patients Over 75 Years of Age: A Retrospective Monocentric Cohort Study

OBJECTIVES

Pyrazinamide (PZA) has a controversial safety profile in older patients. We aimed to assess the frequency and risk factors for adverse drug reactions (ADRs) in patients over 75 years of age treated for tuberculosis with or without PZA.

METHODS

We conducted a retrospective monocentric study including patients aged over 75 years treated for active tuberculosis between 2008 and 2018. The frequency, type, seriousness, and causality assessment of ADRs to anti-tuberculosis treatment were compared between patients receiving PZA or not. Risk factors for ADRs were investigated using univariable and multivariable analyses by logistic regression.

RESULTS

Among the 110 patients included, 54 (49.1%) received PZA (group 1) and 56 (50.9%) did not (group 2). ADRs to anti-tuberculosis drugs occurred in 31 patients (57.4%) in groups 1 and 15 (26.8%) in group 2 (p = 0.003). PZA-related ADRs occurred in 40.7% of exposed patients. Frequency of renal ADRs was higher in group 1 (9.3% vs 0%; p = 0.026). Rates of hepatic (18.5% vs 12.5%; p = 0.38), digestive (22.2% vs 8.9%; p = 0.054), and allergic (14.8% vs 5.4%; p = 0.12) ADRs were numerically higher in group 1 although the differences were not statistically significant. Serious ADRs occurred more frequently in group 1 (24.1% vs 8.9%; p = 0.03). The use of PZA was the only independent risk factor for ADRs to anti-tuberculosis drugs (odds ratio 3.75, 95% CI 1.5-9.6; p = 0.0056). No risk factors for PZA-related ADRs were identified.

CONCLUSION

In older French patients, the use of PZA was associated with more frequent ADRs to anti-tuberculosis drugs.

Levothyrox® New and Old Formulations: Are they Switchable for Millions of Patients?

In France, more than 2.5 million patients are currently treated with levothyroxine, mainly as the marketed product Levothyrox^®. In March 2017, at the request of French authorities, a new formulation of Levothyrox^® was licensed, with the objective of avoiding stability deficiencies of the old formulation. Before launching this new formulation, an average bioequivalence trial, based on European Union recommended guidelines, was performed. The implicit rationale was the assumption that the two products, being bioequivalent, would also be switchable, allowing substitution of the new for the old formulation, thus avoiding the need for individual calibration of the dosage regimen of thyroxine, using the thyroid-stimulating hormone level as the endpoint, as required for a new patient on initiating treatment. Despite the fact that both formulations were shown to be bioequivalent, adverse drug reactions were reported in several thousands of patients after taking the new formulation. In this opinion paper, we report that more than 50% of healthy volunteers enrolled in a successful regulatory average bioequivalence trial were actually outside the a priori bioequivalence range. Therefore, we question the ability of an average bioequivalence trial to guarantee the switchability within patients of the new and old levothyroxine formulations. We further propose an analysis of this problem using the conceptual framework of individual bioequivalence. This involves investigating the bioavailability of the two formulations within a subject, by comparing not only the population means (as established by average bioequivalence) but also by assessing two variance terms, namely the within-subject variance and the variance estimating subject-by-formulation interaction. A higher within individual variability for the new formulation would lead to reconsideration of the appropriateness of the new formulation. Alternatively, a possible subject-by-formulation interaction would allow a judgement on the ability, or not, of doctors to manage patients effectively during transition from the old to the new formulation.

Comparing ultrafiltration and equilibrium dialysis to measure unbound plasma dolutegravir concentrations based on a design of experiment approach

Dolutegravir therapeutic drug monitoring (TDM) could be improved by measuring the unbound dolutegravir plasma concentration (Cu), particularly in patients experiencing virological failure or toxicity despite achieving appropriate DTG total plasma concentrations. Equilibrium dialysis (ED) is the gold standard to measure Cu, but ED is time consuming, precluding its use in clinical practice. In contrast, ultrafiltration is applicable to TDM, but is sensitive to numerous analytical conditions. In order to evaluate measurements of Cu by ultrafiltration, ultrafiltration conditions were validated by comparison with ED. DTG concentrations were measured by LC–MS/MS. Three ultrafiltration factors (temperature, duration and relative centrifugal force [RCF]) were evaluated and compared to ED (25/37 °C), using a design of experiment strategy. Temperature was found to influence Cu results by ED (p = 0.036) and UF (p = 0.002) when results were analysed with ANOVA. Relative centrifugal force (2000 g) and time (20 min) interacted to influence Cu (p = 0.006), while individually they did not influence Cu (p = 0.88 and p = 0.42 for RCF and time). Ultrafiltration conditions which yielded the most comparable results to ED were 37 °C, 1000 g for 20 min. Ultrafiltration results greatly depended on analytical conditions, confirming the need to validate the method by comparison with ED in order to correctly interpret DTG Cu.

Influence of extracorporeal membrane oxygenation on the pharmacokinetics of ceftolozane/tazobactam: an ex vivo and in vivo study

Background

Extracorporeal membrane oxygenation (ECMO) is increasingly used in intensive care units and can modify drug pharmacokinetics and lead to under-exposure associated with treatment failure. Ceftolozane/tazobactam is an antibiotic combination used for complicated infections in critically ill patients. Launched in 2015, sparse data are available on the influence of ECMO on the pharmacokinetics of ceftolozane/tazobactam. The aim of the present study was to determine the influence of ECMO on the pharmacokinetics of ceftolozane-tazobactam.

Methods

An ex vivo model (closed-loop ECMO circuits primed with human whole blood) was used to study adsorption during 8-h inter-dose intervals over a 24-h period (for all three ceftolozane/tazobactam injections) with eight samples per inter-dose interval. Two different dosages of ceftolozane/tazobactam injection were studied and a control (whole blood spiked with ceftolozane/tazobactam in a glass tube) was performed. An in vivo porcine model was developed with a 1-h infusion of ceftolozane–tazobactam and concentration monitoring for 11 h. Pigs undergoing ECMO were compared with a control group. Pharmacokinetic analysis of in vivo data (non-compartmental analysis and non-linear mixed effects modelling) was performed to determine the influence of ECMO.

Results

With the ex vivo model, variations in concentration ranged from − 5.73 to 1.26% and from − 12.95 to − 2.89% respectively for ceftolozane (concentrations ranging from 20 to 180 mg/l) and tazobactam (concentrations ranging from 10 to 75 mg/l) after 8 h. In vivo pharmacokinetic exploration showed that ECMO induces a significant decrease of 37% for tazobactam clearance without significant modification in the pharmacokinetics of ceftolozane, probably due to a small cohort size.

Conclusions

Considering that the influence of ECMO on the pharmacokinetics of ceftolozane/tazobactam is not clinically significant, normal ceftolozane and tazobactam dosing in critically ill patients should be effective for patients undergoing ECMO.

Suicide Attempts: How Does the Acute Use of Alcohol Affect Suicide Intent?

BACKGROUND

Very few studies have specifically addressed the role of the acute use of alcohol (AUA) in suicide attempts.

OBJECTIVE

Our study compared the suicide intent scores of self-poisoning patients with and without AUA in order to examine the role of alcohol in attempted suicides.

METHODS

We recruited 516 patients admitted to the emergency department for self-poisoning. We screened blood alcohol concentrations (BACs) to determine whether these were positive or negative in the two groups. We collected data about covariates such as psychiatric disorders and sociodemographic and suicide characteristics. We then compared suicide intent between the groups, adjusted according to the covariates.

RESULTS

The patients with AUA had lower scores for suicide intent, but this factor only reduced the self-reporting score, with the scores for objective circumstances and risk similar between the groups. There was a correlation between BACs and self-reported suicide intentionality, but this was not significant.

CONCLUSION

Acute use of alcohol patients presented with lower suicide intent, as particularly explained by the self-report scores, but there were no differences between the groups in terms of risk and/or the objective circumstances. The role of alcohol in the self-reporting of suicide attempts must be addressed in future studies.

[Assessment for antihypertensive drug intake in France in 2019 and adherence]

Non-adherence to antihypertensive treatment is one of the critical contributors to sub-optimal blood pressure control. The French Society of Hypertension remembered that urine and serum biochemical detection of antihypertensive drugs could be useful in a patient with resistant hypertension. Talking to a patient with biochemically confirmed non-adherence to blood pressure-lowering therapy and repeating them improved adherence to drugs. Despite its usefulness, biochemical detection of antihypertensive drugs is not routinely effective in France as they are not reimbursed by French Medical Care, except in patients attending hospitals. The list of blood pressure-lowering drugs able to be biochemically detected in France and their modalities are recorded here.

Memory impairment following intentional self-poisoning with benzodiazepines: Should we pay more attention to attention?

STUDY HYPOTHESIS

In cases where patients attempt suicide through intentional self-poisoning, they often ingest drugs such as benzodiazepines that alter the central nervous system and memory. This is problematic, given that experts recommend the recovery of a patient's cognitive capacity before any psychiatric assessment is conducted. A previous pilot study by our group showed that cognitive tests focusing on attention are the most valuable when it comes to determining whether sufficient cognitive recovery has occurred to ensure that patients will remember the assessment after intentional self-poisoning with benzodiazepines. The main aim of our study was to determine cognitive predictors of the recall of the psychiatric assessment after a suicide attempt. The second aim was to determine the threshold for episodic memory.

METHODS

We recruited 97 patients admitted for intentional self-poisoning. At the time of the psychiatric assessments, we quantified plasma benzodiazepine levels and performed a cognitive assessment. We then used a linear regression model to identify the associations in a control and a benzodiazepine group between cognitive functions and episodic memory scores obtained 24 hours after psychiatric assessment.

RESULTS

Our model accounted for 28% and 37%, respectively, of the variance in memory in the control and benzodiazepine groups. The most significant correlations were found for the Wechsler Adult Intelligence Scale coding test in both groups. In the control group, tests such as visual and verbal memory were also associated with recall.

CONCLUSIONS

Benzodiazepines particularly affect memory by impairing what is remembered of attentional tests. These are, however, the most suitable cognitive tests for predicting recall of the memory assessment.

Refining the therapeutic range of posaconazole and isavuconazole for efficient therapeutic drug monitoring using a bioassay approach

Therapeutic drug monitoring (TDM) of antifungal triazole was recommended, except for isavuconazole (ISA) whose target trough concentrations (C_min ) need to be specified. Concerning posaconazole (POS), tablet formulation results in higher exposure but no upper C_min threshold has been yet proposed. We aimed to investigate the pharmacokinetic-pharmacodynamic relationship of POS and ISA, using a bioassay approach as surrogate marker of antifungal activity, in order to refine the therapeutic C_min of both antifungals. A bioassay using a cellulose disk diffusion method was performed to determine the growth inhibition zone (GIZ) of POS and ISA on Aspergillus fumigatus and Candida parapsilosis (ISA only). GIZs of plasma from patients undergoing TDM for POS (n = 136) or ISA (n = 40) were determined. GIZs of plasma patients and antifungal C_min were highly correlated for ISA (A. fumigatus: ρ = 0.942, P < 0.0001; C. parapsilosis: ρ = 0.949, P < 0.0001) and POS (ρ = 0.922, P < 0.0001), and these relationships were represented with a Michaelis-Menten model. Based on this modeling, the recommended thresholds of 0.7, 1, and 1.25 mg/L for the POS C_min corresponded to 50.1, 55.2, and 59.1% of the maximal GIZ, respectively. We propose an upper threshold of 4.8 mg/L for the POS C_min and a lower threshold of 2.0 mg/L for the C_min of ISA, as they respectively corresponded to concentrations leading to 90% and 50% of the maximal GIZ on A. fumigatus. The determination of antifungal activity using this bioassay allowed refining target C_min of POS and ISA, especially the upper threshold of POS (4.8 mg/L) and the lower threshold of ISA (2.0 mg/L).

Optimization of the treatment with beta-lactam antibiotics in critically ill patients-guidelines from the French Society of Pharmacology and Therapeutics (Société Française de Pharmacologie et Thérapeutique-SFPT) and the French Society of Anaesthesia and Intensive Care Medicine (Société Française d'Anesthésie et Réanimation-SFAR)

BACKGROUND

Beta-lactam antibiotics (βLA) are the most commonly used antibiotics in the intensive care unit (ICU). ICU patients present many pathophysiological features that cause pharmacokinetic (PK) and pharmacodynamic (PD) specificities, leading to the risk of underdosage. The French Society of Pharmacology and Therapeutics (SFPT) and the French Society of Anaesthesia and Intensive Care Medicine (SFAR) have joined forces to provide guidelines on the optimization of beta-lactam treatment in ICU patients.

METHODS

A consensus committee of 18 experts from the two societies had the mission of producing these guidelines. The entire process was conducted independently of any industry funding. A list of questions formulated according to the PICO model (Population, Intervention, Comparison, and Outcomes) was drawn-up by the experts. Then, two bibliographic experts analysed the literature published since January 2000 using predefined keywords according to PRISMA recommendations. The quality of the data identified from the literature was assessed using the GRADE® methodology. Due to the lack of powerful studies having used mortality as main judgement criteria, it was decided, before drafting the recommendations, to formulate only "optional" recommendations.

RESULTS

After two rounds of rating and one amendment, a strong agreement was reached by the SFPT-SFAR guideline panel for 21 optional recommendations and a recapitulative algorithm for care covering four areas: (i) pharmacokinetic variability, (ii) PK-PD relationship, (iii) administration modalities, and (iv) therapeutic drug monitoring (TDM). The most important recommendations regarding βLA administration in ICU patients concerned (i) the consideration of the many sources of PK variability in this population; (ii) the definition of free plasma concentration between four and eight times the Minimal Inhibitory Concentration (MIC) of the causative bacteria for 100% of the dosing interval as PK-PD target to maximize bacteriological and clinical responses; (iii) the use of continuous or prolonged administration of βLA in the most severe patients, in case of high MIC bacteria and in case of lower respiratory tract infection to improve clinical cure; and (iv) the use of TDM to improve PK-PD target achievement.

CONCLUSIONS

The experts strongly suggest the use of personalized dosing, continuous or prolonged infusion and therapeutic drug monitoring when administering βLA in critically ill patients.

Isavuconazole Kinetic Exploration for Clinical Practice

BACKGROUND

Isavuconazole is a new antifungal prodrug for the treatment of invasive aspergillosis and mucormycosis. As no clear pharmacokinetic-pharmacodynamic relationship has been established for patients, therapeutic drug monitoring is not currently required. However, as isavuconazole is a new drug, clinicians are sometimes sceptical about the exposure achieved in their patients and seek pharmacokinetic exploration. A minimal response consists of determining that the patient's pharmacokinetic profile agrees with profiles reported by Desai et al. using concentrations from the SECURE study.

METHODS

Based on one concentration and Desai et al.'s population-pharmacokinetic model, it is possible to estimate a patient's most likely pharmacokinetic profile. If a patient's pharmacokinetic profile is close to the profiles reported by Desai et al., therapeutic drug monitoring is not required. In contrast, when the pharmacokinetic profile differs from the Desai et al. profiles, isavuconazole concentration monitoring and pharmacokinetic profile modeling are the only methods for obtaining information on a patient's exposure and the efficacy of isavuconazole.

RESULTS

Four patients presented with surprising pharmacokinetic profiles, unexplained by drug interactions or cytochrome P450 3A4/5 polymorphisms. For two of them, a drug dosage adjustment was proposed and applied by clinicians, together with a check for a new pharmacokinetic profile a few days later.

CONCLUSIONS

Collecting one blood sample just before the first maintenance dose to make an early estimation of the patient's most likely pharmacokinetic profile is one method of identifying patients with outlier pharmacokinetic behavior.

Efavirenz and Lopinavir Levels in HIV-Infected Women and Their Nursing Infants, in Mali

Limited data are currently available on antiretroviral pharmacokinetics in breast milk (BM) and in breastfed infants' blood. To explore these parameters in patients in Mali, we measured plasma antiretroviral levels in human immunodeficiency virus (HIV)-infected mothers and their breastfed infants over 6 months. We specifically analyzed the concentrations of efavirenz (EFV) and lopinavir (LPV) in the plasma of mothers living with HIV and their breastfed infants. Blood samples were collected at delivery and at month 1, 3, and 6 postpartum. EFV and LPV concentrations were measured by liquid chromatography-tandem mass spectrometry. HIV-1 RNA load was measured by Abbott M2000RT RealTime System at delivery and 6 months postpartum for mothers, and at 3 and 6 months postbirth for infants. The median duration of antiretroviral therapy at study inclusion was 57 months [interquartile range (IQR), 0-168 months]. The median EFV ratios of infant plasma/maternal plasma (MP) were 0.057 at month 1, 0.072 at month 3, and 0.048 at month 6. During the study period, the median BM/MP ratio of EFV was 1.16 (IQR, 0.96-20.62), which corresponds to a relative infant dose of 2.46% of the recommended weight-adjusted pediatric EFV dose at month 6. The apparent infant clearance of EFV was 0.146 l/h per kilogram at month 6. The LPV concentrations in the plasma of all infants were undetectable. No drug-related adverse reaction or toxicity was observed in any of the infants. The two women who presented a viral load of >50 copies/ml at month 6 had undetectable plasma drug concentrations at the same period. This study showed that breastfed infants received a low level of EFV but not LPV from their treated mothers.

Antiretroviral unbound concentration during pregnancy: piece of interest in the puzzle?

Atazanavir and darunavir total concentrations (drug bound to plasma proteins plus unbound drug) progressively decrease during pregnancy. This pharmacokinetic variation leads physicians to recommend increasing doses. Conversely, the unbound concentration (Cu), i.e. the pharmacologically active form of the drug, remains unchanged. The explanation of this desynchronization lies in the fact that the clearance of the unbound form, corresponding to the intrinsic metabolic capacity of the hepatocytes, is the only factor driving Cu, and is constant during pregnancy. The attention of HIV physicians should be attracted to this aspect of pharmacokinetics, which is often incompletely understood and could lead to inadequate dose adjustment, which could then cause overexposure of the foetus for many months, with unknown consequences.

Determination of dolutegravir's unbound fraction in human plasma using validated equilibrium dialysis and LC-MS/MS methods

Assessment of the unbound pharmacologically active fraction (fu; as the ratio of unbound to total concentration) of dolutegravir could improve therapeutic drug monitoring (TDM) in patients that experience virological failure or toxicity, despite receiving adequate total concentrations. This study evaluated (i) dolutegravir's fu through equilibrium dialysis (ED), (ii) the pre-analytical parameters that influence fu, and (iii) fu's inter-individual variability in HIV patients. Validation of the LC-MS/MS method followed FDA guidelines. The results, based on coefficients of variation (results from nominal concentrations <15%), allowed accurate measurement of unbound and total dolutegravir concentrations. Equilibrium during ED was obtained in 4h. Sparse non-specific binding (9%) was observed, allowing results interpretation without interference. Steps before analysis (e.g., conservation at +4°C, freeze/thaw cycles) did not influence fu, allowing easy integration of fu analysis within laboratory routines. Anticoagulants from samples (citrated versus heparinized; p<0.001) and hemolysis (p=0.007) influenced fu and could lead to misinterpretation. Developed was then performed to the HIV-patients' plasma (n=54). Results, expressed as median InterQuartile Range [25%;75%] were 0.45% IQR [0.38; 0.55] for fu, 9.26μg/L IQR [4.62; 15.14] for unbound, and 2035μg/L IQR [878.5; 2640] for total concentration. The high inter-individual variability observed in the unbound form from HIV patients was a first step towards integrating dolutegravir TDM.

Patient emergency assessment following deliberate self-poisoning with benzodiazepines: Can cognitive markers predict recall of the psychiatric interview? A pilot study

STUDY HYPOTHESIS

In cases of deliberate self-poisoning (DSP), patients often ingest benzodiazepines (BZDs), known to alter memory. Experts recommend recovery of the patient's cognitive capacity before psychiatric assessment. Unfortunately, there is no validated tool in common practice to assess whether sufficient cognitive recovery has occurred after DSP with BZDs to ensure patient memory of the assessment.

OBJECTIVE

The aim of the study was to identify cognitive functions and markers which predict preserved memory of the mental health care plan proposed at the emergency department after DSP.

METHODS

We recruited patients admitted for DSP with BZDs and control patients. At the time of the psychiatric assessment, we performed cognitive tests and we studied the relationship between these tests and the scores of a memory test performed 24 h after.

RESULTS

In comparison with the control group, we found memory impairment in the BZD group. We found significant impairment on the Trail Making Test A (TMT A) in the BZD group in comparison with the control group, while TMT A and Wechsler Adult Intelligence Scale (WAIS) Coding test scores were significantly correlated with memory scores.

CONCLUSIONS

Attentional functions tested by WAIS Coding test and TMT A were correlated with memory score. It could be profitable to assess it in clinical practice prior to a psychiatric interview.

Is the unbound concentration of atazanavir of interest in therapeutic drug monitoring?

To date, therapeutic drug monitoring (TDM) is carried out with antiretrovirals and is usually based on total concentrations (C_t ). However, for some patients, TDM does not reflect efficacy or the avoidance of toxicity as is the case for atazanavir (ATV), a HIV protease inhibitor. As the unbound concentration (C_u ) is the pharmacological active form, the aim of the study was to evaluate the value of C_u and the unbound fraction (f_u , f_u = C_u /C_t ) for the TDM of ATV. The variability of C_u and the corresponding f_u of ATV was explored in 43 patients treated with ATV for an average of 13.5 months. C_u was determined by coupling ultrafiltration and liquid chromatography. As ATV is highly bound to alpha-1 acid glycoprotein (AAG), the correlation between f_u and AAG was also evaluated. The viral load was monitored to evaluate the patients' virologic response, while total plasma bilirubin and unconjugated plasma bilirubin were used as biomarkers of ATV toxicity. Median trough C_u and C_t were 37.9 μg/L (Interquartile range (IQR) 20.6-94.9 μg/L) and 628.6 μg/L (IQR 362.7-1078.1 μg/L), respectively. f_u , C_u and C_t showed high variability, but the f_u variability was not correlated with the AAG level. The unbound concentration and fraction were unrelated to the virologic response (P = 0.21 and P = 0.65 for C_u and f_u , respectively) nor to the unconjugated bilirubin (Pearson correlation coefficient (ρ), ρ = 0.22; P = 0.17 for C_u ). Neither total nor unbound concentrations of ATV fully explained hyperbilirubinaemia or virologic failure. From this study, we conclude that unbound ATV did not appear to be more relevant than C_t .

Mycophenolic Acid Pharmacokinetics and Relapse in Children with Steroid-Dependent Idiopathic Nephrotic Syndrome

BACKGROUND AND OBJECTIVES

Therapeutic drug monitoring of mycophenolic acid can improve clinical outcome in organ transplantation and lupus, but data are scarce in idiopathic nephrotic syndrome. The aim of our study was to investigate whether mycophenolic acid pharmacokinetics are associated with disease control in children receiving mycophenolate mofetil for the treatment of steroid-dependent nephrotic syndrome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a retrospective multicenter study including 95 children with steroid-dependent nephrotic syndrome treated with mycophenolate mofetil with or without steroids. Area under the concentration-time curve of mycophenolic acid was determined in all children on the basis of sampling times at 20, 60, and 180 minutes postdose, using Bayesian estimation. The association between a threshold value of the area under the concentration-time curve of mycophenolic acid and the relapse rate was assessed using a negative binomial model.

RESULTS

In total, 140 areas under the concentration-time curve of mycophenolic acid were analyzed. The findings indicate individual dose adaptation in 53 patients (38%) to achieve an area under the concentration-time curve target of 30-60 mg·h/L. In a multivariable negative binomial model including sex, age at disease onset, time to start of mycophenolate mofetil, previous immunomodulatory treatment, and concomitant prednisone dose, a level of area under the concentration-time curve of mycophenolic acid >45 mg·h/L was significantly associated with a lower relapse rate (rate ratio, 0.65; 95% confidence interval, 0.46 to 0.89; P=0.01).

CONCLUSIONS

Therapeutic drug monitoring leading to individualized dosing may improve the efficacy of mycophenolate mofetil in steroid-dependent nephrotic syndrome. Additional prospective studies are warranted to determine the optimal target for area under the concentration-time curve of mycophenolic acid in this population.