Sarah Djabarouti

Pharmacokinetics and intrapulmonary diffusion of levofloxacin in critically ill patients with severe community-acquired pneumonia.

Objective:To determine the steady-state plasma and epithelial lining fluid concentrations of intravenous levofloxacin, 500 mg, administered once or twice daily in critically ill patients with severe community-acquired pneumonia. Design:Prospective, open-label study. Setting:An intensive care unit and a clinical pharmacokinetic laboratory in two university hospitals. Patients:Twenty-four adult patients with severe community-acquired pneumonia and receiving mechanical ventilation were enrolled. Interventions:All subjects received 1-hr intravenous infusions of 500 mg levofloxacin once or twice daily. The plasma and epithelial lining fluid levofloxacin concentrations were determined at steady-state after 2 days of therapy with high-performance liquid chromatography. Measurements and main results:The median (interquartile range [IQR]) plasma and epithelial lining fluid peak levofloxacin concentrations were 12.6 (IQR, 12.0–14.1) and 11.9 (IQR, 8.7–13.7) mg/L, respectively, in the once-daily group and 19.7 (IQR, 19.0–22.0) and 17.8 (IQR, 16.2–23.5) mg/L in the twice-daily group, showing a pulmonary percentage penetration of >100% in both groups. The median (IQR) total body exposures were 151 (IQR, 137–174) and 416 (IQR, 406–472) mg·hr/L, respectively, in the once-daily and twice-daily groups. Conclusions:Our results suggest that in critically ill patients who are receiving mechanical ventilation and have severe community-acquired pneumonia and creatinine clearance of >40 mL/min, the administration of 500 mg of intravenous levofloxacin once and twice daily allows for the exceeding of pharmacodynamic thresholds predictive of outcome (i.e., peak concentration to minimum inhibitory concentration ratio of >10 or area under concentration-time curve to minimal inhibitory concentration ratio of >125 hrs) both in serum and epithelial lining fluid for pathogens with minimum inhibitory concentration values of ≤1 mg/L and >1 mg/L, respectively.

Steady-state mycophenolate mofetil pharmacokinetic parameters enable prediction of systemic lupus erythematosus clinical flares: an observational cohort study.

IntroductionThe aim of this study was to determine whether mycophenolate mofetil (MMF) pharmacokinetics (PK) under combined MMF and prednisone remission-maintenance therapy can predict systemic lupus erythematosus (SLE) clinical flares.MethodsAt inclusion, steady-state PK parameters of the MMF active form, mycophenolic acid (MPA), and its glucuronide metabolite (MPAG) were determined for 25 stable SLE patients without renal manifestations. Disease activity was assessed during 6 months of follow-up. Potential relationships between those entry MMF-PK variables and clinical outcome were analyzed.ResultsMMF controlled disease activity in 17 patients (successes) and failed to do so for 8 others (failures). For failures and successes, respectively, entry MPA areas under the time-concentration curve between 0 and 12 hours (AUC0-12 h) (medians: 37.7 vs 73.1 mg/h/L, P = 0.003) and MPA 12-hour trough concentrations (C12 h) (medians: 1.5 vs 3.7 mg/L, P = 0.008) were significantly lower, and inclusion MPAG/MPA C12 h ratios (medians: 18.7 vs 10.2, P = 0.02) were significantly higher. According to our receiver operating characteristics curve analysis, MPA C12 h was best able to discriminate a flare during follow-up (93% sensitivity, 85% specificity). A 3-mg/L cut-off had 92% negative-predictive value for developing a flare during follow-up.ConclusionsFor our SLE patients without renal manifestations, clinical flares developing under maintenance therapy were associated with steady-state inclusion MPA C12 h < 3 mg/L.

Therapeutic drug monitoring of mycophenolate mofetil and enteric-coated mycophenolate sodium in patients with systemic lupus erythematosus

Objective: Mycophenolic acid (MPA), the active form of mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS), is used to treat systemic lupus erythematosus (SLE). MMF and EC-MPS pharmacokinetics were examined to devise guidance for therapeutic drug monitoring (TDM) for SLE patients with normal renal function. Research design and methods: This observational study included 21 patients receiving MMF (1000 mg twice daily) and 14 taking EC-MPS (720 mg twice daily). MPA AUC between 0 and 12 h (AUC0–12h), Cmax, Tmax, and 12-h trough concentrations (C12h) were determined. Results: Means of dose-normalized MMF– or EC-MPS–MPA Cmax were 64.6 ± 25 and 61.4 ± 27.1 h mg/l, respectively. MPA Tmax for EC-MPS was longer and more variable than for MMF. MMF-MPA AUC0–12h and C12h were correlated (r = 0.78, p = 0.0001), but EC-MPS–MPA Cmax and single concentrations were weakly correlated. A limited-sampling strategy (LSS) combining Cmax and C12h gave satisfactory predictive performance to estimate MPA AUC0–12h after EC-MPS administration. Conclusions: For TDM in SLE patients with GFR > 60 ml/min/1.73 m2, C12h after MMF ingestion could predict MPA AUC0–12h, while an LSS around Tmax should be used for patients on EC-MPS.

A sensitive liquid chromatography coupled with mass spectrometry method for the intracellular and plasma quantification of raltegravir after solid-phase extraction

Introduction  Liquid chromatography coupled with mass spectrometry for the quantification of raltegravir in human plasma and peripheral blood mononuclear cells has been developed.

A new reliable, transposable and cost-effective assay for absolute quantification of total plasmatic bevacizumab by LC–MS/MS in human plasma comparing two internal standard calibration approaches

The quantification of monoclonal antibodies (mAbs) such as bevacizumab, a recombinant humanized immunoglobulin G1 (hIgG1), in biological fluids, is an essential prerequisite to any pharmacokinetic preclinical and clinical study. To date, reference techniques used to quantify mAbs rely on enzyme-linked immunosorbent assay (ELISA) lacking specificity. Furthermore, the commercially available ELISA kit to quantify bevacizumab in human plasma only assesses the free fraction of the drug. However, the conditions of storage and analysis of plasma samples could alter the physiological equilibrium between the free, bound and partially bound forms of bevacizumab and this could result in over- or underestimation of drug concentration. We developed a new assay for absolute quantification of total fraction of bevacizumab by liquid chromatography tandem mass spectrometry (LC-MS/MS) basing identification and quantification of bevacizumab on two specific peptides. In this report we compare our assay with two internal standard (IS) calibration approaches: one using a different human mAb (Trastuzumab) and the other using a stable isotope labeled specific peptide. After enrichment by affinity chromatography on protein A and concentration by ultrafiltration, human plasma samples were proteolyzed by trypsin. Linearity was established from 12.5 to 500μg/mL with an interday accuracy ranging from 101.7 to 110.6% and precision from 7.0% to 9.9%. This study demonstrates the importance of the choice of the IS in quantifying bevacizumab in human plasma and highlights the difficulty of reaching a reliable proteolysis with a sufficient recovery. We developed a reliable and cost-effective LC-MS/MS method to quantify total plasmatic fraction of bevacizumab in human plasma. Through our development we proposed a generic methodology easily transposable to quantify all IgG1 subclass very useful for clinical pharmacokinetics studies.

Chemical stability of azacitidine suspensions for injection after cold-chain reconstitution of powder and storage

PURPOSE The 72-hour chemical stability of refrigerated syringes of azacitidine suspension prepared via a cold-chain method is investigated. METHODS Three 25-mg/mL azacitidine suspensions were prepared from different lots of powdered drug. The suspensions were stored in 2-mL polypropylene syringes at 2-8 °C and protected from light. The concentrations of azacitidine and the mean area under the concentration-time curve (AUC) values for its degradation products were determined after 0, 1, 2, 3, 4, 6, 8, 12, 24, 48, and 72 hours using high-performance liquid chromatography with ultraviolet detection. RESULTS The degradation process was slow during the first 48 hours and then accelerated. During the first 48 hours of storage, 4.23% of the azacitidine was lost relative to the mean concentration measured at time zero, which complied with International Conference on Harmonisation (ICH) guidance specifying a maximum change of 5% from the initial measured value. Two degradation products were present immediately after syringe preparation; N-formylribosylguanylurea formed rapidly (as indicated by a 35.62% increase from the baseline AUC in the first 12 hours), whereas ribosylguanylurea formation occurred more slowly (a 7.69% mean increase from the baseline AUC at 12 hours) but then rapidly accelerated. The study results indicate that properly prepared azacitidine syringes for injection can be administered up to two days later while maintaining conformance with ICH stability standards. CONCLUSION Azacitidine 25-mg/mL suspensions reconstituted with refrigerated water (2-8 °C) and stored in propylene syringes were chemically stable during the first 48 hours when stored protected from light at 2-8 °C.