Guillaume Deslandes

A liquid chromatography assay for a quantification of doripenem, ertapenem, imipenem, meropenem concentrations in human plasma: Application to a clinical pharmacokinetic study

A simple chromatographic assay based on ultra high performance liquid chromatography with ultraviolet detection at 295 nm is proposed to determinate simultaneously human plasma concentrations of imipenem, doripenem, meropenem and ertapenem. After deproteinization by acetonitrile, carbapenems are separated on a PentaFluoroPhenyl column with a binary gradient elution. This method is specific, accurate, precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%), sensitive (the limit of quantitation is equal to 0.50 mg/L for imipenem, doripenem, ertapenem, meropenem) and not time consuming (run time=7 min). An application of this method to measure ertapenem plasma concentrations in burn patients is presented.

Colchicine-induced rhabdomyolysis in a heart/lung transplant patient with concurrent use of cyclosporin, pravastatin, and azithromycin.

We report a case of colchicine-induced rhabdomyolysis in a heart/lung-transplanted man treated with cyclosporin. A treatment was to resolve an acute gouty arthritis and was started with 3 mg of colchicine the first day, then 2 mg the second and the third day, and finally 1 mg/d during 6 days. Eight days later, the patient developed multiple organ failure and rhabdomyolysis. The concentration of colchicine analyzed was greater than the standard 153 hours after his last intake. Pharmacokinetic interactions are responsible of this toxicity. Cyclosporin, pravastatin, and azithromycin are known to inhibit P-glycoprotein, which will enhance the intracellular colchicine level by acting in its bioavailability and moderating hepatic and renal excretion. Moreover, long-term treatment by cyclosporin generates chronic renal failure that will, in the same time, decrease colchicine elimination. Even short-term administration of therapeutic colchicine dose may cause colchicine-related toxicity, especially in the setting of a renal failure and/or polymedicinal treatment.

Influence of glomerular filtration rate on the clearance of vancomycin administered by continuous infusion in burn patients

The relationship between clearance of vancomycin administered by continuous infusion and the glomerular filtration rate (GFR) estimated by creatinine clearance (CL(Cr)) was investigated in a large cohort of burn patients. Individual vancomycin clearance (CL(Van)) was estimated from the ratio between the rate of infusion and the plasma concentration at steady state for 70 patients (149 samples). The average value of CL(Van) (7.03+/-3.79 L/h) was higher than normal values in non-burn patients. A significant relationship between CL(Van) versus CL(Cr) was found (r=0.506; P<0.001): CL(Van) (L/h)=0.0205CL(Cr)(mL/min)+3.47. From this result, a simple formula is proposed to adapt vancomycin dosage: rate of vancomycin continuous infusion (g/day)=[0.0205CL(Cr) (mL/min)+3.47] x [target vancomycin concentration at steady state (mg/L)] x (24/1000). The limits of the predictive performance of this formula are discussed, since factors other than GFR can affect vancomycin elimination. This formula could help clinicians to define the optimum vancomycin dosage, particularly in patients with disturbed renal function.

A fast LC-MS/MS assay for methotrexate monitoring in plasma: validation, comparison to FPIA and application in the setting of carboxypeptidase therapy

High-dose methotrexate remains a mainstay in the treatment of acute lymphoblastic leukaemia, osteosarcoma and non-Hodgkin lymphoma. Therapeutic drug monitoring of plasma MTX is important to monitor efficacy and adverse events. The authors aimed at developing a liquid chromatography tandem mass spectrometry (LC-MS/MS) method with online extraction to determine MTX and 7-OH-MTX in plasma for therapeutic drug monitoring. The analysis combined straightforward sample preparation, consisting of protein precipitation with methanol/ZnSO4, with a 4-minute run time consisting of an on-line enrichment by a flush/back-flush cycle (Poros column, R1/20, 2.1 mm × 30 mm) before the second dimension chromatography (Phenomenex Luna 5 μm Phenyl Hexyl, 2 mm × 50 mm column). Samples were analysed using an HPLC Agilent 1200 Series and ABSciex API 3200. The electrospray was operated in positive ionization mode monitoring the following mass transitions: m/z 455.11 → 308.3 for MTX, 471.14 → 324.3 for 7-OH-MTX and m/z 459.1 → 312.3 for internal standard (MTX13C2H3). The method was linear up to 50 μmol L−1, and intra-day and inter-day quality control CVs were below 8.3% for MTX and 11.71% for 7-OH-MTX. Average recovery was 24% for MTX and 57% for 7-OH-MTX. The lower limit of quantitation was 25 nmol L−1 for the 2 analytes. For MTX and 7-OH-MTX the standard line slope CV percentage was <3% and the slope difference <6%, indicating that our analytical method is almost free from a significant relative matrix effect. Method comparison with the Abbott TDx fluorescent polarization immunoassay (FPIA) showed excellent agreement: LC-MS/MS = 0.0011 + 1.0334 (FPIA). Because of antibody cross-reactivity between DAMPA and MTX, none of the immunoassays can be used after carboxypeptidase administration. The goal of our work was to develop a specific LC-MS/MS method to monitor both MTX and 7-OH-MTX plasma concentrations within the clinically relevant range. Its expected that the LC-MS/MS method for MTX monitoring after carboxypeptidase administration will be very rarely used since it concerns only exceptional cases. Therefore, the geographically balanced distribution of University Hospital able to ensure follow-up of these patients, within 24 hours of collection, can draw a reliable solution for the security of the patients. We develop a fast and reliable LC-MS/MS method for both routine TDM of MTX as in the setting of carboxypeptidase therapy.

A liquid chromatography–tandem mass spectrometry assay for quantification of rilpivirine and dolutegravir in human plasma

A liquid chromatography-tandem mass spectrometry assay requiring a 100μL aliquot of human plasma for simultaneous determination of rilpivirine, a second generation non-nucleoside reverse transcriptase inhibitors of HIV and dolutegravir, a novel integrase stand transfer inhibitors of HIV concentrations has been developed. Sample pre-treatment is limited to protein precipitation with a mixture of methanol and zinc sulfate. After centrifugation the supernatant is injected in the chromatographic system, which consists of on-line solid phase extraction followed by separation on a phenyl-hexyl column. This 2.5min method, with its simple sample preparation provides sensitive (the limit of quantitation is 25ng/mL for each compound), accurate and precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%) quantification of the plasma concentration of these drugs and can be used for therapeutic drug monitoring in patients infected with HIV.

Crushed and Injected Buprenorphine Tablets: Characteristics of Princeps and Generic Solutions

Self-injection of high-dose buprenorphine is responsible for well-described complications. In 2011, we have been alerted by unusual but serious cutaneous complication among injection buprenorphine users. A prospective data collection identified 30 cases of necrotic cutaneous lesions after injection of filtered buprenorphine solution, among which 25 cases occurred following injection of buprenorphine generics. The main goal of our study was to put forward particularities that could explain the cutaneous complications, by qualitatively and quantitatively confronting particles present in Subutex and generics solutions. We used the same protocol that injected-buprenorphine users: generic or subutex tablets were crushed in sterile water and filtered through 2 filters commonly used (cotton-pad and sterifilt). Solutions were analyzed by laser granulometry, flow cytometry and scanning electron microscopy. We have highlighted the wide variation of the quantity and the size of the particles present in solution between the two drugs after cotton-pad filtration. The proportion of particles <10 µm is systematically higher in the generic solutions than with Subutex. All of the insoluble particles found in generic solutions contain silica, whereas non- organic element was to be identified in the insoluble particles of Subutex. One skin biopsy obtained from one patient who developed a necrotic lesion after intravenous injection of filtrated solution of buprenorphine generic, shows non-organic elements. Identification of particles in situ enables us to confirm the presence of silica in the biopsy. Actually the monitoring of patient receiving generic of buprenorphine must be strengthened.

Pharmacokinetics of ertapenem in burns patients.

The aims of this study were to evaluate pharmacokinetic (PK) parameters of total and unbound ertapenem (ERT) in burns patients and to identify which covariates influence these PK parameters. ERT plasma concentrations were measured in burns patients (n = 8) who received a 0.5-h infusion of ERT (1000 mg) every 24 h. PK parameters were estimated by a non-compartmental approach and the influence of covariates was estimated by multivariate analysis using a population approach. Clearance (CL) and the volume of distribution (V) of total ERT were lower than the results for unbound ERT [CL, 22.2 ± 5.6 mL/min vs. 279.4 ± 208.2 mL/min; V, 9.7 ± 1.4L vs. 120.6 ± 130.6L (mean ± standard deviation)]. Creatinine clearance (CL(Cr)) and the burned surface area (BSA) were the covariates identified that significantly (P<0.01) affected the pharmacokinetics of total ERT [CL (L/h)=0.373 +{0.00666 x CL(Cr) (mL/min)}] and unbound ERT [peripheral volume of distribution (L) = 3.05 + {0.959 x BSA (% of the total body surface)}], respectively. The influences of albuminaemia, glomerular filtration and burn wound on ERT pharmacokinetics are proposed to explain these results. These first results support that the ERT plasma concentration should be closely monitored particularly for patients with high values of BSA and/or CL(Cr) to avoid suboptimal exposure.

Comparison between a liquid chromatography-tandem mass spectrometry assay and a fluorescent polarization immunoassay to measure whole blood everolimus concentration in heart and renal transplantations.

Various methods [fluorescent polarization immunoassay (FPIA) and liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) assay] are used for therapeutic drug monitoring of everolimus. The aim of this study is to compare these assays in renal and heart transplantation. The correlation between results was investigated by linear regression in 44 patients (24 heart recipients and 20 renal recipients—137 samples). The comparison between assays was performed by a paired t‐test. A highly significant correlation was found between FPIA and LC‐MS/MS in heart and renal recipients [FPIA=0.851 × LC‐MS/MS+1.773r2=0.8738 (P<0.001)]. Paired t‐tests did not show a significant difference between everolimus whole blood concentrations in the populations of heart and renal recipients or heart recipients or renal recipients. FPIA and LC‐MS/MS assays gave consistent overall results although some significant differences were observed in some samples between these methods indicating that FPIA assay has limitations that deserve further investigations. J. Clin. Lab. Anal. 22:282‐285, 2008.

Chiral on-line solid phase extraction coupled to liquid chromatography-tandem mass spectrometry assay for quantification of (R) and (S) enantiomers of methadone and its main metabolite in plasma

The authors aimed at developing a liquid chromatography tandem mass spectrometry (LC-MS/MS) method with online extraction to determine (R)- and (S)- methadone enantiomers and its main metabolite 2-ethylidine-1,5-dimethyl-3,3 diphenylpyrrolidine (EDDP) in plasma. The analysis combined straightforward sample preparation, consisting of protein precipitation with acetonitrile, and an online enrichment by a flush/back-flush cycle before the second dimension chromatography. Using D3-deuterated internal standards allows overcoming significant relative matrix effect. Our method was linear up to 2000 ng/mL. This simple sample preparation provides sensitive (the limit of quantitation is 25 ng/mL for (R,S)-methadone and EDDP and 12.5 ng/mL for (R)- and (S)- methadone), accurate and precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%) quantification of the plasma concentration of these drugs. We have developed a reliable LC-MS/MS method for both routine therapeutic drug monitoring and pharmacokinetics studies and for toxicology analysis in the setting of methadone treatment or intoxication.

Influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1

OBJECTIVES The metabolic pathways of dolutegravir and nevirapine suggest a potential pharmacokinetic interaction between these drugs. The objective of this study was to investigate the influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1. PATIENTS AND METHODS This study was an investigator-initiated trial registered at ClinicalTrials.gov under identifier NCT02067767. Dolutegravir (50 mg once daily) was added to the antiretroviral regimen (400 mg of nevirapine once daily + 600/300 mg of abacavir/lamivudine once daily) in 10 adult patients for 5 days. After discontinuation of nevirapine, the combination of dolutegravir + abacavir/lamivudine was continued. Full pharmacokinetic profiles were assessed on the day of nevirapine discontinuation and 2 weeks after discontinuation of nevirapine. The pharmacokinetic parameters of dolutegravir were calculated by non-compartmental analysis. The log-transformed values of these parameters were compared between periods with and without nevirapine co-administration. RESULTS The co-administration of nevirapine led to a significant decrease (P < 0.05) in the area under the plasma concentration-time curve for dolutegravir from the time the dose was administered until the end of the dosing interval (-19%, P = 0.011), as well as decreases in trough plasma concentration (-34%, P = 0.018) and terminal half-life (-15%, P = 0.039), and a significant increase (P < 0.05) in apparent oral clearance for dolutegravir (+23%, P = 0.011). CONCLUSIONS The decrease in dolutegravir exposure in combination with nevirapine suggests that the metabolism of dolutegravir is induced by nevirapine. According to therapeutic drug monitoring for dolutegravir, some patients may need a higher dose than 50 mg of dolutegravir once daily to maintain the therapeutic plasma concentration throughout the dosing interval.