An ultra performance liquid chromatography-tandem mass spectrometry method for the therapeutic drug monitoring of isavuconazole and seven other antifungal compounds in plasma samples.

A new analytical method was developed for the routine Therapeutic Drug Monitoring of 8 antifungals compounds in 50µL of plasma: isavuconazole (ISZ), voriconazole (VRZ), posaconazole (PSZ), fluconazole (FCZ), caspofungin (CSF), flucytosine (5FC), itraconazole (ITZ) and its metabolite OH-itraconazole (OH-ITZ). After adding 50µL of the internal standard, which consisted in a mixture of the deuterated isotopes of the quantified compounds, the sample treatment consisted in a simple protein precipitation with 400µL of acetonitrile. Five microliters of the supernatant were directly injected into the chromatographic system. The chromatographic separation was performed with a Waters C18-BEH column and a mobile phase consisting in a mixture of water and acetonitrile, both containing 0.1% of formic acid. The total run time was 3min and the detection of the analytes was performed by electrospray ionization in a positive mode using selected reaction monitoring. Intra and inter-day precision and inaccuracy were <15% over the calibration ranges that were determined according to their clinical relevance: 0.20-20.0mg/L for ISZ, VRZ, PSZ, ITZ, and OH-ITZ; 0.50-50.0mg/L for FCZ and CSF; 2.00-200mg/L for 5FC. This simple and fast method was found suitable for routine therapeutic drug monitoring.

Optimize administration protocol of capecitabine plus docetaxel combination in metastatic breast cancer patients.

Combining several cytotoxics is the current mainstay for treating breast cancer patients. The combination between capecitabine and docetaxel was found to be more efficient than capecitabine or docetaxel when both were used as single agents. However, the administration protocol for this combination has been empirically chosen from single-agent trials. Based on already available population analysis, we propose here to optimize the administration protocol of this association so as to enhance efficacy while limiting treatment-related toxicity. Efficacy parameters evaluated from population analysis using a disturbed tumor growth model and safety characteristics from the available databases evidenced that: 1) Docetaxel is more efficient than capecitabine at the start of the treatment, but becomes less efficient next because of acquisition of resistance; 2) Over a long period of time, capecitabine is better tolerated than docetaxel. These characteristics allowed the following recommendations for an optimized modality of combination: 1) The treatment has to be started at the maximum tolerated dose for docetaxel; this dose should be individualized right from the start of the second cycle of treatment; 2) In parallel, capecitabine has to be started at a dose lower than its maximum tolerated dose. 3) When docetaxel becomes less efficient than capecitabine because of resistance, docetaxel dose has to be reduced but not discontinued. 4) If adverse events show during the treatment, it is recommended to reduce docetaxel, rather than capecitabine dosage. Combining modeling and statistical analysis of clinical data permit to optimize combination treatments. This procedure could be extended to others treatments involving combination of several cytotoxics.

Progress in strategies for dosage regimen individualization.

Several findings suggest that patient outcome would be improved with individualized doses. The aim of this paper is to describe major approaches, methods and underlying basic foundations implemented, in clinical practice, for dosage individualization. Also we propose a new method codified by kinetic nomograms as reliable alternative to traditional Bayesian methods. Clinical and simulation data were reported to evaluate performances of the proposed methods. Real examples of therapeutic drug monitoring were selected. Bayesian methods were used to individualize high-dose methotrexate rate infusion and amikacin dosage regimen, and kinetic nomograms to adjust sirolimus doses. 1) Using only few measurements, Bayesian method resulted in accurate estimates of individual pharmacokinetic parameters of high dose methotrexate infusion. Targeting a pre-defined end-of-infusion level, infusion rate was individualized according to the previously obtained pharmacokinetic parameters. 2) With the same reasoning, individual pharmacokinetic parameters of amikacin were obtained by Bayesian estimation using three individual samples. Subsequent dosage adjustment allowed achievement of therapeutic goals at steady state. 3) Without computing individual pharmacokinetic parameters, nor using pharmacokinetic software, kinetic nomograms steered individual sirolimus blood levels within its therapeutic window with only two samples and in the first week after starting treatment. This contribution relates traditional Bayesian methods developed in 80's but not yet fully integrated in clinical context because of their complexity. The contribution focuses on recent developments based on population approaches, rendering the dosage adjustment methodology a simple and quick bedside application.

Population pharmacokinetic analysis of 5-FU and 5-FDHU in colorectal cancer patients: search for biomarkers associated with gastro-intestinal toxicity.

PURPOSE: The anticancer drug 5-fluorouracile (5-FU) which is indicated for the treatment of a variety of solid malignancies such as colorectal, breast, head and neck neoplasms is extensively biotransformed to 5 fluoro-5,6- dihydrouracil (5-FDHU) by the dihydropyrimidine deshydrogenase enzyme (DPD). DPD deficiency is recognized as an important risk factor, predisposing patient to undergo severe/lethal toxicities. To date, relationships between 5-FU, 5- FDHU and toxicity following i.v. bolus administration has not been studied using the population pharmacokinetics approach. METHODS: Retrospective pharmacokinetic data of 5-FU and 5-FDHU from 127 colorectal cancer patients were used for the population pharmacokinetic analysis. Treatment schedule consisted of an adjuvant therapy with 5-FU plus leucovorin. 5- FU and 5-FDHU complete plasma profiles recorded on day-1 of the first chemotherapy cycle were modeled simultaneously using NONMEM software. Gastro-intestinal adverse events graded according to the WHO criteria were recorded after the first cycle. A population logistic regression model was developed to identify predictive factors of these adverse events. RESULTS: A three-compartment pharmacokinetic mixture model best described 5-FU and 5-FDHU kinetics profiles. Linear and saturated elimination from the central compartment of 5-FU and a linear elimination from the 5-FDHU compartment were used. A bimodal distribution of the inter-compartmental clearance was observed allowing two subpopulation with high (17 L/h) and low values (3.35 L/h). DPD-phenotype is suspected to explain this mixture. No covariates were introduced in the final model. Also, no relationship was found between maximal metabolism rate and DPD-phenotype. Predictive factors associated with occurrence of high grade gastro-intestinal adverse events were gender, dose and lean body mass suggesting serious cautions with the BSA-weighted dose for women. For the low-grade toxicities, 5-FU area under curve was predictive for woman and 5-FDHU area under curve for men. CONCLUSION: A population pharmacokinetic mixture model was developed to describe kinetic profiles of 5-FU and its major metabolite. This model has significant implications, to identify patients with potentially low DPD phenotype requiring earlier adjustment of the 5-FU dose. Also this analysis highlights the need for developing alternative dosing-scheme for women.

Effect of fluid loading during hypovolaemic shock on caspofungin pharmacokinetic parameters in pig.

INTRODUCTION: Caspofungin treatment is frequently initiated in shock patients. In the present study, we investigated the influence of hypovolaemic shock requiring fluid loading on the plasma and pulmonary pharmacokinetic parameters of caspofungin in the pig. METHODS: After being anaesthetised and mechanically ventilated, 12 pigs were bled to induce a two-hour deep shock and resuscitated using normal saline based on haemodynamic goals. A one-hour infusion of 70 mg of caspofungin was started at the beginning of the resuscitation period. The lungs were removed four hours after caspofungin administration. Sixteen animals served as controls without haemorrhage. Caspofungin concentrations were measured by using high-performance liquid chromatography, and a two-compartment population pharmacokinetic analysis was performed. RESULTS: In the shock group, the volume of blood removed was 39 ± 7 mL/kg and a volume of 90 ± 17 mL/kg saline was infused throughout the resuscitation period. The extravascular lung water index was higher in the shock group (9.3 ± 1.6 mL/kg vs 5.7 ± 1 mL/kg in the control group; P < 0.01). In the shock group, the median (interquartile range) maximal plasma concentration was 37% lower than in the control group (21.6 µg/mL (20.7 to 22.3) vs 33.1 µg/mL (28.1 to 38.3); P < 0.01). The median area under curve (AUC) from zero to four hours was 25% lower in the shock group than in the control group (60.3 hours × µg/mL (58.4 to 66.4) vs 80.8 hours × µg/mL (78.3 to 96.9); P < 0.01), as was the median lung caspofungin concentration (1.22 µg/g (0.89 to 1.46) vs 1.64 µg/g (1.22 to 2.01); P < 0.01). However, the plasma-to-tissue ratios were not different between the groups, indicating that lung diffusion of caspofungin was not affected after shock followed by fluid loading. Pharmacokinetic analysis showed that the peripheral volume of distribution of caspofungin and intercompartmental clearance were significantly higher in the shock group, as was the total apparent volume of distribution. CONCLUSIONS: Hypovolaemic shock followed by fluid loading in the pig results in a significant increase in the apparent volume of distribution of caspofungin and in a decrease in its plasma and pulmonary exposition. Although our model was associated with capillary leakage and pulmonary oedema, our results should be generalised to the septic shock with caution. Future investigations should focus on monitoring plasma caspofungin concentrations and optimal caspofungin dosing in shock patients.

Validation of an electrospray ionization LC-MS/MS method for quantitative analysis of raltegravir, etravirine, and 9 other antiretroviral agents in human plasma samples.

BACKGROUND: Raltegravir is the first human immunodeficiency virus-1 (HIV-1) integrase inhibitor used in treatment-experienced patients who have evidence of viral replication and HIV-1 strains resistance to multiple antiretroviral regimens. Etravirine is a novel NNRTI, active against HIV-1 strains harboring multiple NNRTI mutations. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of raltegravir, etravirine, and 9 other antiretroviral agents (amprenavir, atazanavir, darunavir, efavirenz, indinavir, lopinavir, ritonavir, saquinavir, and tipranavir) in plasma at the concentrations associated with therapy. MATERIALS AND METHODS: The ritonavir analog, methyl indinavir, and lopinavir-d8 were used as internal standards, added to 100 microL of plasma sample prior to a protein precipitation using methanol. Chromatographic separation was achieved on a C18 HPLC column (Waters Sunfire 100 x 2.1 mm, 3.5 microm) with a mobile phase gradient at a flow rate of 0.3 mL/min. Five microL of sample were injected into the LC-MS/MS system (Waters Quattro Premier XE) to determine concentrations of raltegravir, etravirine, and other antiretroviral agents. RESULTS AND DISCUSSION: This method showed an excellent linearity for all calibration curves (r2 > 0.998). The lower limit of quantification was established at 5 ng/mL for raltegravir and 40 ng/mL for etravirine, with precision and accuracy within +/-20% and 80% to 120% for all analytes. Intraassay and interassay precision and inaccuracy ranged from -9.2% to 6.9% for raltegravir and from -14.3% to 12.3% for etravirine and were less than 15% for all other compounds. No matrix effect was observed for any of the antiretrovirals studied. CONCLUSION: A rapid, specific, and sensitive LC-MS/MS method for quantification of raltegravir, etravirine, and 9 other antiretrovirals in human plasma was developed and was successfully applied for routine therapeutic drug monitoring.