Voriconazole Therapeutic Drug Monitoring Practices in Intensive Care.

BACKGROUND: Routine therapeutic drug monitoring of voriconazole seems to be beneficial. This study investigated the therapeutic drug monitoring practices in intensive care to derive possible recommendations for improvement. METHODS: A retrospective chart review was performed for patients aged ≥18 years who started treatment with voriconazole, which lasted for at least 3 days while being admitted to an intensive care unit to assess possible differences between the patients with and without voriconazole trough concentrations measured. RESULTS: In 64 (76%) of the 84 patients, voriconazole trough concentrations were measured. The groups differed significantly with respect to the duration of voriconazole treatment and intensive care unit admission. Time of sampling was very early and therefore inappropriate for 49% of the first measured voriconazole trough concentrations and in 48% of the subsequent measured concentrations. Of the 349 trough concentrations measured, 129 (37%) were outside the therapeutic window. In 11% of these cases, no recommendation was provided without identifiable reason. In addition, 27% of recommended dose adjustments were not implemented, probably because the advice was not suited for the specific clinical situation. CONCLUSIONS: The performance of voriconazole therapeutic drug monitoring can still be improved although voriconazole concentrations were monitored in most patients. A multidisciplinary approach-for instance by means of antifungal stewardship-will probably be able to overcome problems encountered such as timing of sampling, incompleteness of data in clinical context, and lack of implementation of recommendations.

Subtherapeutic Posaconazole Exposure and Treatment Outcome in Patients With Invasive Fungal Disease.

BACKGROUND: Posaconazole exposure seems to be subtherapeutic in some patients with invasive fungal disease. Due to the pharmacokinetic variability of posaconazole, therapeutic drug monitoring may help to optimize the efficacy of this antifungal drug. METHODS: A retrospective study of patients treated with posaconazole from January 2008 to April 2014 and for whom posaconazole serum concentrations were available was conducted. Risk factors for underexposure of posaconazole were detected, and the relationship between posaconazole exposure and treatment outcome according to the European Organization for Research and Treatment of Cancer (EORTC) criteria was assessed. RESULTS: Seventy patients met the inclusion criteria, 45 patients received posaconazole as treatment, and 25 patients received posaconazole as a prophylactic. Posaconazole serum trough concentrations were <1.25 mg/L in 44.4% of patients receiving treatment and <0.7 mg/L in 40.0% of patients receiving prophylactic posaconazole. Multiple linear regression analysis showed a significant, independent, and negative association of the posaconazole serum trough concentration with a lack of enteral nutrition (P < 0.001), vomiting (P = 0.035), the use of a proton pump inhibitor or H2-receptor antagonist (P < 0.001), a liquid diet (P = 0.002), concomitant chemotherapy (P = 0.004), and a posaconazole dose frequency of 2 times daily (P = 0.015). A higher posaconazole concentration was associated with a better treatment outcome [odds ratio = 22.22 (95% confidence interval, 3.40-145.33); P = 0.001]. CONCLUSIONS: Posaconazole exposure is insufficient in more than 40% of patients at risk of or with invasive fungal disease, and posaconazole exposure is positively correlated with a successful treatment outcome. Therapeutic drug monitoring of posaconazole can detect underexposure and can be helpful in treatment optimization.

Limited-sampling strategies for anidulafungin in critically ill patients.

Efficacy of anidulafungin is driven by the area under the concentration-time curve (AUC)/MIC ratio. Determination of the anidulafungin AUC along with MIC values can therefore be useful. Since obtaining a full concentration-time curve to determine an AUC is not always feasible or appropriate, limited-sampling strategies may be useful in adequately estimating exposure. The objective of this study was to develop a model to predict the individual anidulafungin exposure in critically ill patients using limited-sampling strategies. Pharmacokinetic data were derived from 20 critically ill patients with invasive candidiasis treated with anidulafungin. These data were used to develop a two-compartment model in MW\Pharm using an iterative 2-stage Bayesian procedure. Limited-sampling strategies were subsequently investigated using two methods, a Bayesian analysis and a linear regression analysis. The best possible strategies for these two methods were evaluated by a Bland-Altman analysis for correlation of the predicted and observed AUC from 0 to 24 h (AUC0-24) values. Anidulafungin exposure can be adequately estimated with the concentration from a single sample drawn 12 h after the start of the infusion either by linear regression (R2=0.99; bias, 0.05%; root mean square error [RMSE], 3%) or using a population pharmacokinetic model (R2=0.89; bias, -0.1%; RMSE, 9%) in critically ill patients and also in less severely ill patients, as reflected by healthy volunteers. Limited sampling can be advantageous for future studies evaluating the pharmacokinetics and pharmacodynamics of anidulafungin and for therapeutic drug monitoring in selected patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT01047267.).

Inflammation is associated with voriconazole trough concentrations.

Voriconazole concentrations display a large variability, which cannot completely be explained by known factors. Inflammation may be a contributing factor, as inflammatory stimuli can change the activities and expression levels of cytochrome P450 isoenzymes. We explored the correlation between inflammation, reflected by C-reactive protein (CRP) concentrations, and voriconazole trough concentrations. A retrospective chart review of patients with at least one steady-state voriconazole trough concentration and a CRP concentration measured on the same day was performed. A total of 128 patients were included. A significantly (P < 0.001) higher voriconazole trough concentration was observed in patients with severe inflammation (6.2 mg/liter; interquartile range [IQR], 3.4 to 8.7 mg/liter; n = 20) than in patients with moderate inflammation (3.4 mg/liter; IQR, 1.6 to 5.4 mg/liter; n = 60) and in patients with no to mild inflammation (1.6 mg/liter; IQR, 0.8 to 3.0 mg/liter; n = 48). The patients in all three groups received similar voriconazole doses based on mg/kg body weight (P = 0.368). Linear regression analyses, both unadjusted and adjusted for covariates of gender, age, dose, route of administration, liver enzymes, and interacting coadministered medications, showed a significant association between voriconazole and CRP concentration (P < 0.001). For every 1-mg/liter increase in the CRP concentration, the voriconazole trough concentration increased by 0.015 mg/liter (unadjusted 95% confidence interval [CI], 0.011 to 0.020 mg/liter; adjusted 95% CI, 0.011 to 0.019 mg/liter). Inflammation, reflected by the C-reactive protein concentration, is associated with voriconazole trough concentrations. Further research is necessary to assess if taking the inflammatory status of a patient into account is helpful in therapeutic drug monitoring of voriconazole to maintain concentrations in the therapeutic window, thereby possibly preventing suboptimal treatment or adverse events.

Low but sufficient anidulafungin exposure in critically ill patients.

The efficacy of anidulafungin is driven by the area under the concentration-time curve (AUC)/MIC ratio. Patients in intensive care may be at risk for underexposure. In critically ill patients with an invasive Candida infection, the anidulafungin exposure and a possible correlation with disease severity or plasma protein levels were explored. Concentration-time curves were therefore obtained at steady state. Anidulafungin concentrations were measured with a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The MIC values of the Candida species were determined with the Etest. The target AUC/MIC ratio was based on European Committee on Antimicrobial Susceptibility Testing (EUCAST) data. Twenty patients were included. The patients received a maintenance dose of 100 mg once daily after a loading dose of 200 mg on the first day. The mean (±standard deviation) AUC, maximum concentration of drug in plasma (Cmax), and minimum concentration of drug in plasma (Cmin) were 69.8 ± 24.1 mg · h/liter, 4.7 ± 1.4 mg/liter, and 2.2 ± 0.8 mg/liter, respectively. The MIC values of all cultured Candida species were below the EUCAST MIC breakpoints. The exposure to anidulafungin in relation to the MIC that was determined appeared sufficient in all patients. The anidulafungin exposure was low in our critically ill patients. However, combined with the low MICs of the isolated Candida strains, the lower exposure observed in comparison to the exposure in the general patient population resulted in favorable AUC/MIC ratios, based on EUCAST data. No correlation was observed between anidulafungin exposure and disease severity or plasma protein concentrations. In patients with less-susceptible Candida albicans or glabrata strains, we recommend considering determining the anidulafungin exposure to ensure adequate exposure. (This trial has been registered at ClinicalTrials.gov under registration no. NCT01047267.).

Simultaneous quantification of anidulafungin and caspofungin in plasma by an accurate and simple liquid chromatography tandem mass-spectrometric method.

INTRODUCTION: Echinocandins are a valuable addition for the treatment of invasive fungal infections, as they are efficacious, demonstrate low toxicity, and have limited drug-drug interactions. In specific clinical situations when altered pharmacokinetics can be expected or dosing guidelines are conflicting, it may be useful to measure concentrations. For this purpose, a liquid chromatography tandem mass-spectrometric method to measure anidulafungin and caspofungin in ethylenediaminetetraacetic acid plasma was developed. METHODS: The method was developed on a Thermo Fisher TSQ Quantum LC-MS/MS. For separation, a BetaBasic C4 (100 mm × 3.0 mm; 5 µm) analytical column was used. Sample preparation consisted of protein precipitation directly in the autosampler vial. The internal standard aculeacin A is structurally related, not used in humans, and commercially available. The method was validated according to the guidelines for bioanalytical method validation of the Food and Drug Administration. RESULTS: The method was accurate (bias ranging from -3.0% to 1.9%) and precise (within-run and between-run coefficients of variation of 2.2% to 7.7% and 1.6% to 9.0%, respectively). All calibration curves were linear over a range of 0.5-10.0 mg/L for anidulafungin and 0.1-20.0 mg/L for caspofungin, and if necessary, samples can be diluted 10-fold. The samples were stable for 3 freeze-thaw cycles, with a bias ranging from 0.6% to 11%. The maximum bias from the worst storage condition, 72 hours at room temperature, was -14.7%. In patient samples, anidulafungin peak concentrations ranged from 2.8 to 8.6 mg/L (n = 20) and trough concentrations ranged from 1.0 to 4.7 mg/L (n = 79). The measured caspofungin concentrations ranged from 1.9 to 7.3 mg/L (n = 20). CONCLUSIONS: The method developed has a straightforward sample preparation and uses a structural analog as the internal standard. This method has been applied successfully for the measurement of anidulafungin and caspofungin concentrations in patient samples, both for clinical practice and for research.