The pharmacokinetic profile of voriconazole during continuous high-volume venovenous hemofiltration in a critically ill patient

Renal Replacement Therapy as a New Indicator of Voriconazole Clearance in a Population Pharmacokinetic Analysis of Critically Ill Patients

AIMS

The pharmacokinetic (PK) profiles of voriconazole in intensive care unit (ICU) patients differ from that in other patients. We aimed to develop a population pharmacokinetic (PopPK) model to evaluate the effects of using extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT) and those of various biological covariates on the voriconazole PK profile.

METHODS

Modeling analyses of the PK parameters were conducted using the nonlinear mixed-effects modeling method (NONMEM) with a two-compartment model. Monte Carlo simulations (MCSs) were performed to observe the probability of target attainment (PTA) when receiving CRRT or not under different dosage regimens, different stratifications of quick C-reactive protein (qCRP), and different minimum inhibitory concentration (MIC) ranges.

RESULTS

A total of 408 critically ill patients with 746 voriconazole concentration-time data points were included in this study. A two-compartment population PK model with qCRP, CRRT, creatinine clearance rate (CLCR), platelets (PLT), and prothrombin time (PT) as fixed effects was developed using the NONMEM.

CONCLUSIONS

We found that qCRP, CRRT, CLCR, PLT, and PT affected the voriconazole clearance. The most commonly used clinical regimen of 200 mg q12h was sufficient for the most common sensitive pathogens (MIC ≤ 0.25 mg/L), regardless of whether CRRT was performed and the level of qCRP. When the MIC was 0.5 mg/L, 200 mg q12h was insufficient only when the qCRP was <40 mg/L and CRRT was performed. When the MIC was ≥2 mg/L, a dose of 300 mg q12h could not achieve ≥ 90% PTA, necessitating the evaluation of a higher dose.

A Large Retrospective Assessment of Voriconazole Exposure in Patients Treated with Extracorporeal Membrane Oxygenation

BACKGROUND

Voriconazole is one of the first-line therapies for invasive pulmonary aspergillosis. Drug concentrations might be significantly influenced by the use of extracorporeal membrane oxygenation (ECMO). We aimed to assess the effect of ECMO on voriconazole exposure in a large patient population.

METHODS

Critically ill patients from eight centers in four countries treated with voriconazole during ECMO support were included in this retrospective study. Voriconazole concentrations were collected in a period on ECMO and before/after ECMO treatment. Multivariate analyses were performed to evaluate the effect of ECMO on voriconazole exposure and to assess the impact of possible saturation of the circuit's binding sites over time.

RESULTS

Sixty-nine patients and 337 samples (190 during and 147 before/after ECMO) were analyzed. Subtherapeutic concentrations (<2 mg/L) were observed in 56% of the samples during ECMO and 39% without ECMO (p = 0.80). The median trough concentration, for a similar daily dose, was 2.4 (1.2-4.7) mg/L under ECMO and 2.5 (1.4-3.9) mg/L without ECMO (p = 0.58). Extensive inter-and intrasubject variability were observed. Neither ECMO nor squared day of ECMO (saturation) were retained as significant covariates on voriconazole exposure.

CONCLUSIONS

No significant ECMO-effect was observed on voriconazole exposure. A large proportion of patients had voriconazole subtherapeutic concentrations.

Voriconazole therapeutic drug monitoring in critically ill patients improves efficacy and safety of antifungal therapy

Since voriconazole plasma trough concentration (VPC) is related to its efficacy and adverse events, therapeutic drug monitoring (TDM) is recommended to perform. However, there is no report about the data of voriconazole TDM in critically ill patients in China. This retrospective study was performed to determine whether voriconazole TDM was associated with treatment response and/or voriconazole adverse events in critically ill patients, and to identify the potential risk factors associated with VPC. A total of 216 critically ill patients were included. Patients were divided into two groups: those underwent voriconazole TDM (TDM group, n = 125) or did not undergo TDM (non-TDM group, n = 91). The clinical response and adverse events were recorded and compared. Furthermore, in TDM group, multivariate logistic regression analysis was performed to identify the possible risk factors resulting in the variability in initial VPC. The complete response in the TDM group was significantly higher than that in the non-TDM group (P = .012). The incidence of adverse events strongly associated with voriconazole in the non-TDM group was significantly higher than that in the TDM group (19.8% vs 9.6%; P = .033). The factors, including age (OR 0.934, 95% CI: 0.906-0.964), male (OR 5.929, 95% CI: 1.524-23.062), serum albumin level (OR 1.122, 95% CI: 1.020-1.234), diarrhoea (OR 4.953, 95% CI: 1.495-16.411) and non-intravenous administration (OR 4.763, 95% CI: 1.576-14.39), exerted the greatest effects on subtherapeutic VPC (VPC < 1.5 mg/L) in multivariate analysis. Intravenous administration (OR 7.657, 95% CI: 1.957-29.968) was a significant predictor of supratherapeutic VPC (VPC > 4.0 mg/L). TDM can result in a favourable clinical efficacy and a lower incidence of adverse events strongly associated with voriconazole in critically ill patients. Subtherapeutic VPC was closely related to younger age, male, hyperalbuminaemia, diarrhoea and non-intravenous administration, and intravenous administration was a significant predictor of supratherapeutic VPC.

Pharmacokinetics and Pharmacodynamics of Anti-infective Agents during Continuous Veno-venous Hemofiltration in Critically Ill Patients: Lessons Learned from an Ancillary Study of the IVOIRE Trial

Background

Hemofiltration rate, changes in blood and ultrafiltration flow, and discrepancies between the prescribed and administered doses strongly influence pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial agents during continuous veno-venous hemofiltration (CVVH) in critically ill patients.

Methods

Ancillary data were from the prospective multicenter IVOIRE (hIgh VOlume in Intensive caRE) study. High volume (HV, 70 mL/kg/h) was at random compared with standard volume (SV, 35 mL/kg/h) CVVH in septic shock patients with acute kidney injury (AKI). PK/PD parameters for all antimicrobial agents used in each patient were studied during five days.

Results

Antimicrobial treatment met efficacy targets for both percentage of time above the minimal inhibitory concentration and inhibitory quotient. A significant correlation was observed between the ultrafiltration flow and total systemic clearance (Spearman test: P < 0.005) and between CVVH clearance and drug elimination half-life (Spearman test: P < 0.005). All agents were easily filtered. Mean sieving coefficient ranged from 38.7% to 96.7%. Mean elimination half-life of all agents was significantly shorter during HV-CVVH (from 1.29 to 28.54 h) than during SV-CVVH (from 1.51 to 33.85 h) (P < 0.05).

Conclusions

This study confirms that CVVH influences the PK/PD behavior of most antimicrobial agents. Antimicrobial elimination was directly correlated with convection rate. Current antimicrobial dose recommendations will expose patients to underdosing and increase the risk for treatment failure and development of resistance. Dose recommendations are proposed for some major antibiotic and antifungal treatments in patients receiving at least 25 mL/kg/h CVVH.

Considerations for Medication Management and Anticoagulation During Continuous Renal Replacement Therapy

Providing safe and high-quality care to critically ill patients receiving continuous renal replacement therapy (CRRT) includes adequate drug dosing and evaluation of patients' response to medications during therapy. Pharmacokinetic drug studies in acute kidney injury and CRRT are limited, considering the number of medications used in critical care. Therefore, it is important to understand the basic principles of drug clearance during CRRT by evaluating drug properties, CRRT modalities, and how they affect medication clearance. Few published studies have addressed drug disposition and clinical response during CRRT. Additionally, clotting in the CRRT circuit is a concern, so a few options for anticoagulation strategies are presented. This article reviews (1) the CRRT system and drug property factors that affect medication management, (2) the evidence available to guide drug dosing, and (3) anticoagulation strategies for critically ill patients receiving CRRT.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Quality of pharmacokinetic studies in critically ill patients receiving continuous renal replacement therapy

Continuous renal replacement therapy (CRRT) is the preferred renal replacement therapy modality in the critically ill. We aimed to reveal the literature on the pharmacokinetic studies in critically ill patients receiving CRRT with special reference to quality assessment of these studies and the CRRT dose. We conducted a systematic review by searching the MEDLINE, EMBASE, and the Cochrane databases to December 2009 and bibliographies of relevant review articles. We included original studies reporting from critically ill adult subjects receiving CRRT because of acute kidney injury with a special emphasis on drug pharmacokinetics. We used the minimum reporting criteria for CRRT studies by Acute Dialysis Quality Initiative (ADQI) and, second, the Downs and Black checklist to assess the quality of the studies. We calculated the CRRT dose per study. We included pharmacokinetic parameters, residual renal function, and recommendations on drug dosing. Of 182 publications, 95 were considered relevant and 49 met the inclusion criteria. The median [interquartile range (IQR)] number of reported criteria by ADQI was 7.0 (5.0-8.0) of 12. The median (IQR) Downs and Black quality score was 15 (14-16) of 32. None of the publications reported CRRT dose directly. The median (IQR) weighted CRRT dose was 23.7 (18.8-27.9) ml/kg/h. More attention should be paid both to standardizing the CRRT dose and reporting of the CRRT parameters in pharmacokinetic studies. The general quality of the studies during CRRT in the critically ill was only moderate and would be greatly improved by reports in concordant with the ADQI recommendations.

Pharmacokinetic evaluation of voriconazole treatment in critically ill patients undergoing continuous venovenous hemofiltration

INTRODUCTION

Voriconazole represents an essential part of antimicrobial therapy in critically ill patients. The aim of this study was to exclude a significant alteration in voriconazole pharmacokinetics in critically ill patients undergoing continuous venovenous hemofiltration (CVVH).

METHODS

Six patients dependent on CVVH with evidence of an invasive mycotic infection treated with intravenous voriconazole at the standard dosing regimen were investigated. The total serum concentration of voriconazole in arterial blood and the concentration in ultrafiltrate were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection. The authors profiled a 5-point pharmacokinetic concentration-time curve during the 12-hour standard maintenance dosing interval and derived the basic pharmacokinetic parameters.

RESULTS

The serum voriconazole concentration did not decrease <1.0 mg/L at any time point, and the mean was 4.3 ± 2.6 mg/L and the median (range) 3.6 (9.0) mg/L. The sieving coefficient of the drug did not exceed 0.30 in any patient (0.22 ± 0.08). The mean serum AUC0-12, the mean total clearance, and the mean clearance via CVVH were 53.52 ± 29.97 mg·h/L [the median (range) of 57.74 (62.34) mg·h/L], 0.11 ± 0.07 L·h-1·kg-1, and 0.007 ± 0.003 L·h-1·kg-1, respectively. The clearance by the CVVH method ranged from 4% to 20% of the total drug clearance. The disposition of voriconazole was not compromised. The mean elimination half-life was 27.58 ± 35.82 hours [the median of 13.10 (92.21) hours], and the mean distribution volume value was 3.28 ± 3.10 L/kg [the median of 2.01 (8.10) L/kg]. Marked variability in serum concentrations, elimination half-life, distribution volume, and total clearance was seen. Half of the patients showed some drug accumulation.

CONCLUSIONS

The clearance of voriconazole by CVVH is not clinically significant. In view of this finding, voriconazole dose adjustment in patients undergoing the standard method of CVVH is not required. However, the observed potential for an unpredictable voriconazole accumulation suggests the usefulness for monitoring its levels in critically ill patients.

Using pharmacokinetics and pharmacodynamics to optimise dosing of antifungal agents in critically ill patients: a systematic review

The prevalence of invasive fungal infections (IFIs) caused by Candida spp. is increasing in critically ill patients. Recent development of new antifungal agents has significantly contributed to the successful treatment of IFIs. However, the pharmacokinetics of antifungal agents can be altered in a number of disease states, including critical illness. Therefore, doses established in healthy volunteers and other patient groups may not be appropriate for the critically ill. Moreover, inadequate dosing may contribute to treatment failure and the emergence of resistance. This systematic review provides a critical analysis of the pharmacokinetics of antifungal agents in the critically ill and their relevance to dosing requirements in clinical practice. Based on the limited data available, dosing of some antifungal agents may have to be adjusted in critically ill patients with conserved renal function as well as in those requiring renal replacement therapy. Further research to confirm the appropriateness of current dosing strategies to attain the appropriate pharmacodynamic targets is recommended.

Effects of high-volume hemofiltration on alveolar-arterial oxygen exchange in patients with refractory septic shock

BACKGROUND

High-volume hemofiltration (HVHF) is technically possible in severe acute pancreatitis (SAP) patients complicated with multiple organ dysfunction syndrome (MODS). Continuous HVHF is expected to become a beneficial adjunct therapy for SAP complicated with MODS. In this study, we aimed to explore the effects of fluid resuscitation and HVHF on alveolar-arterial oxygen exchange, the Acute Physiology and Chronic Health Evaluation II (APACHE II) score in patients with refractory septic shock.

METHODS

A total of 89 refractory septic shock patients, who were admitted to ICU, the Provincial Hospital affiliated to Shandong University from August 2006 to December 2009, were enrolled in this retrospective study. The patients were randomly divided into two groups: fluid resuscitation (group A, n=41), and fluid resuscitation plus high-volume hemofiltration (group B, n=48). The levels of O2 content of central venous blood (CcvO2), arterial oxygen content (CaO2), alveolar-arterial oxygen pressure difference P(A-a)DO2, ratio of arterial oxygen pressure/alveolar oxygen pressure (PaO2/PaO2), respiratory index (RI) and oxygenation index (OI) were determined. The oxygen exchange levels of the two groups were examined based on the arterial blood gas analysis at different times (0, 24, 72 hours and 7 days of treatment) in the two groups. The APACHE II score was calculated before and after 7-day treatment in the two groups.

RESULTS

The levels of CcvO2, CaO2 on day 7 in group A were significantly lower than those in group B (CcvO2: 0.60±0.24 vs. 0.72±0.28, P<0.05; CaO2: 0.84±0.43 vs. 0.94±0.46, P<0.05). The level of oxygen extraction rate (O2ER) in group A on the 7th day was significantly higher than that in group B (28.7±2.4 vs. 21.7±3.4, P<0.01). The levels of P(A-a)DO2 and RI in group B on the 7th day were significantly lower than those in group A. The levels of PaO2/PaO2 and OI in group B on 7th day were significantly higher than those in group A (P<0.05 or P<0.01). The APACHE II score in the two groups reduced gradually after 7-day treatment, and the APACHE II score on the 7th day in group B was significantly lower than that in group A (8.2±3.8 vs. 17.2±6.8, P<0.01).

CONCLUSION

HVHF combined with fluid resuscitation can improve alveolar-arterial-oxygen exchange, decrease the APACHE II score in patients with refractory septic shock, and thus it increases the survival rate of patients.

Development and validation of an efficient HPLC method for quantification of voriconazole in plasma and microdialysate reflecting an important target site

Voriconazole is a very potent antifungal agent used to treat serious fungal infections (candidiasis); it is also the therapy of choice for aspergillosis. After standard dosing, several factors affect exposure of voriconazole, resulting in large variability and demanding further elucidation of drug distribution. For measurements at the site of action, microdialysis is considered to be an outstanding minimally invasive method. For determination of voriconazole in microdialysate and human plasma a new, efficient, reliable, and robust HPLC assay using UV detection at 254 nm has been developed and validated. After simple sample preparation using acetonitrile for plasma and for microdialysate, 20 microL were injected and separated on an RP-18 column. The chromatographic run time was less than 4 min. Overall, the assay showed high precision (CV 93.9 to 99.5%) and accuracy (RE -96.7 to +107%) for both matrices. Of the 36 drug products typically co-administered with voriconazole, none except ambroxol interfered with its peak signal, and this interference was successfully managed. In summary, the method is highly suitable for application in (pre)clinical microdialysis studies, e.g., of critically ill patients with invasive mycoses.