Bioavailability of voriconazole in hospitalised patients

An important element in antimicrobial stewardship programmes is early switch from intravenous (i.v.) to oral antimicrobial treatment, especially for highly bioavailable drugs. The antifungal agent voriconazole is available both in i.v. and oral formulations and bioavailability is estimated to be >90% in healthy volunteers, making this drug a suitable candidate for such a transition. Recently, two studies have shown that the bioavailability of voriconazole is substantially lower in patients. However, for both studies various factors that could influence the voriconazole serum concentration, such as inflammation, concomitant intake of food with oral voriconazole, and gastrointestinal complications, were not included in the evaluation. Therefore, in this study a retrospective chart review was performed in adult patients treated with both oral and i.v. voriconazole at the same dose and within a limited (≤5 days) time interval in order to evaluate the effect of switching the route of administration on voriconazole serum concentrations. A total of 13 patients were included. The mean voriconazole trough concentration was 2.28 mg/L [95% confidence interval (CI) 1.29-3.26 mg/L] for i.v. voriconazole administration and 2.04 mg/L (95% CI 0.78-3.30 mg/L) for oral administration. No significant difference was found in the mean oral and i.v. trough concentrations of voriconazole (P = 0.390). The mean bioavailability was 83.0% (95% CI 59.0-107.0%). These findings suggest that factors other than bioavailability may cause the observed difference in voriconazole trough concentrations between oral and i.v. administration in the earlier studies and stress the need for an antimicrobial stewardship team to guide voriconazole dosing.

Voriconazole metabolism is influenced by severe inflammation: a prospective study

BACKGROUND

During an infection or inflammation, several drug-metabolizing enzymes in the liver are down-regulated, including cytochrome P450 iso-enzymes. Since voriconazole is extensively metabolized by cytochrome P450 iso-enzymes, the metabolism of voriconazole can be influenced during inflammation via reduced clearance of the drug, resulting in higher voriconazole trough concentrations.

OBJECTIVE

To investigate prospectively the influence of inflammation on voriconazole metabolism and voriconazole trough concentrations.

METHODS

A prospective observational study was performed at the University Medical Center Groningen. Patients were eligible for inclusion if they were ≥18 years old and treated with voriconazole. Voriconazole and voriconazole-N-oxide concentrations were determined in discarded blood samples. To determine the degree of inflammation, C-reactive protein (CRP) concentrations were used. Subsequently, a longitudinal data analysis was performed to assess the effect of inflammation on the metabolic ratio and voriconazole trough concentration.

RESULTS

Thirty-four patients were included. In total 489 voriconazole trough concentrations were included in the longitudinal data analysis. This analysis showed that inflammation, reflected by CRP concentrations, significantly influenced the metabolic ratio, voriconazole trough concentration and voriconazole-N-oxide concentration (all P < 0.001), when corrected for other factors that could influence voriconazole metabolism. The metabolic ratio was decreased by 0.99229^N and the voriconazole-N-oxide concentration by 0.99775^N, while the voriconazole trough concentration was increased by 1.005321^N, where N is the difference in CRP units (in mg/L).

CONCLUSIONS

This study shows that voriconazole metabolism is decreased during inflammation, resulting in higher voriconazole trough concentrations. Therefore, frequent monitoring of voriconazole serum concentrations is recommended during and following severe inflammation.

A retrospective analysis of patient-specific factors on voriconazole clearance

Background

Voriconazole concentrations display a large variability, which cannot completely be explained by known factors. We investigated the relationships of voriconazole concentration with patient-specific variables and concomitant medication to identify clinical factors affecting voriconazole clearance.

Methods

A retrospective chart review of voriconazole trough concentration, laboratory data, and concomitant medication in patients was performed. The concentration/dose ratio (C/D-ratio) was assessed as a surrogate marker of total clearance by dividing voriconazole concentration by daily dose per kg of body weight.

Results

A total of 77 samples from 63 patients were obtained. In multiple linear regression analysis, increased C-reactive protein (CRP) level (p < 0.05) and decreased albumin (Alb) level (p < 0.05) were associated with significantly increased C/D-ratio of voriconazole, and coadministration with a glucocorticoid was associated with significantly (p < 0.05) decreased C/D-ratio of voriconazole (adjusted r² = 0.31). Regarding CRP and Alb, receiver operating characteristic curve analysis indicated that increased CRP level and decreased Alb level were significant predictors of toxic trough concentration of voriconazole. For CRP, area under the curve (AUC) and cutoff value were 0.71 (95 % confidence interval (CI), 0.57–0.86, p < 0.01) and 4.7 mg/dl, respectively. For Alb, AUC and cutoff value were 0.68 (95 % CI, 0.53–0.82, p < 0.05) and 2.7 g/dl, respectively. A significant difference was seen in voriconazole trough concentration between patients with hepatotoxicity and those without (5.69 μg/ml vs 3.0 μg/ml, p < 0.001).

Conclusion

Coadministration of glucocorticoid and inflammation, reflected by elevated CRP level and hypoalbuminemia, are associated with voriconazole clearance. We propose that early measurement of voriconazole concentration before the plateau phase will lead to avoidance of a toxic voriconazole level in patients with elevated CRP level and hypoalbuminemia, although further studies are needed to confirm our findings.

Impact of cytochrome P450 2C19 polymorphisms on the pharmacokinetics of tacrolimus when coadministered with voriconazole

This study evaluated the effects of cytochrome P450 (CYP) 2C19 polymorphisms on tacrolimus pharmacokinetics when coadministered with voriconazole. Eighteen healthy volunteers, including 6 individuals in each CYP2C19 genotype (extensive metabolizers [EMs], intermediate metabolizers [IMs], and poor metabolizers [PMs]), received a single oral dose of 3 mg tacrolimus alone or in combination with 200 mg voriconazole twice daily at steady state. When tacrolimus was coadministered with voriconazole, a significant increase in area under its concentration‐time curve (AUC_0‐24) was observed for all genotypes. AUC_0‐12 of voriconazole in IMs and PMs were significantly higher than that in EMs (P < .05 and P < .01, respectively). Consequently, AUC_0‐24 of tacrolimus in combination with voriconazole in IMs and PMs were also significantly higher than that in EMs (P < .05). These results demonstrate that CYP2C19 genotypes influenced the exposure of tacrolimus when coadministered with voriconazole, although tacrolimus is mainly metabolized by CYP3A.

Optimizing azole antifungal therapy in the prophylaxis and treatment of fungal infections

PURPOSE OF REVIEW

Azole antifungals are widely used in the prophylaxis and treatment of fungal infections, but are associated with a range of pharmacokinetic challenges and safety issues that necessitate individualized therapy to achieve optimal clinical outcomes. Recent advances in our knowledge of azole exposure-response relationships, therapeutic drug monitoring and individualized dosing strategies are reviewed as follows.

RECENT FINDINGS

Recent studies have significantly improved the understanding of exposure-response relationships for efficacy and toxicity, increasing confidence in target exposure ranges for azole antifungal agents. Population pharmacokinetic modelling of voriconazole has led to studies demonstrating the feasibility of model-guided dose individualization strategies with the drug, which holds significant promise for optimizing therapy. The recent approval of a solid oral tablet formulation of posaconazole with improved bioavailability and once-daily dosing has significantly improved the clinical utility of this agent. Further clinical experience with the investigational azole isavuconazole is needed to determine the role of individualized therapy.

SUMMARY

The coordination of CYP2C19 pharmacogenomic testing with model-guided dose individualization holds significant promise for optimizing therapy with voriconazole. Pharmacokinetic challenges with itraconazole, voriconazole and posaconazole oral suspension continue to require therapeutic drug monitoring to individualize therapy and optimize treatment outcomes.

A pharmacokinetic comparison of two voriconazole formulations and the effect of CYP2C19 polymorphism on their pharmacokinetic profiles

Purpose

SYP-1018 is a lyophilized polymeric nanoparticle formulation of voriconazole that is under development for intravenous dosing. This study compared the pharmacokinetic and tolerability profiles of SYP-1018 with those of Vfend^®, the marketed formulation of voriconazole. The effect of CYP2C19 polymorphism on the voriconazole pharmacokinetics was also evaluated.

Methods

An open-label, two-treatment, two-period, two-sequence crossover study was conducted in 52 healthy male volunteers, who randomly received a single intravenous infusion of either of the two voriconazole formulations at 200 mg. Blood samples were collected up to 24 hours after drug administration for pharmacokinetic analysis. The plasma concentrations of voriconazole were determined using liquid chromatography with tandem mass spectrometry, and the pharmacokinetic parameters were estimated using a noncompartmental method. CYP2C19 genotype was identified in 51 subjects.

Results

The geometric mean ratio (90% confidence interval) of SYP-1018 to Vfend^® was 0.99 (0.93–1.04) for the maximum plasma concentrations (C_max) and 0.97 (0.92–1.01) for the area under the concentration–time curve (AUC) from dosing to the last quantifiable concentration (AUC_last). Nineteen homozygous extensive metabolizers (EMs, *1/*1), 19 intermediate metabolizers (IMs, *1/*2 or *1/*3), and ten poor metabolizers (PMs, *2/*2, *2/*3, or *3/*3) were identified, and the pharmacokinetic comparability between SYP-1018 and Vfend^® was also noted when analyzed separately by genotype. The systemic exposure to voriconazole was greatest in the PM group, followed by the IM, and then the EM groups. Furthermore, the intrasubject variability for C_max and AUC_last was greater in IMs and PMs than in EMs. No serious adverse event occurred, and both treatments were well tolerated.

Conclusion

SYP-1018 had comparable pharmacokinetic and tolerability profiles to Vfend^® after a single intravenous infusion. CYP2C19 genotype affected not only the pharmacokinetics of voriconazole, but its intrasubject variability. SYP-1018 can be further developed as a clinically effective alternative to Vfend^®.

Therapeutic Drug Monitoring and Genotypic Screening in the Clinical Use of Voriconazole

Voriconazole is an antifungal triazole that is the first line agent for treatment of invasive aspergillosis. It is metabolized by CYP2C19, CYP2C9, and CYP3A4 and demonstrates wide interpatient variability in serum concentrations. Polymorphisms in CYP2C19 contribute to variability in voriconazole pharmacokinetics. Here, evidence is examined for the use of voriconazole therapeutic drug monitoring (TDM) and the role of CYP2C19 genotyping in voriconazole dosing. The majority of studies exploring the impact of voriconazole TDM on efficacy and safety have found TDM to be beneficial. However, most of these studies are observational, with only one being a randomized controlled trial. High-volume multicenter randomized controlled trials of TDM are currently not available to support definitive guidelines. There is a significant relationship in healthy volunteers between CYP2C19 genotype and voriconazole pharmacokinetics, but this association is markedly less visible in actual patients. While CYP2C19 genotype data may explain variability of voriconazole serum levels, they alone are not sufficient to guide initial dosing. The timeliness of availability of CYP2C19 genotype data in treatment of individual patients also remains challenging. Additional studies are needed before implementation of CYP2C19 genotyping for voriconazole dosing into routine clinical care.

Therapeutic drug monitoring for triazoles: A needs assessment review and recommendations from a Canadian perspective

Invasive fungal infections cause significant morbidity and mortality in patients with concomitant underlying immunosuppressive diseases. The recent addition of new triazoles to the antifungal armamentarium has allowed for extended-spectrum activity and flexibility of administration. Over the years, clinical use has raised concerns about the degree of drug exposure following standard approved drug dosing, questioning the need for therapeutic drug monitoring (TDM). Accordingly, the present guidelines focus on TDM of triazole antifungal agents. A review of the rationale for triazole TDM, the targeted patient populations and available laboratory methods, as well as practical recommendations based on current evidence from an extended literature review are provided in the present document.

Treatment principles for the management of mold infections

Survival rates among immunocompromised patients with invasive mold infections have markedly improved over the last decade with earlier diagnosis and new antifungal treatment options. Yet, increasing antifungal resistance, breakthrough infections with intrinsically resistant fungi, and potentially life-threatening adverse effects and drug interactions are becoming more problematic, especially with prolonged therapy. Evidence-based recommendations for treating invasive aspergillosis and mucormycosis provide excellent guidance on the initial workup and treatment of these molds, but they cannot address all of the key management issues. Herein, we discuss 10 general treatment principles in the management of invasive mold disease in immunocompromised patients and discuss how these principles can be integrated to develop an effective, individualized treatment plan.

Emerging roles for pharmacists in clinical implementation of pharmacogenomics

Pharmacists are uniquely qualified to play essential roles in the clinical implementation of pharmacogenomics. However, specific responsibilities and resources needed for these roles have not been defined. We describe roles for pharmacists that emerged in the clinical implementation of genotype-guided clopidogrel therapy in the University of Florida Health Personalized Medicine Program, summarize preliminary program results, and discuss education, training, and resources needed to support such programs. Planning for University of Florida Health Personalized Medicine Program began in summer 2011 under leadership of a pharmacist, with clinical launch in June 2012 of a clopidogrel-CYP2C19 pilot project aimed at tailoring antiplatelet therapies for patients undergoing percutaneous coronary intervention and stent placement. More than 1000 patients were genotyped in the pilot project in year 1. Essential pharmacist roles and responsibilities that developed and/or emerged required expertise in pharmacy informatics (development of clinical decision support in the electronic medical record), medication safety, medication-use policies and processes, development of group and individual educational strategies, literature analysis, drug information, database management, patient care in targeted areas, logistical issues in genetic testing and follow-up, research and ethical issues, and clinical precepting. In the first 2 years of the program (1 year planning and 1 year postimplementation), a total of 14 different pharmacists were directly and indirectly involved, with effort levels ranging from a few hours per month, to 25-30% effort for the director and associate director, to nearly full-time for residents. Clinical pharmacists are well positioned to implement clinical pharmacogenomics programs, with expertise in pharmacokinetics, pharmacogenomics, informatics, and patient care. Education, training, and practice-based resources are needed to support these roles and to facilitate the development of financially sustainable pharmacist-led clinical pharmacogenomics practice models.

Therapeutic drug monitoring of voriconazole: a case report of multiple drug interactions in a patient with an increased CYP2C19 activity

Background

Voriconazole is metabolized by cytochrome P450 (CYP) 2C19 and CYP 3A4. Drug-drug interactions and genetic polymorphisms modulate their activities.

Case presentation

A 35-year old African female patient with resistant HIV and a cerebral mass of unknown origin was treated with voriconazole for a suspicion of disseminated Aspergillosis infection. Voriconazole trough concentrations (C₀) were within target range while the patient was under esomeprazole, a CYP2C19 inhibitor. Phenotyping showed decreased CYP2C19 activity, whereas genotyping showed a variant allele associated with increased enzyme activity. The patient was switched to ranitidine because of the introduction of atazanavir. CYP3A4 inhibition by atazanavir combined with uninhibited CYP2C19 activity resulted in subtherapeutic voriconazole C_0. The reintroduction of esomeprazole allowed restoring voriconazole C₀ back to target range.

Conclusion

The integration of drug-drug interactions and pharmacogenetics data is crucial to interpret drug concentrations correctly, thus preventing suboptimal exposure to voriconazole.

How to manage aspergillosis in non-neutropenic intensive care unit patients

Invasive aspergillosis has been mainly reported among immunocompromised patients during prolonged periods of neutropenia. Recently, however, non-neutropenic patients in the ICU population have shown an increasing risk profile for aspergillosis. Associations with chronic obstructive pulmonary disease and corticosteroid therapy have been frequently documented in this cohort. Difficulties in achieving a timely diagnosis of aspergillosis in non-neutropenic patients is related to the non-specificity of symptoms and to lower yields with microbiological tests compared to neutropenic patients. Since high mortality rates are typical of invasive aspergillosis in critically ill patients, a high level of suspicion and prompt initiation of adequate antifungal treatment are mandatory. Epidemiology, risk factors, diagnostic algorithms, and different approaches in antifungal therapy for invasive aspergillosis in non-neutropenic patients are reviewed.

Voriconazole pharmacokinetics and exposure-response relationships: assessing the links between exposure, efficacy and toxicity

The triazole antifungal voriconazole (VCZ) exhibits broad-spectrum antifungal activity and is the first-line treatment for invasive aspergillosis. Highly variable, non-linear pharmacokinetics, metabolism via the polymorphic drug-metabolising enzyme CYP2C19, and a range of serious adverse events (AEs) including hepatotoxicity and neurotoxicity complicate the clinical utility of VCZ. As interest in optimising VCZ treatment has increased, a growing number of studies have examined the relationships between VCZ exposure and efficacy in the treatment and prevention of invasive fungal infections, as well as associations with VCZ-related AEs. This review provides a critical analysis of VCZ pharmacokinetics and exposure-response (E-R) relationships, assessing the links between VCZ exposure, efficacy and toxicity. Low VCZ exposure has frequently been associated with a higher incidence of treatment failure; fewer studies have addressed E-R relationships with prophylactic VCZ. VCZ-related neurotoxicity appears common at high VCZ concentrations and can be minimised by maintaining concentrations below the recommended upper concentration thresholds; hepatotoxicity appears to be associated with increased VCZ exposure but is also prevalent at low concentrations. Further research should aim to inform and optimise the narrow therapeutic range of VCZ as well as develop interventions to individualise VCZ dosing to achieve maximal efficacy with minimal toxicity.

CYP2C19 polymorphisms and therapeutic drug monitoring of voriconazole: are we ready for clinical implementation of pharmacogenomics?

Since its approval by the U.S. Food and Drug Administration in 2002, voriconazole has become a key component in the successful treatment of many invasive fungal infections including the most common, aspergillosis and candidiasis. Despite voriconazole's widespread use, optimizing its treatment in an individual can be challenging due to significant interpatient variability in plasma concentrations of the drug. Variability is due to nonlinear pharmacokinetics and the influence of patient characteristics such as age, sex, weight, liver disease, and genetic polymorphisms in the cytochrome P450 2C19 gene (CYP2C19) encoding for the CYP2C19 enzyme, the primary enzyme responsible for metabolism of voriconazole. CYP2C19 polymorphisms account for the largest portion of variability in voriconazole exposure, posing significant difficulty to clinicians in targeting therapeutic concentrations. In this review, we discuss the role of CYP2C19 polymorphisms and their influence on voriconazole's pharmacokinetics, adverse effects, and clinical efficacy. Given the association between CYP2C19 genotype and voriconazole concentrations, as well as the association between voriconazole concentrations and clinical outcomes, particularly efficacy, it seems reasonable to suggest a potential role for CYP2C19 genotype to guide initial voriconazole dose selection followed by therapeutic drug monitoring to increase the probability of achieving efficacy while avoiding toxicity.

Voriconazole serum concentrations in obese and overweight immunocompromised patients: a retrospective review

STUDY OBJECTIVE

To evaluate the relationship between voriconazole dose and corresponding serum concentrations in obese and overweight immunocompromised patients.

DESIGN

Retrospective medical record review.

SETTING

National Cancer Institute-designated comprehensive cancer center.

PATIENTS

A total of 92 patients with hematologic malignancies and/or hematopoietic stem cell transplants who received voriconazole and had reported steady-state serum concentrations (peak, random, or trough) during 2005-2010; 124 serum concentrations were available for analysis.

MEASUREMENTS AND MAIN RESULTS

Data on patient demographics, voriconazole concentrations, and other clinical and safety data were collected. Patients were stratified based on body mass index (BMI). Patients with higher BMIs tended to have significantly higher median random voriconazole concentrations with intravenous administration (6.4 mg/L for BMI ≥ 25 kg/m(2) vs 2.8 mg/L for BMI < 25 kg/m(2), p=0.04). This trend was more notable with the intravenous than the oral formulations. With the oral formulation, patients with a BMI of 25 kg/m(2) or greater had a median random concentration of 2.8 mg/L compared with 2.0 mg/L in patients with a BMI less than 25 kg/m(2) (p=0.18). Patients with a BMI of 25 kg/m(2) or greater also had a higher median daily voriconazole dose (640 vs 400 mg, p<0.001). No significant differences were noted in factors that would affect oral absorption of voriconazole (e.g., graft-versus-host disease) among BMI groups. When comparing all voriconazole concentrations, higher concentrations were associated with a greater percentage of patients who had alanine aminotransferase levels of more than 3 times the upper limit of normal. Patients with voriconazole random concentrations of 2 mg/L or greater had higher response rates (50%) than patients with concentrations lower than 2 mg/L (33%).

CONCLUSION

Standard voriconazole dosing using actual body weight in obese and overweight patients resulted in higher associated serum concentrations. Dosing using adjusted body weight may be necessary in this population in order to achieve optimal concentrations while preventing the potential for increased toxicity.

Steady-state pharmacokinetics of oral voriconazole and its primary metabolite, N-oxide voriconazole, pre- and post-autologous peripheral stem cell transplantation

Voriconazole (VCZ) is frequently utilized for prevention and treatment of invasive fungal infections in peripheral stem cell transplant (PSCT) patients. We performed an open-label pharmacokinetic study to compare VCZ and N-oxide voriconazole (N-oxide VCZ) pharmacokinetics in patients pre- and post-PSCT. Ten patients completed both sampling periods. The pharmacokinetics of VCZ were unchanged; however, those of N-oxide VCZ were significantly different pre- and post-PSCT.

Pharmacokinetics of intravenous voriconazole in obese patients: implications of CYP2C19 homozygous poor metabolizer genotype

There is a paucity of pharmacokinetic studies describing weight-based dosing of intravenous voriconazole in obese patients. In this case report, we describe the pharmacokinetics of intravenous voriconazole in an obese CYP2C19 homozygous poor metabolizer and review previously reported data regarding the use of intravenous voriconazole in obese patients. A 17-year-old obese Hispanic male patient (body mass index 35 kg/m(2) ) received intravenous voriconazole for the treatment of suspected aspergillosis. After 2.5 days of voriconazole 4 mg/kg intravenously every 12 hours based on adjusted body weight, the voriconazole area under the serum concentration-time curve over the course of a single (12-hr) dosing interval and trough concentration were 86,100 ng · hr/ml and 6.2 µg/ml, respectively. Six days later, the voriconazole dosage was decreased. A trough concentration measured just before the dosage reduction (after 8.5 days of voriconazole 4 mg/kg intravenously every 12 hours based on adjusted body weight) remained elevated at 5.8 µg/ml. Genotyping revealed a CYP2C19 homozygous poor metabolizer (CYP2C19*2/*2). Voriconazole was subsequently discontinued due to QTc prolongation. These data and those from two recent publications suggest that voriconazole does not distribute extensively into human adipose tissue and that obese patients should be dosed on an adjusted body weight basis. If an obese patient dosed on total body weight is also a CYP2C19 poor metabolizer, serum voriconazole concentrations will be further elevated, potentially leading to drug-induced toxicity.

The effect of therapeutic drug monitoring on safety and efficacy of voriconazole in invasive fungal infections: a randomized controlled trial

BACKGROUND

Blood levels of voriconazole, a first line therapy for invasive aspergillosis, may correlate with adverse events and treatment response. However, no randomized controlled studies have been conducted to evaluate the clinical utility of routine therapeutic drug monitoring (TDM) of voriconazole. This study aimed to determine whether routine TDM of voriconazole reduces drug adverse events or improves treatment response in invasive fungal infections.

METHODS

This was a randomized, assessor-blinded, controlled, single center trial. One hundred ten adult patients were randomly assigned to TDM or non-TDM groups. In the TDM group, voriconazole dosage was adjusted (target range, 1.0-5.5 mg/L) according to the serum trough level measured on the fourth day after initiation of voriconazole. The non-TDM group received a fixed, standard dosage. Voriconazole-related adverse events were monitored, and treatment response was assessed three months after the initiation of therapy.

RESULTS

Baseline characteristics including the CYP2C19 genotype were comparable between the two groups. While the incidence of adverse events was not different between the TDM group and the non-TDM group (both 42%; P = .97), the proportion of voriconazole discontinuation due to adverse events was significantly lower in the TDM group than in the non-TDM group (4% vs 17%; P = .02). A complete or partial response was observed in 81% (30 of 37) of patients in the TDM group compared to 57% (20 of 34) in the non-TDM group (P = .04).

CONCLUSIONS

Routine TDM of voriconazole may reduce drug discontinuation due to adverse events and improve the treatment response in invasive fungal infections.

CLINICAL TRIAL REGISTRATION

NCT00890708.

Monitoring trough voriconazole plasma concentrations in haematological patients: real life multicentre experience

The objective of this retrospective study was to evaluate results from voriconazole therapeutic drug monitoring (TDM) in haematological patients in routine clinical practice. Between 2005 and 2010, 1228 blood samples were obtained from 264 haematological patients (median 3 samples/patient; range 1-27) receiving voriconazole for targeted/preemptive treatment of invasive aspergillosis (IA) (46.3% of samples), empirical therapy (12.9%) or prophylaxis (40.8%). A high-pressure liquid chromatography assay was used to analyse voriconazole concentrations. Clinical and laboratory data were analysed retrospectively. The median of the detected voriconazole plasma concentration was 1.00 μg ml(-1) (range <0.20-13.47 μg ml(-1)). Significant inter- and intra-patients variability of measured concentrations (81.9% and 50.5%) were identified. With the exception of omeprazole administration, there was no relevant relationship between measured voriconazole concentrations and drug dose, route administration, age, gender, CYP2C19*2 genotype, gastrointestinal tract abnormality, administration via nasogastric tube, serum creatinine, and liver enzymes. However, per patient analysis identified significant role of individual voriconazole dose and drug form change on measured plasma concentration. Measured voriconazole concentrations did not correlate with the treatment outcome of patients with IA. We only identified a limited number of adverse events related to voriconazole therapy; however, the median plasma concentration was not different from concentrations measured in samples without reported toxicity. Our retrospective study has suggested that routine monitoring of voriconazole plasma concentrations has probably only a limited role in daily haematological practice.

Use of antifungal drugs in hematology

Invasive fungal disease represents a major complication in hematological patients. Antifungal agents are frequently used in hematologic patients for different purposes. In neutropenic patients, antifungal agents may be used as prophylaxis, as empiric or preemptive therapy, or to treat an invasive fungal disease that has been diagnosed. The hematologist must be familiar with the epidemiology, diagnostic tools and strategies of antifungal use, as well as the pharmacologic proprieties of the different antifungal agents. In this paper the principal antifungal agents used in hematologic patients will be discussed as will the clinical scenarios where these agents have been used.