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

Treatment outcomes in patients with proven/probable vs possible invasive mould disease in a phase III trial comparing isavuconazole vs voriconazole

Treatment outcomes in patients with proven/probable vs possible invasive mould disease (IMD; 2008 European Organisation for Research and Treatment of Cancer/Mycoses Study Group [EORTC/MSG] criteria) needed further assessment. The Phase III SECURE trial compared isavuconazole vs voriconazole for treatment of IMD. This post hoc analysis assessed all-cause mortality (ACM) through day 42 (primary endpoint) and day 84, overall and clinical success at end of treatment (EOT), and drug-related treatment-emergent adverse events (TEAEs) in subgroups with proven/probable or possible IMD. Of 516 randomised patients, 304 (58.9%) had proven/probable IMD and 164 (31.8%) had possible IMD as per EORTC/MSG criteria; 48 did not have IMD. Across treatment groups, day 42 and day 84 ACM were numerically lower for possible vs proven/probable IMD (day 42: 17.1% vs 21.1%; P = 0.3, day 84: 26.2% vs 32.6%; P = 0.15). Overall and clinical success at EOT were significantly higher for possible IMD compared with proven/probable IMD (48.2% vs 36.2%; P = 0.01, 75.0% vs 63.1%; P = 0.01 respectively). Fewer drug-related TEAEs were reported with isavuconazole compared with voriconazole in patients with either proven/probable or possible IMD. Compared with patients with proven/probable IMD, those with possible IMD demonstrated higher overall and clinical success rates, supporting early initiation of antifungal treatment.

A rapid ultra-performance LC-MS/MS assay for determination of serum unbound fraction of voriconazole in cancer patients

BACKGROUND

Voriconazole (VOR), an antifungal agent, is clinically monitored to guide therapeutic dosing and avoid toxicity. It is believed that measurement of serum unbound VOR provides more accurate information, especially in hypoalbuminemia patients. We developed and validated an accurate, simple and fast test with ultrafiltration and ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) to measure unbound VOR in human serum.

METHODS

The Agilent UPLC system coupled with a SCIEX QTRAP4000 MS with a positive ionization mode was developed and validated for VOR analysis.

RESULTS

A good linearity was demonstrated from 0.02 to 2.5 μg/ml for unbound VOR (r² = 0.9969). The within-run and between-run accuracy and precision was <5% and < 6%. The levels of total VOR were well correlated with reference laboratory results. Serum unbound VOR levels were correlated with the total VOR levels (r = 0.78, p < 0.0001). There was a reverse correlation between unbound VOR fractions and plasma albumin levels (p < 0.05). In hypoalbuminemia patients, the unbound VOR levels were increased to a higher degree than total VOR.

CONCLUSION

This assay is suitable for monitoring both unbound and bound VOR in cancer patients especially in those with hypoalbuminemia in clinical laboratories. Measurement of unbound VOR offers a better approach in prediction of VOR toxicity.

Population pharmacokinetics of voriconazole and CYP2C19 polymorphisms for optimizing dosing regimens in renal transplant recipients

AIMS

The aims of the present study were to characterize the pharmacokinetics of voriconazole in renal transplant recipients and to identify factors significantly affecting pharmacokinetic parameters. We also aimed to explore the optimal dosing regimens for patients who developed invasive fungal infections.

METHODS

A total of 105 patients (342 concentrations) were included prospectively in a population pharmacokinetic analysis. Nonlinear mixed-effects models were developed using Phoenix NLME software. Dosing simulations were performed based on the final model.

RESULTS

A one-compartment model with first-order absorption and elimination was used to characterize voriconazole pharmacokinetics. Population estimates of clearance, volume of distribution and oral bioavailability were 2.88 l·h-1 , 169.3 l and 58%, respectively. The allele frequencies of cytochrome P450 gene (CYP) 2C19*2, *3 and *17 variants were 29.2%, 5.2% and 0.5%, respectively. CYP2C19 genotype had a significant effect on the clearance. Voriconazole trough concentrations in poor metabolizers were significantly higher than in intermediate metabolizers and extensive metabolizers alike. The volume of distribution increased with increased body weight. The oral bioavailability was substantially lower within 1 month after transplantation but increased with postoperative time. Dosing simulations indicated that during the early postoperative period, poor metabolizers could be treated with 150 mg intravenously or 250 mg orally twice daily; intermediate metabolizers with 200 mg intravenously or 350 mg orally twice daily; and extensive metabolizers with 300 mg intravenously twice daily.

CONCLUSIONS

Using a combination of CYP2C19 genotype and postoperative time to determine the initial voriconazole dosing regimens followed by therapeutic drug monitoring could help to advance individualized treatment in renal transplantation patients with invasive fungal infections.

Moderate correlation between systemic IL-6 responses and CRP with trough concentrations of voriconazole

Aims

Voriconazole (VCZ) exhibits wide intrapatient pharmacokinetic variability, which is disadvantageous because of its narrow therapeutic range. A considerable part of this variation remains unexplainable, despite extensive knowledge of this drug. It is hypothesized that inflammation has an impact on VCZ pharmacokinetics. In the present study, we investigated the correlation between VCZ trough concentrations and various cytokines.

Methods

A prospective single‐centre analysis was performed in adult haematology patients receiving VCZ for possible, probable or proven invasive fungal disease. A linear mixed model was built to explore the contribution of each of the seven pro‐ and anti‐inflammatory cytokines to VCZ trough levels. The Akaike information criterion (AIC) was used to determine the model that fitted the best.

Results

Twenty‐two patients, with a total of 143 combined samples of VCZ trough levels and cytokines, were included. A significant correlation (P < 0.005) was found between VCZ trough concentrations and interleukin (IL) 6, IL‐8 and C‐reactive protein (CRP). IL‐6 showed the lowest AIC, although differences with the other mediators were marginal.

Conclusion

VCZ trough concentrations correlate with IL‐6, IL‐8 and CRP levels but only moderately explain the variability in VCZ pharmacokinetics. Future prospective studies should be undertaken to confirm these findings, and incorporate the data obtained into pharmacokinetic models, to refine the predictive behaviour.

Impact of CYP2C19 Genotype and Liver Function on Voriconazole Pharmacokinetics in Renal Transplant Recipients

BACKGROUND

Invasive fungal infection (IFI) is one of the leading causes of early death after renal transplantation. Voriconazole (VRC) is the first-line drug of IFI. Because of the large inter- and intraindividual variability in VRC plasma concentrations and the narrow therapeutic window for treating patients with IFIs, it is crucial to study the factors which could influence pharmacokinetic variability. We performed a population pharmacokinetics (PPK) study of VRC for personalized medicine.

METHODS

A total of 125 trough concentrations (Cmin) from 56 patients were evaluated, retrospectively. Nonlinear mixed effect model was used to describe a PPK model that was internally validated by bootstrap method. Potential covariates included demographic characteristics, physiological and pathological data, concomitant medications, and CYP2C19 genotype.

RESULTS

A 1-compartment model with first-order absorption and elimination was fit to characterize the VRC pharmacokinetics in renal transplant recipients (RTRs). Aspartate aminotransferase (AST) had a significant influence on clearance (CL) while CYP2C19 genotype had a major impact on the volume of distribution (V). The parameters of CL and V were 4.76 L/h and 22.47 L, respectively. The final model was V (L) = 22.47 × [1 + 2.21 × (EM = 1)] × [1 + 4.67 × (IM = 1)] × [1 + 3.30 × (PM = 1)] × exp (0.96); CL (L/h) = 4.76 × (AST/33)^(-0.23) × exp (0.14). VRC Cmin in intermediate metabolizers was significantly higher than in extensive metabolizers.

CONCLUSIONS

Liver function and CYP2C19 polymorphism are major determinants of VRC pharmacokinetic variability in RTRs. Genotypes and clinical biomarkers can determine the initial scheme. Subsequently, therapeutic drug monitoring can optimize clinical efficacy and minimize toxicity. Hence, this is a feasible way to facilitate personalized medicine in RTRs. In addition, it is the first report about PPK of VRC in RTRs.

Issues in the management of invasive pulmonary aspergillosis in non-neutropenic patients in the intensive care unit: A role for isavuconazole

Background

Almost half of all cases of invasive aspergillosis (IA) occur in the intensive care unit (ICU), with mortality rates of 70–80% for probable or proven cases. IA has become a major concern among non-neutropenic patients in the ICU with chronic obstructive pulmonary disease (COPD) but although prompt, appropriate antifungal therapy is crucial, diagnosis in this situation is challenging. Criteria for a probable diagnosis in critically ill patients have been proposed to help to expedite therapy.

Methods

A case of probable invasive pulmonary aspergillosis (IPA) in a non-neutropenic patient admitted to the ICU was used to illustrate potential issues in the diagnostic work-up and management of patients in this setting.

Results

A non-neutropenic 69-year-old man with COPD receiving clomipramine was diagnosed in the ICU with probable invasive aspergillosis based on the presence of severe chronic obstructive pulmonary disease, suspected X-linked granulomatous disease, nodular infiltrates and galactogamman positivity on bronchoalveolar lavage (BAL) fluid. Voriconazole was unsuitable due to the patient's prolonged QT interval and risk of a drug–drug interaction with clomipramine. Isavuconazole was initiated and the patient's condition improved. The three-month course of isavuconazole treatment was well-tolerated and resulted in compete recovery of the patient.

Conclusions

Voriconazole is a standard first-line treatment for IA but intravenous therapy is associated with toxicity and the potential for drug–drug interactions. Isavuconazole is another first-line therapy which was effective and safe in the management of this critically ill non-neutropenic patient with baseline QT prolongation and potential drug–drug interactions with voriconazole.

Pharmacodynamics of Isavuconazole for Invasive Mold Disease: Role of Galactomannan for Real-Time Monitoring of Therapeutic Response

Background.

The ability to make early therapeutic decisions when treating invasive aspergillosis using changes in biomarkers as a surrogate for therapeutic response could significantly improve patient outcome.

Methods.

Cox proportional hazards model and logistic regression were used to correlate early changes in galactomannan index (GMI) to mortality and overall response, respectively, from patients with positive baseline GMI (≥0.5) and serial GMI during treatment from a phase 3 clinical trial for the treatment of invasive mold disease. Pharmacokinetic/pharmacodynamic (PK/PD) analysis in patients with isavuconazole plasma concentrations was conducted to establish the exposure necessary for GMI negativity at the end of therapy.

Results.

The study included 158 patients overall and 78 isavuconazole patients in the PK/PD modeling. By day 7, GMI increases of >0.25 units from baseline (3/130 survivors; 9/28 who died) significantly increased the risk of death compared to those with no increase or increases <0.25 (hazard ratio, 9.766; 95% confidence interval [CI], 4.356–21.9; P < .0001). For each unit decrease by day 7 from baseline, the odds of successful therapy doubled (odds ratio, 2.154; 95% CI, 1.173–3.955). An area under the concentration-versus-time curve over half-maximal effective concentration (AUC:EC₅₀) of 108.6 is estimated to result in a negative GMI at the end of isavuconazole therapy.

Conclusions.

Early trends in GMI are highly predictive of patient outcome. GMI increases by day 7 could be considered in context of clinical signs to trigger changes in treatment, once validated. Our data suggest that this improves survival by 10-fold and positive outcome by 3-fold. These data have important implications for individualized therapy for patients and clinical trials.

Clinical Trials Registration.

NCT00412893.

Improving survival of acute-on-chronic liver failure patients complicated with invasive pulmonary aspergillosis

The mortality of acute-on-chronic liver failure (ACLF) patients complicated with invasive pulmonary aspergillosis (IPA) was extremely high. We aimed to explore prognostic value of the Chronic Liver Failure-Sequential Organ Failure Assessment (CLIF-SOFA) lung score and to establish an optimal voriconazole regimen for ACLF patients complicated with IPA. We retrospectively screened hospitalized ACLF patients in our hospital from July 2011 to April 2016, from which 20 probable IPA cases were diagnosed. Along with onsets of IPA, deteriorated diseases severity, especially lung conditions were found in those 20 ACLF patients. It was found that IPA patients with CLIF-SOFA lung score <2 had better 28-day survival than those with lung score >1 (11/13 vs 0/7, p < 0.001). Based on plasma voriconazole concentration measurement, an optimal voriconazole regimen (loading doses: 0.2 g twice daily; maintenance doses, 0.1 g once daily) was established, which resulted in rational trough plasma drug concentrations (1-5 μg/mL), good clinical outcomes (90-day survival rate of 6/8) and no observed adverse events. In conclusion, CLIF-SOFA lung score >1 was able to identify ACLF patients complicated with IPA encountering much higher 28-day mortality. An optimal voriconazole regimen was safe and effective in our ACLF patients complicated with IPA.

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.

Pharmacodynamic studies of voriconazole: informing the clinical management of invasive fungal infections

INTRODUCTION

Voriconazole is a broad-spectrum antifungal agent commonly used to treat invasive fungal infections (IFI), including aspergillosis, candidiasis, Scedosporium infection, and Fusarium infection. IFI often occur in immunocompromised patients, leading to increased morbidity and mortality.

AREAS COVERED

The objective of this review is to summarize the pharmacodynamic properties of voriconazole and to provide considerations for potential optimal dosing strategies. Studies have demonstrated superior clinical response when an AUC/MIC >25 or Cmin/MIC >1 is attained in adult patients, correlating to a trough concentration range as narrow as 2-4.5 mg/L; however, these targets are poorly established in the pediatric population. Topics in this discussion include voriconazole use in multiple age groups, predisposing patient factors for IFI, and considerations for clinicians managing IFI. Expert commentary: The relationship between voriconazole dosing and exposure is not well defined due to the large inter- and intra-subject variability. Development of comprehensive decision support tools for individualizing dosing, particularly in children who require higher dosing, will help to increase the probability of achieving therapeutic efficacy and decrease sub-therapeutic dosing and adverse events.

Influence of CYP2C19 Genotypes on the Occurrence of Adverse Drug Reactions of Voriconazole among Hematological Patients after Allo-HSCT

The aim of this study was to determine the influence of different CYP2C19 genotypes on selected liver function parameters, and ADR occurrence during VCZ prophylaxis in adult patients after allo-HSCT (allogeneic hematopoietic stem cell transplantation). CYP2C19 mutations were determined in a cohort of 30 adults using PCR-RFLP methods established by Sim et al. and Goldstein and Blaisdell. The patients’ protocol included biometrical and biochemical data, information on the underlying disease, chemotherapy, molds infections occurring during VCZ treatment, adverse drug reactions typical for the use of voriconazole, and probable drug - drug interactions. The observation and reporting of ADR took place from the −1 until the +20th day of VCZ therapy. For statistical analysis the χ2 test was used (p < 0.05). Among the examined patients 23 suffered from at least one side effect during VCZ therapy. Most frequent ADR were gastrointestinal disturbances (n = 15), nervous system (n = 11) and skin (n = 7) disorders. Patients with at least one loss of function allele (*2) were more likely to experience adverse drug reactions than those, with different genotypes. Due to the limited number of patients the result could not be proven with a statistical significance. Previous determination of CYP2C19 genotype may be a useful tool for prevention of adverse drug reactions during VCZ prophylaxis among patients after allo-HSCT.

Prognostic value of galactomannan: current evidence for monitoring response to antifungal therapy in patients with invasive aspergillosis

Galactomannan (GM) is a polysaccharide present in the cell wall of Aspergillus spp. that is released during growth of the organism. It has been successfully used to aide in the diagnosis of invasive aspergillosis allowing for earlier recognition of disease compared to conventional methods. Since its implementation in the clinic as a diagnostic tool, GM has been used in experimental models to measure therapeutic response. Several clinical studies describe the prognostic value of GM. Herein, we review the evidence supporting the utilization of GM antigen as a biomarker to measure response to systemic antifungal therapy.

Elevated Voriconazole Level Associated With Hallucinations and Suicidal Ideation: A Case Report

Voriconazole, a broad-spectrum antifungal, has been associated with visual and auditory hallucinations. We report the case of patient being treated with voriconazole for pulmonary aspergillosis who developed visual hallucinations and new suicidal ideation with plan. Voriconazole troughs were supratherapeutic (9.0 mcg/mL) and the patient was positive for the CYP2C19*1/*2 allele.

Comparative Evaluation of the Predictive Performances of Three Different Structural Population Pharmacokinetic Models To Predict Future Voriconazole Concentrations

Bayesian methods for voriconazole therapeutic drug monitoring (TDM) have been reported previously, but there are only sparse reports comparing the accuracy and precision of predictions of published models. Furthermore, the comparative accuracy of linear, mixed linear and nonlinear, or entirely nonlinear models may be of high clinical relevance. In this study, models were coded into individually designed optimum dosing strategies (ID-ODS) with voriconazole concentration data analyzed using inverse Bayesian modeling. The data used were from two independent data sets, patients with proven or suspected invasive fungal infections (n = 57) and hematopoietic stem cell transplant recipients (n = 10). Observed voriconazole concentrations were predicted whereby for each concentration value, the data available to that point were used to predict that value. The mean prediction error (ME) and mean squared prediction error (MSE) and their 95% confidence intervals (95% CI) were calculated to measure absolute bias and precision, while ΔME and ΔMSE and their 95% CI were used to measure relative bias and precision, respectively. A total of 519 voriconazole concentrations were analyzed using three models. MEs (95% CI) were 0.09 (-0.02, 0.22), 0.23 (0.04, 0.42), and 0.35 (0.16 to 0.54) while the MSEs (95% CI) were 2.1 (1.03, 3.17), 4.98 (0.90, 9.06), and 4.97 (-0.54 to 10.48) for the linear, mixed, and nonlinear models, respectively. In conclusion, while simulations with the linear model were found to be slightly more accurate and similarly precise, the small difference in accuracy is likely negligible from the clinical point of view, making all three approaches appropriate for use in a voriconazole TDM program.

Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the Infectious Diseases Society of America

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA), a progressive fungal allergic lung disease, is a common complication of asthma or cystic fibrosis. Although ABPA has been recognized since the 1950s, recent research has underscored the importance of Th2 immune deviation and granulocyte activation in its pathogenesis. There is also strong evidence of widespread under-diagnosis due to the complexity and lack of standardization of diagnostic criteria. Treatment has long focused on downregulation of the inflammatory response with prolonged courses of oral glucocorticosteroids, but more recently concerns with steroid toxicity and availability of new treatment modalities has led to trials of oral azoles, inhaled amphotericin, pulse intravenous steroids, and subcutaneously-injected anti-IgE monoclonal antibody omalizumab, all of which show evidence of efficacy and reduced toxicity.

Trough concentration of voriconazole and its relationship with efficacy and safety: a systematic review and meta-analysis

This meta-analysis showed trough concentrations of 0.5 mg/L to be the lower limit of voriconazole during treatment, whereas trough concentrations of 3.0 mg/L were associated with an increased risk of moderate to severe hepatotoxicity, particularly for the Asian population.

Objectives

The optimum trough concentration of voriconazole for clinical response and safety is controversial. The objective of this review was to determine the optimum trough concentration of voriconazole and evaluate its relationship with efficacy and safety.

Methods

MEDLINE, EMBASE, ClinicalTrials.gov, the Cochrane Library and three Chinese literature databases were searched. Observational studies that compared clinical outcomes below and above the trough concentration cut-off value were included. We set the trough concentration cut-off value for efficacy as 0.5, 1.0, 1.5, 2.0 and 3.0 mg/L and for safety as 3.0, 4.0, 5.0, 5.5 and 6.0 mg/L. The efficacy outcomes were invasive fungal infection-related mortality, all-cause mortality, rate of successful treatment and rate of prophylaxis failure. The safety outcomes included incidents of hepatotoxicity, neurotoxicity and visual disorders.

Results

A total of 21 studies involving 1158 patients were included. Compared with voriconazole trough concentrations of >0.5 mg/L, levels of <0.5 mg/L significantly decreased the rate of treatment success (risk ratio = 0.46, 95% CI 0.29–0.74). The incidence of hepatotoxicity was significantly increased with trough concentrations >3.0, >4.0, >5.5 and >6.0 mg/L. The incidence of neurotoxicity was significantly increased with trough concentrations >4.0 and >5.5 mg/L.

Conclusions

A voriconazole level of 0.5 mg/L should be considered the lower threshold associated with efficacy. A trough concentration >3.0 mg/L is associated with increased hepatotoxicity, particularly for the Asian population, and >4.0 mg/L is associated with increased neurotoxicity.

Autoinduction of voriconazole metabolism in a child with invasive pulmonary aspergillosis

Inter- and intra-patient variability in voriconazole pharmacokinetics has been described in children as the result of age-specific differences in hepatic metabolism, saturable nonlinear pharmacokinetics, CYP450 2C19 polymorphisms, decreased bioavailability compared with adults, and drug-drug interactions. We introduce dose-dependent autoinduction of metabolism as another cause for altered voriconazole pharmacokinetics in children and summarize previously published literature on this phenomenon. A 10-year-old girl with severe aplastic anemia developed invasive pulmonary aspergillosis after high-dose cyclophosphamide therapy and required high doses of voriconazole for longer than 2 months. She initially achieved a therapeutic trough of 1.4 μg/ml on voriconazole 11 mg/kg/dose orally every 12 hours but required dose escalations to 9.3 mg/kg/dose orally every 8 hours to maintain a trough above 1 μg/ml. Because there were no changes in concomitant medications, route of administration, adherence, or oral intake, we conclude that the only plausible explanation for the precipitous drop in voriconazole troughs was autoinduction of metabolism, a phenomenon previously reported in adults receiving higher than usual doses or prolonged courses (longer than 2 months). These data highlight the need for continued therapeutic drug monitoring of voriconazole after initial therapeutic troughs are achieved because autoinduction of metabolism can lead to significant declines in subsequent voriconazole troughs, potentially leading to treatment failure.

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.

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.