Therapeutic drug monitoring (TDM) of antifungal agents: guidelines from the British Society for Medical Mycology

Pharmacokinetics and safety of posaconazole delayed-release tablets for invasive fungal infections

Posaconazole is a broad-spectrum triazole antifungal agent with potent activity against various pathogenic fungi, including yeast and moulds. Clinical studies have demonstrated that this agent is efficacious as prophylaxis against invasive fungal infections in patients at high risk, and may also be useful as salvage therapy against invasive aspergillosis and mucormycosis. However, the bioavailability of posaconazole following administration by oral suspension, which was the only formulation clinically available for many years, is highly variable and negatively influenced by several factors. Because of this, many patients had subtherapeutic or undetectable posaconazole levels when the oral suspension was used. To overcome this limitation, a delayed-release tablet was developed and is now available for clinical use. Hot-melt extrusion technology is used to combine a pH-sensitive polymer with posaconazole to produce a formulation that releases the drug in the elevated pH of the intestine where absorption occurs rather than in the low-pH environment of the stomach. This results in enhanced bioavailability and increased posaconazole exposure. Studies in healthy volunteers have demonstrated significantly higher and more consistent exposures with the tablet formulation compared to the oral suspension. In addition, pharmacokinetic parameters following administration of the tablets were not significantly affected by medications that raise gastric pH or increase gastric motility, and the tablets could also be administered without regard to food. Similar results have also been found in patients at high risk for invasive fungal infections who have received posaconazole tablets. The tablet formulation also appears to be well tolerated to date, although data regarding clinical efficacy are needed.

Voriconazole therapeutic drug monitoring: results of a prematurely discontinued randomized multicenter trial

BACKGROUND

Voriconazole (VOR) levels are highly variable, with potential implications to both efficacy and safety. We hypothesized that VOR therapeutic drug monitoring (TDM) will decrease the incidence of treatment failures and adverse events (AEs).

METHODS

We initiated a prospective, randomized, non-blinded multicenter study to compare clinical outcomes in adult patients randomized to standard dosing (clinician-driven) vs. TDM (doses adjusted based on levels). VOR trough levels were obtained on day 5, 14, 28, and 42 (or at completion of drug; ± 3 days). Real-time dose adjustments were made to maintain a range between 1-5 μg/mL on the TDM-arm, while levels were assessed retrospectively in the standard-arm. Patient questionnaires were administered to assess subjective AEs.

RESULTS

The study was discontinued prematurely, after 29 patients were enrolled. Seventeen (58.6%) patients experienced 38 AEs: visual changes (22/38, 57.9%), neurological symptoms (13/38, 34.2%), and liver abnormalities (3/38, 7.9%). VOR was discontinued in 7 (25%) patients because of an AE (4 standard-arm, 3 TDM-arm). VOR levels were frequently out of range in the standard-arm (8 tests >5 μg/mL; 9 tests <1 μg/mL). Three dose changes occurred in the TDM-arm for VOR levels <1 μg/mL. Levels decreased over time in the standard-arm, with mean VOR levels lower at end of therapy compared to TDM (1.3 vs. 4.6 μg/mL, P = 0.008).

CONCLUSIONS

VOR TDM has become widespread clinical practice, based on known variability in drug levels, which impaired accrual in this study. Although comparative conclusions are limited, observations of variability and waning levels over time support TDM.

Therapeutic drug monitoring of antimicrobials

As pathology services become more centralized and automated, the measurement of therapeutic antimicrobial drugs concentrations is increasingly performed in clinical biochemistry or 'blood science' laboratories. This review outlines key groups of antimicrobial agents: aminoglycosides, glycopeptides, antifungal agents and antituberculosis agents, their role in managing infectious diseases, and the reasons why serum concentration measurement is important.

A pharmacokinetic analysis of posaconazole oral suspension in the serum and alveolar compartment of lung transplant recipients

Invasive fungal infections cause significant morbidity and mortality after lung transplantation. Fungal prophylaxis following lung transplantation is not standardised, with transplant centres utilising a variety of regimens. Posaconazole is a broad-spectrum antifungal triazole that requires further investigation within the setting of lung transplantation. This prospective, single-centre, observational study explored the pharmacokinetics of posaconazole oral suspension (POS) in the early perioperative period following lung transplantation in 26 patients. Organ recipients were scheduled to receive 400mg POS twice daily for 6 weeks as primary antifungal prophylaxis. Therapeutic drug monitoring (TDM) of serum posaconazole levels was performed in accordance with local clinical protocols. Bronchoalveolar lavage fluid (BALF) was sampled during routine bronchoscopies. Posaconazole levels were measured both in serum and BALF using mass spectrometry. Posaconazole levels were highly variable within lung transplant recipients during the perioperative period and did not achieve 'steady-state'. Serum posaconazole concentrations positively correlated with levels within the BALF (r=0.5527; P=0.0105). Of the 26 patients, 10 failed to complete the study for multiple reasons and so the trial was terminated early. Unlike study findings in stable recipients, serum posaconazole levels rarely achieved steady-state in the perioperative period; however, they do reflect the concentrations within the airways of newly transplanted lungs. The role of POS as primary prophylaxis in the perioperative period is uncertain, but if used TDM may be helpful for determining attainment of therapeutic levels.

Bioassay for Determining Voriconazole Serum Levels in Patients Receiving Combination Therapy with Echinocandins

Voriconazole levels were determined with high-performance liquid chromatography (HPLC) and a microbiological agar diffusion assay using a Candida parapsilosis isolate in 103 serum samples from an HPLC-tested external quality control program (n = 39), 21 patients receiving voriconazole monotherapy (n = 39), and 7 patients receiving combination therapy (n = 25). The results of the bioassay were correlated with the results obtained from the external quality control program samples and with the HPLC results in sera from patients on voriconazole monotherapy and on combination therapy with an echinocandin (Spearman's rank correlation coefficient [rs], > 0.93; mean ± standard error of the mean [SEM] % difference, <12% ± 3.8%).

Introduction to the updated Australian and New Zealand consensus guidelines for the use of antifungal agents in the haematology/oncology setting, 2014

This article introduces the second revision of the Australian and New Zealand consensus guidelines for the use of antifungal agents in the haematology/oncology setting. The current update occurs within the context of a growing population at risk of invasive fungal disease, improved understanding of risk factors, availability of new diagnostic tests, a much-expanded evidence base and changing clinical paradigms. Here, we provide an overview of the history and purpose of the guidelines, including changes in scope since the last clinical update was published in 2008. The process for development, and for enabling review of draft recommendations by end-users and other relevant stakeholders, is described. The approach to assigning levels of evidence and grades of recommendation is also provided, along with a comparison to international grading systems.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy, 2014

Antifungal agents may be associated with significant toxicity or drug interactions leading to sub-therapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy. These risks may be minimised by clinical assessment, laboratory monitoring, avoidance of particular drug combinations and dose modification. Specific measures, such as the optimal timing of oral drug administration in relation to meals, use of pre-hydration and electrolyte supplementation may also be required. Therapeutic drug monitoring (TDM) of antifungal agents is warranted, especially where non-compliance, non-linear pharmacokinetics, inadequate absorption, a narrow therapeutic window, suspected drug interaction or unexpected toxicity are encountered. Recommended indications for voriconazole and posaconazole TDM in the clinical management of haematology patients are provided. With emerging knowledge regarding the impact of pharmacogenomics upon metabolism of azole agents (particularly voriconazole), potential applications of pharmacogenomic evaluation to clinical practice are proposed.

Consensus guidelines for the treatment of invasive mould infections in haematological malignancy and haemopoietic stem cell transplantation, 2014

Mould species represent the pathogens most commonly associated with invasive fungal disease in patients with haematological malignancies and patients of haemopoietic stem cell transplants. Invasive mould infections in these patient populations, particularly in the setting of neutropenia, are associated with high morbidity and mortality, and significantly increase the complexity of management. While Aspergillus species remain the most prevalent cause of invasive mould infections, Scedosporium and Fusarium species and the Mucormycetes continue to place a significant burden on the immunocompromised host. Evidence also suggests that infections caused by rare and emerging pathogens are increasing within the setting of broad-spectrum antifungal prophylaxis and improved survival times placing immunosuppressed patients at risk for longer. These guidelines present evidence-based recommendations for the antifungal management of common, rare and emerging mould infections in both adult and paediatric populations. Where relevant, the role of surgery, adjunctive therapy and immunotherapy is also discussed.

Structure-Functional Characterization of Cytochrome P450 Sterol 14α-Demethylase (CYP51B) from Aspergillus fumigatus and Molecular Basis for the Development of Antifungal Drugs

Aspergillus fumigatus is the opportunistic fungal pathogen that predominantly affects the immunocompromised population and causes 600,000 deaths/year. The cytochrome P450 51 (CYP51) inhibitor voriconazole is currently the drug of choice, yet the treatment efficiency remains low, calling for rational development of more efficient agents. A. fumigatus has two CYP51 genes, CYP51A and CYP51B, which share 59% amino acid sequence identity. CYP51B is expressed constitutively, whereas gene CYP51A is reported to be inducible. We expressed, purified, and characterized A. fumigatus CYP51B, including determination of its substrate preferences, catalytic parameters, inhibition, and x-ray structure in complexes with voriconazole and the experimental inhibitor (R)-N-(1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide (VNI). The enzyme demethylated its natural substrate eburicol and the plant CYP51 substrate obtusifoliol at steady-state rates of 17 and 16 min(-1), respectively, but did not metabolize lanosterol, and the topical antifungal drug miconazole was the strongest inhibitor that we identified. The x-ray crystal structures displayed high overall similarity of A. fumigatus CYP51B to CYP51 orthologs from other biological kingdoms but revealed phylum-specific differences relevant to enzyme catalysis and inhibition. The complex with voriconazole provides an explanation for the potency of this relatively small molecule, whereas the complex with VNI outlines a direction for further enhancement of the efficiency of this new inhibitory scaffold to treat humans afflicted with filamentous fungal infections.

Randomised, multicentre trial of micafungin vs. an institutional standard regimen for salvage treatment of invasive aspergillosis

Invasive aspergillosis remains associated with significant morbidity and mortality, necessitating new options for salvage therapy. The objective of this study was to evaluate the efficacy and safety of micafungin as salvage monotherapy in patients with invasive aspergillosis. Patients with proven or probable invasive aspergillosis, who were refractory or intolerant to previous systemic antifungal therapy, were randomised 2 : 1 to receive 300 mg day(-1) intravenous micafungin monotherapy or an intravenous control monotherapy [lipid amphotericin B (5 mg kg(-1) day(-1)), voriconazole (8 mg kg(-1) day(-1)) or caspofungin (50 mg day(-1))] for 3-12 weeks. Patients underwent final assessment 12 weeks after treatment start. Seventeen patients with invasive aspergillosis (proven, n = 2; probable, n = 14; not recorded, n = 1) participated in the study (micafungin arm, n = 12; control arm, n = 5). Three patients each in the micafungin (25.0%; 95% CI: 5.5-57.2) and control arm (60.0%; 95% CI: 14.7-94.7) had successful therapy at end of treatment as assessed by an Independent Data Review Board. Eleven patients died; six due to invasive aspergillosis. No deaths were considered related to study treatment. During this study it became increasingly common to use combination treatment for salvage therapy. Consequently, enrolment was low and the study was discontinued early. No clear trends in efficacy and safety can be concluded.

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.

Synergistic effects of tea catechin epigallocatechin gallate and antimycotics against oral Candida species

OBJECTIVE

Epigallocatechin gallate (EGCG), the major antimicrobial tea polyphenol, has been reported to inhibit the growth of Candida albicans planktonic cells and enhance the antifungal activity of antimycotics. We hypothesised that synergism exists between EGCG and conventional antimycotics against biofilms of Candida species.

DESIGN

The minimal inhibitory concentrations (MIC) of EGCG, miconazole, fluconazole and amphotericin B against planktonic cells and the sessile MIC (SMIC) against biofilms of Candida albicans, Candida parapsilosis, Candida tropicalis, Candida glabrata, Candida kefyr and Candida krusei were determined by a microdilution method. For assessment of biofilm metabolic activity, the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay was used. The interactions between EGCG and antimycotics were evaluated by checkerboard microdilution assay and determined by fractional inhibitory concentration index (FIC).

RESULTS

Synergism was observed between EGCG and miconazole, fluconazole or amphotericin B against most test planktonic and biofilm cells of Candida species (FIC≤0.5). All biofilm cells were significantly more resistant to EGCG and antimycotics (20-3200 times higher) compared with their planktonic counterparts.

CONCLUSIONS

We conclude that EGCG enhances the antifungal effects of miconazole, fluconazole and amphotericin B. Combined treatment with EGCG may lower the dosages of antimycotics, thus preventing adverse effects and the emergence of drug-resistant oral Candida species.

Structural Insights into Binding of the Antifungal Drug Fluconazole to Saccharomyces cerevisiae Lanosterol 14α-Demethylase

Infections by fungal pathogens such as Candida albicans and Aspergillus fumigatus and their resistance to triazole drugs are major concerns. Fungal lanosterol 14α-demethylase belongs to the CYP51 class in the cytochrome P450 superfamily of enzymes. This monospanning bitopic membrane protein is involved in ergosterol biosynthesis and is the primary target of azole antifungal drugs, including fluconazole. The lack of high-resolution structural information for this drug target from fungal pathogens has been a limiting factor for the design of modified triazole drugs that will overcome resistance. Here we report the X-ray structure of full-length Saccharomyces cerevisiae lanosterol 14α-demethylase in complex with fluconazole at a resolution of 2.05 Å. This structure shows the key interactions involved in fluconazole binding and provides insight into resistance mechanisms by revealing a water-mediated hydrogen bonding network between the drug and tyrosine 140, a residue frequently found mutated to histidine or phenylalanine in resistant clinical isolates.

Superior Serum Concentrations with Posaconazole Delayed-Release Tablets Compared to Suspension Formulation in Hematological Malignancies

Posaconazole (PCZ), approved for prophylaxis against invasive fungal disease in high-risk patients, is commercially available orally as a suspension formulation (PCZ-susp) and as a delayed-release tablet (PCZ-tab). We evaluated the serum steady-state concentrations (Css) of PCZ stratified by the administered formulation for antifungal prophylaxis in patients with myeloid malignancies (n = 150). The primary outcome was the attainment rate of the target Css of ≥700 ng/ml. Secondary outcomes included toxicity assessment (hepatotoxicity and corrected QT [QTc] interval prolongation) and breakthrough fungal infections. Patients who received the PCZ-susp (n = 118) or PCZ-tab (n = 32) and had PCZ Css assessment after at least 7 days of therapy were eligible. The median Css in the PCZ-susp group was 390 ng/ml (range, 51 to 1,870 ng/ml; mean, 436 ng/ml) compared to 1,740 ng/ml (range, 662 to 3,350 ng/ml; mean, 1,781 ng/ml) in the PCZ-tab group (P < 0.0001). The percentages of patients achieving the target goal of ≥700 ng/ml were 17% versus 97%, respectively (P < 0.0001). Hepatotoxicity (grade 2 or higher) occurred in 1 patient in each group. QTc interval measurements were available for 32 patients in the PCZ-susp group and for 12 patients in the PCZ-tab group, and prolonged intervals of grade 2 or higher were noted in 9% (n = 3) and 17% (n = 2), respectively (P = 0.6). Breakthrough fungal infections in the PCZ-susp and PCZ-tab groups were 7% (n = 8) and 3% (n = 1), respectively (P = 0.68). We conclude that the use of PCZ-tab was associated with higher Css and with the probability of achieving therapeutic goals without worsening of adverse effects.

Azole-resistant aspergillosis

Azole-resistance in Aspergillus fumigatus is emerging and is becoming an increasing problem in the management of aspergillosis. Two types of development of resistance have been described; resistance acquired during azole treatment in an individual patient and through environmental exposure to fungicides. The main molecular mechanism of azole resistance in A. fumigatus is explained by mutations in the cyp51A-gene. The environmental route of resistance development is particularly worrying and may affect all patients whether azole exposed or naïve, and whether suffering from acute or chronic aspergillosis. No management guidelines to assist clinicians confronted with azole-resistant aspergillosis are available and pre-clinical and clinical evidence supporting treatment choices is scarce.

British Society for Medical Mycology best practice recommendations for the diagnosis of serious fungal diseases

Invasive fungal diseases are an important cause of morbidity and mortality in a wide range of patients, and early diagnosis and management are a challenge. We therefore did a review of the scientific literature to generate a series of key recommendations for the appropriate use of microbiological, histological, and radiological diagnostic methods for diagnosis of invasive fungal diseases. The recommendations emphasise the role of microscopy in rapid diagnosis and identification of clinically significant isolates to species level, and the need for susceptibility testing of all Aspergillus spp, if treatment is to be given. In this Review, we provide information to improve understanding of the importance of antigen detection for cryptococcal disease and invasive aspergillosis, the use of molecular (PCR) diagnostics for aspergillosis, and the crucial role of antibody detection for chronic and allergic aspergillosis. Furthermore, we consider the importance of histopathology reporting with a panel of special stains, and emphasise the need for urgent (<48 hours) and optimised imaging for patients with suspected invasive fungal infection. All 43 recommendations are auditable and should be used to ensure best diagnostic practice and improved outcomes for patients.

Pharmacodynamics of amphotericin B deoxycholate, amphotericin B lipid complex, and liposomal amphotericin B against Aspergillus fumigatus

Amphotericin B is a first-line agent for the treatment of invasive aspergillosis. However, relatively little is known about the pharmacodynamics of amphotericin B for invasive pulmonary aspergillosis. We studied the pharmacokinetics (PK) and pharmacodynamics (PD) of amphotericin B deoxycholate (DAMB), amphotericin B lipid complex (ABLC), and liposomal amphotericin B (LAMB) by using a neutropenic-rabbit model of invasive pulmonary aspergillosis. The study endpoints were lung weight, infarct score, and levels of circulating galactomannan and (1 → 3)-β-D-glucan. Mathematical models were used to describe PK-PD relationships. The experimental findings were bridged to humans by Monte Carlo simulation. Each amphotericin B formulation induced a dose-dependent decline in study endpoints. Near-maximal antifungal activity was evident with DAMB at 1 mg/kg/day and ABLC and LAMB at 5 mg/kg/day. The bridging study suggested that the "average" patient receiving LAMB at 3 mg/kg/day was predicted to have complete suppression of galactomannan and (1 → 3)-β-D-glucan levels, but 20 to 30% of the patients still had a galactomannan index of >1 and (1 → 3)-β-D-glucan levels of >60 pg/ml. All formulations of amphotericin B induce a dose-dependent reduction in markers of lung injury and circulating fungus-related biomarkers. A clinical dosage of liposomal amphotericin B of 3 mg/kg/day is predicted to cause complete suppression of galactomannan and (1 → 3)-β-D-glucan levels in the majority of patients.

Variability of voriconazole plasma concentrations after allogeneic hematopoietic stem cell transplantation: impact of cytochrome p450 polymorphisms and comedications on initial and subsequent trough levels

Voriconazole (VRC) plasma trough concentrations (Cmin) are highly variable, and this could affect treatment efficacy and safety in patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT). We aimed to describe the intra- and interindividual variation of VRC Cmin throughout the course of VRC therapy and to identify the determinants of this variation. Clinical data, medications, and VRC Cmin (n = 308) of 33 AHSCT patients were retrospectively collected. Cytochrome P450 (CYP450) genotypes of CYP2C19, CYP3A4, and CYP3A5 patients were retrospectively determined before allografting, and a combined genetic score was calculated for each patient. The higher the genetic score, the faster the metabolism of the patient. The VRC Cmin inter- and intraindividual coefficients of variation were 84% and 68%, respectively. The VRC dose (D) was correlated to VRC Cmin (r = 0.412, P < 0.0001) only for oral administration. The administration route and the genetic score significantly affected the initial VRC Cmin. Considering oral therapy, patients with a genetic score of <2 had higher initial VRC Cmin/D than patients with a genetic score of >2 (P = 0.009). Subsequent VRC Cmin remained influenced by the genetic score (P = 0.004) but were also affected by pump proton inhibitor comedication (P < 0.0001). The high variability of VRC Cmin in AHSCT patients is partially explained by the route of administration, treatment with pump proton inhibitors, and the combined genetic score. This study suggests the interest in combined genetic score determination to individualize a priori the VRC dose and underlines the need for longitudinal therapeutic drug monitoring to adapt subsequent doses to maintain the VRC Cmin within the therapeutic range.

Anti-infective prophylaxis in pediatric patients with acute myeloid leukemia

Pediatric patients undergoing treatment for acute myeloid leukemia (AML) are at high risk for infectious complications, predominantly due to Gram-negative bacteria, viridans group streptococci and fungal pathogens. In order to prevent infections in these patients, most institutions have implemented a number of non-pharmacological approaches to supportive care. In addition, antibiotic prophylaxis reduces bacterial infection, but may increase the emergence of resistance. Antifungal prophylaxis is generally recommended for children with AML. Whereas the use of hematopoietic growth factors has not resulted in improved survival, the efficacy of prophylactic granulocyte transfusions has to be determined.

Switching from posaconazole suspension to tablets increases serum drug levels in leukemia patients without clinically relevant hepatotoxicity

We evaluated posaconazole serum concentrations and hepatotoxicity in 12 leukemia patients who transitioned from posaconazole suspension to tablets. Patients who switched to tablets had significantly increased posaconazole concentrations (median: suspension, 748 ng/ml; tablet, 1,910 ng/ml; P < 0.01) without clinically relevant hepatotoxicity.

Understanding variability in posaconazole exposure using an integrated population pharmacokinetic analysis

Posaconazole oral suspension is widely used for antifungal prophylaxis and treatment in immunocompromised patients, with highly variable pharmacokinetics reported in patients due to inconsistent oral absorption. This study aimed to characterize the pharmacokinetics of posaconazole in adults and investigate factors that influence posaconazole pharmacokinetics byusing a population pharmacokinetic approach. Nonlinear mixed-effects modeling was undertaken for two posaconazole studies in patients and healthy volunteers. The influences of demographic and clinical characteristics, such as mucositis, diarrhea, and drug-drug interactions, on posaconazole pharmacokinetics were investigated using a stepwise forward inclusion/backwards deletion procedure. A total of 905 posaconazole concentration measurements from 102 participants were analyzed. A one-compartment pharmacokinetic model with first-order oral absorption with lag time and first-order elimination best described posaconazole pharmacokinetics. Posaconazole relative bioavailability was 55% lower in patients who received posaconazole than in healthy volunteers. Coadministration of proton pump inhibitors (PPIs) or metoclopramide, as well as the occurrence of mucositis or diarrhea, reduced posaconazole relative bioavailability by 45%, 35%, 58%, and 45%, respectively, whereas concomitant ingestion of a nutritional supplement significantly increased bioavailability (129% relative increase). Coadministration of rifampin or phenytoin increased apparent posaconazole clearance by more than 600%, with a smaller increase observed with fosamprenavir (34%). Participant age, weight, or sex did not significantly affect posaconazole pharmacokinetics. Posaconazole absorption was reduced by a range of commonly coadministered medicines and clinical complications, such as mucositis and diarrhea. Avoidance of PPIs and metoclopramide and administration with food or a nutritional supplement are effective strategies to increase posaconazole absorption.

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.

Five year results of an international proficiency testing programme for measurement of antifungal drug concentrations

OBJECTIVES

Since 2007 the Dutch Association for Quality Assessment in Therapeutic Drug Monitoring (KKGT) has organized an international interlaboratory proficiency testing (PT) programme for measurement of antifungal drugs in plasma. We describe the 5 year results of the laboratories' performance.

METHODS

Twice a year, laboratories received a set of blind plasma samples containing low or high concentrations of fluconazole, itraconazole, hydroxyitraconazole, posaconazole, voriconazole and flucytosine. Participating laboratories were asked to report their results within 6 weeks after dispatch and provide details of their analytical methods. Results deviating >20% from the weighed-in concentration were considered inaccurate. Four-way ANOVA was performed to assess the effect of antifungal drug measured, concentration, analytical method and performing laboratory on the absolute inaccuracy. In 2012, a questionnaire based on the CLSI guidelines was dispatched with the request to provide input on sources of error.

RESULTS

Fifty-seven laboratories (13 countries) reported 2251 results (287 fluconazole, 451 itraconazole, 348 hydroxyitraconazole, 402 posaconazole, 652 voriconazole and 111 flucytosine) in 5 years. Analyses were performed using HPLC (55.0%), LC-MS(/MS) (43.4%), UPLC (1.4%) or GC-MS (0.2%). Overall, 432 (19.2%) analyses were inaccurate. The performing laboratory was the only factor clearly associated with inaccuracies. The questionnaire results indicated that laboratories encounter significant problems analysing low concentrations (15.4% of all inaccuracies).

CONCLUSIONS

Results of the PT programme suggest that one out of five measurements is inaccurate. The performing laboratory is the main determinant of inaccuracy, suggesting that internal quality assurance is pivotal in preventing inaccuracies, irrespective of the antifungal drug measured, concentration and analytical equipment.

Burden and distinctive character of allergic bronchopulmonary aspergillosis in India

Allergic bronchopulmonary aspergillosis (ABPA) is an insidious pulmonary disorder caused by hypersensitivity reactions mounted against Aspergillus fumigatus. Usually, complicating the course of patients with asthma and cystic fibrosis, the affliction has recently been described in chronic obstructive pulmonary disease and pulmonary tuberculosis-related fibrocavitary disease. Patients commonly present with poorly controlled asthma, recurrent pulmonary infiltrates and bronchiectasis. More than six decades have elapsed since the first description of this entity; however, the condition remains poorly understood. The International Society for Human and Animal Mycology has formed a working group to address the deficiencies associated with understanding of this disorder. New criteria have been laid down for diagnosis and staging of the disorder, so as to simplify the identification and management of this condition. This review summarizes the recent advances that have taken place in this condition with special emphasis on the burden and distinct character of ABPA in the Indian subcontinent.