Variability of Voriconazole Trough Levels in Haematological Patients: Influence of Comedications with cytochrome P450(CYP) Inhibitors and/or with CYP Inhibitors plus CYP Inducers

The Effect of Rifapentine and Rifampicin on Serum Voriconazole Levels Persist for 5 Days and 7 Days or More After Discontinuation in Tuberculosis Patients with Chronic Pulmonary Aspergillosis

Purpose

Voriconazole, a first-line therapeutic agent for chronic pulmonary aspergillosis, is metabolized by the cytochrome 450 enzymes, specifically CYP2C19 and CYP3A4. Rifampicin and rifapentine act as inducers of the cytochrome P450 enzyme. The current study explored the potential drug interactions arising from the co-administration of voriconazole with either rifampicin or rifapentine, as well as the duration of this effect on serum voriconazole levels after discontinuation of rifampicin or rifapentine.

Patients and Methods

A retrospective study was conducted in tuberculosis patients with chronic pulmonary aspergillosis. These patients underwent a combination therapy involving voriconazole and rifampicin or rifapentine, or they were treated with voriconazole after discontinuation of rifampicin or rifapentine. The serum concentrations of voriconazole at steady-state were monitored. Data on demographic characteristics and the serum voriconazole levels were used for statistical analyses.

Results

A total of 124 serum voriconazole concentrations from 109 patients were included in the study. The average serum concentration of voriconazole fell below the effective therapeutic range in patients treated with both voriconazole and rifampicin or rifapentine. Notably the co-administration of rifapentine led to a substantial (>70%) decrease in serum voriconazole levels in two patients. Moreover, this interfering effect persisted for at least 7 days following rifampicin discontinuation, while it endured for 5 days or more after discontinuation of rifapentine.

Conclusion

Concomitant use of voriconazole and rifampicin or rifapentine should be avoided, and it is not recommended to initiate voriconazole therapy within 5 or 7 days after discontinuation of rifapentine or rifampicin. Therapeutic drug monitoring not only provides a basis for the adjustment of clinical dose, but also serves as a valuable tool for identifying drug interactions.

Analytical and Clinical Validation of Assays for Volumetric Absorptive Microsampling (VAMS) of Drugs in Different Blood Matrices: A Literature Review

Volumetric absorptive microsampling (VAMS) is the newest and most promising sample-collection technique for quantitatively analyzing drugs, especially for routine therapeutic drug monitoring (TDM) and pharmacokinetic studies. This technique uses an absorbent white tip to absorb a fixed volume of a sample (10-50 µL) within a few seconds (2-4 s), is more flexible, practical, and more straightforward to be applied in the field, and is probably more cost-effective than conventional venous sampling (CVS). After optimization and validation of an analytical method of a drug taken by VAMS, a clinical validation study is needed to show that the results by VAMS can substitute what is gained from CVS and to justify implementation in routine practice. This narrative review aimed to assess and present studies about optimization and analytical validation of assays for drugs taken by VAMS, considering their physicochemical drug properties, extraction conditions, validation results, and studies on clinical validation of VAMS compared to CVS. The review revealed that the bio-analysis of many drugs taken with the VAMS technique was optimized and validated. However, only a few clinical validation studies have been performed so far. All drugs that underwent a clinical validation study demonstrated good agreement between the two techniques (VAMS and CVS), but only by Bland-Altman analysis. Only for tacrolimus and mycophenolic acid were three measurements of agreement evaluated. Therefore, VAMS can be considered an alternative to CVS in routine practice, especially for tacrolimus and mycophenolic acid. Still, more extensive clinical validation studies need to be performed for other drugs.

IFISTRATEGY: Spanish National Survey of Invasive Fungal Infection in Hemato-Oncologic Patients

Recent advances in the treatment of hematologic malignancies have improved the overall survival rate, but the number of patients at risk of developing an invasive fungal infection (IFI) has increased. Invasive infections caused by non-Candida albicans species, non-Aspergillus molds, and azole-resistant Aspergillus fumigatus have been increasingly reported in recent years. We developed a cross-sectional multicenter survey which involved a total of 55 hematologists and infectious disease specialists from a total of 31 Spanish hospitals, to determine the most frequent strategies used for the management of IFIs. Data collection was undertaken through an online survey which took place in 2022. Regarding key strategies, experts usually prefer early treatment for persistent febrile neutropenia, switching to another broad-spectrum antifungal family if azole-resistant Aspergillus is suspected, broad-spectrum azoles and echinocandins as prophylactic treatment in patients receiving midostaurin or venetoclax, and liposomal amphotericin B for breakthrough IFIs after prophylaxis with echinocandins in patients receiving new targeted therapies. For antifungals failing to reach adequate levels during the first days and suspected invasive aspergillosis, the most appropriate strategy would be to associate an antifungal from another family.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Application of Population Pharmacokinetic Analysis to Characterize CYP2C19 Mediated Metabolic Mechanism of Voriconazole and Support Dose Optimization

Purpose: The aims of this study were to establish a joint population pharmacokinetic model for voriconazole and its N-oxide metabolite in immunocompromised patients, to determine the extent to which the CYP2C19 genetic polymorphisms influenced the pharmacokinetic parameters, and to evaluate and optimize the dosing regimens using a simulating approach.

Methods: A population pharmacokinetic analysis was conducted using the Phoenix NLME software based on 427 plasma concentrations from 78 patients receiving multiple oral doses of voriconazole (200 mg twice daily). The final model was assessed by goodness of fit plots, non-parametric bootstrap method, and visual predictive check. Monte Carlo simulations were carried out to evaluate and optimize the dosing regimens.

Results: A one-compartment model with first-order absorption and mixed linear and concentration-dependent-nonlinear elimination fitted well to concentration-time profile of voriconazole, while one-compartment model with first-order elimination well described the disposition of voriconazole N-oxide. Covariate analysis indicated that voriconazole pharmacokinetics was substantially influenced by the CYP2C19 genetic variations. Simulations showed that the recommended maintenance dose regimen would lead to subtherapeutic levels in patients with different CYP2C19 genotypes, and elevated daily doses of voriconazole might be required to attain the therapeutic range.

Conclusions: The joint population pharmacokinetic model successfully characterized the pharmacokinetics of voriconazole and its N-oxide metabolite in immunocompromised patients. The proposed maintenance dose regimens could provide a rationale for dosage individualization to improve clinical outcomes and minimize drug-related toxicities.

The Overview on the Pharmacokinetic and Pharmacodynamic Interactions of Triazoles

Second generation triazoles are widely used as first-line drugs for the treatment of invasive fungal infections, including aspergillosis and candidiasis. This class, along with itraconazole, voriconazole, posaconazole, and isavuconazole, is characterized by a broad range of activity, however, individual drugs vary considerably in safety, tolerability, pharmacokinetics profiles, and interactions with concomitant medications. The interaction may be encountered on the absorption, distribution, metabolism, and elimination (ADME) step. All triazoles as inhibitors or substrates of CYP isoenzymes can often interact with many drugs, which may result in the change of the activity of the drug and cause serious side effects. Drugs of this class should be used with caution with other agents, and an understanding of their pharmacokinetic profile, safety, and drug-drug interaction profiles is important to provide effective antifungal therapy. The manuscript reviews significant drug interactions of azoles with other medications, as well as with food. The PubMed and Google Scholar bases were searched to collect the literature data. The interactions with anticonvulsants, antibiotics, statins, kinase inhibitors, proton pump inhibitors, non-nucleoside reverse transcriptase inhibitors, opioid analgesics, benzodiazepines, cardiac glycosides, nonsteroidal anti-inflammatory drugs, immunosuppressants, antipsychotics, corticosteroids, biguanides, and anticoagulants are presented. We also paid attention to possible interactions with drugs during experimental therapies for the treatment of COVID-19.

Impact of CYP2C19 Phenotype and Drug-Drug Interactions on Voriconazole Concentration in Pediatric Patients

Voriconazole (VRC), a first-line agent for the treatment of invasive fungal infections, is mainly metabolized by human cytochrome P450 (CYP) 2C19. In this study, a retrospective analysis was performed to investigate the key factors that influence the plasma trough concentration (C_min) of VRC, and an appropriate dosing regimen for pediatric patients was drafted subsequently. Overall, factors such as age, CYP2C19 phenotype, and combination medication with proton pump inhibitors accounted for 23.4% of variability in dose-normalized C_min values of VRC by a multiple linear regression analysis. Dose-normalized C_min values in the poor metabolizers (PMs) and intermediate metabolizers (IMs) were significantly higher than those in extensive metabolizers (EMs) (P < 0.001). To achieve therapeutic C_min for CYP2C19 ultrarapid metabolizers (UMs) or EMs, patients aged no more than 12 and more than 12 years required doses of 6.53 ± 2.08 and 3.95 ± 0.85 mg/kg of body weight twice daily (P = 0.007). For CYP2C19 PMs or IMs, patients aged under 12 and over 12 years required doses of 5.75 ± 1.73 and 4.23 ± 0.76 mg/kg twice daily, respectively (P = 0.019). Furthermore, coadministration of rifamycin sodium or omeprazole exhibited significant effects on VRC C_min. Taken together, it is necessary to pay attention to the impact of CYP2C19 phenotype and drug-drug interactions to achieve optimal therapy.

Voriconazole-Induced Hepatotoxicity Resolved after Switching to Amphotericin B in Fusarium dimerum Central Line-Associated Bloodstream Infection

Patient: Female, 38-year-old

Final Diagnosis: Drug induced liver injury

Symptoms: Fever • abdominal pain • nausea and vomiting • loose stools

Medication: —

Clinical Procedure: —

Specialty: Infectious Diseases • General and Internal Medicine • Pharmacology and Pharmacy

Interactive Effects of Glucocorticoids and Cytochrome P450 Polymorphisms on the Plasma Trough Concentrations of Voriconazole

Aims: To explore the interactive influence of glucocorticoids and cytochrome P450 (CYP450) polymorphisms on voriconazole (VRC) plasma trough concentrations (C_min) and provide a reliable basis for reasonable application of VRC.

Methods: A total of 918 VRC C_min from 231 patients was collected and quantified using high-performance liquid chromatography in this study. The genotypes of CYP2C19, CYP3A4, and CYP3A5 were detected by DNA sequencing assay. The effects of different genotypes and the coadministration of glucocorticoids on VRC C_min were investigated. Furthermore, the interactive effects of glucocorticoids with CYP450s on VRC C_min were also analyzed.

Results: The median C_min of oral administration was lower than that of intravenous administration (1.51 vs. 4.0 mg l⁻¹). Coadministration of glucocorticoids (including dexamethasone, prednisone, prednisolone, and methylprednisolone) reduced the VRC C_min/dose, respectively, among which dexamethasone make the median of the VRC C_min/dose ratio lower. As a result, when VRC was coadministrated with glucocorticoids, the proportion of VRC C_min/dose in the subtherapeutic window was increased. Different CYP450 genotypes have different effects on the C_min/dose of VRC. Mutations of CYP2C19*2 and *3 increased C_min/dose of VRC, while CYP2C19*17 and CYP3A4 rs4646437 polymorphisms decreased C_min/dose of VRC. The mutation of CYP3A5 has no significant effect. Furthermore, CYP2C19*17 mutants could strengthen the effects of glucocorticoids and decrease VRC C_min/dose to a larger extent.

Conclusion: Our study revealed that glucocorticoids reduced the C_min/dose levels of VRC and different SNPs of CYP450 have different effects on the C_min/dose ratio of VRC. Glucocorticoids and CYP2C19*17 mutants had a synergistic effect on reducing VRC C_min/dose. The present results suggested that when VRC is combined with glucocorticoids, we should pay more attention to the clinical efficacy of VRC, especially when CYP2C19*17 mutants exist.

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

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

A multicentre prospective study evaluating the impact of proton-pump inhibitors omeprazole and pantoprazole on voriconazole plasma concentrations

Voriconazole is an antifungal metabolised by CYP2C19 enzyme, which can be inhibited by proton-pump inhibitors (PPIs). A prospective observational study was carried out to determine the influence of PPIs on voriconazole pharmacokinetic. The 78 patients included were divided into 4 groups: omeprazole (n = 32), pantoprazole (n = 25), esomeprazole (n = 3) and no PPI (n = 18). Patients with no PPI had no significant difference in plasma voriconazole concentration when compared with those with PPI (2.63 ± 2.13 μg/mL [95% confidence interval {CI} 1.57-3.69] vs 2.11 ± 1.73 μg/mL [95%CI 1.67-2.55], P > .05). However, voriconazole plasma concentration was significantly lower in patients treated with pantoprazole vs those treated with omeprazole (1.44 ± 1.22 μg/mL [95%CI 0.94-1.94) vs 2.67 ± 1.88 μg/mL [95%CI 2.02-3.32], P = .013) suggesting a greater CYP2C19 enzyme inhibitory effect of omeprazole. This study demonstrates the greater CYP inhibition capacity of omeprazole and should be helpful for the choice of PPIs for patients treated with voriconazole.

The utility of voriconazole therapeutic drug monitoring in a multi-racial cohort in Southeast Asia

OBJECTIVES

Voriconazole serum concentration, which is affected by several factors, is associated with treatment response and toxicity. There is paucity of data on voriconazole therapeutic drug monitoring (TDM) among Southeast Asians, who exhibit a higher prevalence of CYP2C19-poor metabolisers compared with Caucasians and East Asians. Hence, there are concerns for higher risk of voriconazole accumulation and toxicity. We aim to determine the utility of voriconazole TDM through establishing: (1) proportion of patients achieving therapeutic troughs without dose adjustments; (2) characterisation of patients with sub-therapeutic, therapeutic and supra-therapeutic levels; (3) appropriate dose titrations/dose required for therapeutic troughs; (4) correlation between troughs and adverse events, treatment response/fungal breakthrough.

PATIENTS AND METHODS

A single-centre retrospective analysis of data from adults (≥21 years old) with ≥1 voriconazole trough measured at Singapore General Hospital from 2015 to 2017 was performed.

RESULTS

Thirty-two patients (45.7%) among 70 patients achieved therapeutic troughs (defined as 2.0-5.5 mg/L) without dose adjustments. Eleven patients (15.7%) experienced hepatotoxicity (troughs 0.5 to >7.5 mg/L). Neurotoxicity occurred in three patients (4.3%) (troughs ≥6.7 mg/L) and all patients had symptom resolution upon dose reduction. Treatment failure of invasive fungal infection appeared less in patients with therapeutic troughs compared with sub-therapeutic troughs (11.4% vs. 14.2%). Two patients experienced treatment failure despite supra-therapeutic voriconazole troughs.

CONCLUSIONS

TDM should be implemented due to significant unpredictability in dose exposure. TDM can reduce unnecessary switches to alternatives due to intolerability and rule in the possibility of resistant organisms in the event of treatment failure despite therapeutic troughs, alerting clinicians to switch to alternatives promptly.

Voriconazole treatment in adults and children with hematological diseases: can it be used without measurement of plasma concentration?

Indication and timing of trough plasma-voriconazole (VCZ)-concentration (t-PVC) measurement during VCZ treatment is a debated issue. Patterns of t-PVC were prospectively evaluated in pediatric (50 courses) and adult (95 courses) hematologic patients. Efficacy patterns were defined: adequate, t-PVC always ≥1 mcg/ml; borderline, at least one t-PVC measurement <1 mcg/ml but median value of the measurements ≥1 mcg/ml; inadequate, median value of the measurements <1 mcg/ml. Toxicity patterns were defined: favorable, t-PVC always ≤5 mcg/ml; borderline, one or more t-PVC measurements >5 mcg/ml but median value of the measurements ≤5 mcg/ml; unfavorable, median value of the measurements >5 mcg/ml. In children and adults the mean t-PVCs were higher during intravenous treatments. The t-PVC efficacy pattern was adequate, borderline and inadequate in 48%, 12%, and 40% of courses, respectively, in children, and in 66.3%, 16.8%, and 16.8% of courses, respectively, in adults. Adequate efficacy pattern was more frequent in children with body weight above the median (≥25 kg) (OR 4.8; P = .011) and in adults with active hematological disease receiving intravenous therapy (OR 3.93; P = .006). Favorable toxicity pattern was more frequent in children receiving VCZ daily dosage below the median (<14 mg/kg) (OR 4.18; P = .027) and in adults with body weight below the median (<68 kg) (OR 0.22; P = .004). T-PVC measurement is generally needed, however, a non t-PVC guided approach may be considered in heavier adults receiving intravenous VCZ. The risk of supratherapeutic levels does not seem an absolute indication for t-PVC monitoring.

Breakthrough invasive fungal diseases in acute myeloid leukemia patients receiving mould active triazole primary prophylaxis after intensive chemotherapy: An Italian consensus agreement on definitions and management

In the attempt to establish definitions and provide shared approaches to breakthrough invasive fungal diseases (br-IFD) in acute myeloid leukemia (AML) patients submitted to intensive chemotherapy and receiving triazoles as mould active primary antifungal prophylaxis (MA-PAP), literature on br-IFD in AML patients receiving triazoles MA-PAP was reviewed and a Consensus Development Conference Project was convened. The following four candidate key-questions were generated and formed the set of questions of the present document: "definition of br-IFD," "diagnostic strategy during MA-PAP to detect br-IFD," "possible causes of MA-PAP failure," "management of br-IFD."

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Isavuconazole: Case Report and Pharmacokinetic Considerations

Invasive fungal disease (IFD) is one of the major causes of morbidity and mortality in immunocompromised patients. Voriconazole (VCZ) and posaconazole (PCZ) remain the most widely used antifungals for the prophylaxis and treatment of IFD. However, VCZ and PCZ are liable for drug-drug interactions and show a pharmacokinetic variability that requires therapeutic drug monitoring (TDM). Isavuconazole (IVZ) is a newest generation triazole antifungal approved for the treatment of invasive aspergillosis (IA) in adult patients and for the treatment of invasive mucormycosis in adult patients for whom treatment with amphotericin B is inappropriate. In clinical trials, IVZ showed linear pharmacokinetics and little or no evidence for interactions with other drugs. There is only modest evidence on IVZ pharmacokinetics and TDM in real-life settings. Here, we report on IVZ pharmacokinetics in a young adult with Ph chromosome-negative acute lymphoblastic leukemia (ALL) who developed a “probable” IA during induction chemotherapy. The patient was initially treated with VCZ, but she developed a severe hepatic toxicity that was associated to the high plasma levels of VCZ. Therefore, VCZ was discontinued and the patient was switched to IVZ. After a loading dose of IVZ, the patient remained on IVZ for 5 months while also receiving standard maintenance chemotherapy for ALL. At day 65 after the start of IVZ, the patient experienced a significant hepatic toxicity; however, no change in IVZ plasma concentrations was observed in the face of a concomitant administration of many other drugs (cancer drugs, antiemetics, other anti-infectives). Hepatic toxicity resolved after discontinuing maintenance chemotherapy but not IVZ. These results show that (i) IVZ plasma concentrations remained stable throughout and were not affected by concomitant ALL therapy, and (ii) there was no relation between IVZ plasma concentration and hepatic toxicity. Thus, in clinical practice IVZ may not require TDM.

Successful and safe long-term treatment of cerebral aspergillosis with high-dose voriconazole guided by therapeutic drug monitoring

We report the case of a patient who had cerebral aspergillosis after otorhinolaryngologic surgery and who was successfully and safely treated with high-dose voriconazole (200 mg q6h) for more than 1 year thanks to a TDM-guided approach coupled with pharmacological review and with genotyping of CYP2C19 polymorphisms. The findings support the idea that personalized medicine based on TDM coupled with the need of avoiding drug-drug interactions may be helpful for maximizing the net benefit (probability of efficacy vs. probability of adverse events) of voriconazole in the management of long-term treatment of cerebral aspergillosis.

Optimization of Voriconazole Therapy for the Treatment of Invasive Fungal Infections in Adults

Therapeutic concentrations of voriconazole in invasive fungal infections (IFIs) are ensured using a drug monitoring approach, which relies on attainment of steady-state pharmacokinetics. For voriconazole, time to reach steady state can vary from 5-7 days, not optimal for critically ill patients. We developed a population pharmacokinetic/pharmacodynamic model-based approach to predict doses that can maximize the net benefit (probability of efficacy-probability of adverse events) and ensure therapeutic concentrations, early on during treatment. The label-recommended 200 mg voriconazole dose resulted in attainment of targeted concentrations in ≥80% patients in the case of Candida spp. infections, as compared to only 40-50% patients, with net benefit ranging from 5.8-61.8%, in the case of Aspergillus spp. infections. Voriconazole doses of 300-600 mg were found to maximize the net benefit up to 51-66.7%, depending on the clinical phenotype (due to CYP2C19 status and pantoprazole use) of the patient and type of Aspergillus infection.

The impact of proton pump inhibitors on the pharmacokinetics of voriconazole in vitro and in vivo

Voriconazole (VRC) and proton pump inhibitors (PPIs) have similar metabolic pathways. The objectives of the study are to evaluate the impact of PPIs on the pharmacokinetics of VRC. Human liver microsomes model was applied to assess the inhibitory effects of PPIs on the metabolism of VRC in vitro. A retrospective study was also carried out to explore the relationship between the plasma VRC trough concentrations and PPIs uses. Patients were divided into six groups: control (n = 166), lansoprazole (LAN, n = 38), esomeprazole (ESO, n = 19), omeprazole (OME, n = 45), pantoprazole (PAN, n = 43), and ilaprazole (ILA, n = 38) groups. All five PPIs showed concentration-dependent inhibitory effects on the VRC metabolism in human liver microsomes, among which LAN, OME and ESO were three of the most potent inhibitors. Consistently, co-administered with LAN, OME and ESO significantly increased the plasma VRC trough levels (p <  0.05), whereas there was no significant association between VRC concentrations and PAN or ILA use. Interestingly, patients in the PPIs groups were more likely to reach the therapeutic VRC range of 1-5.5 μg/mL in steady state when compared with control patients (75-81% VS 69%). In conclusion, although all PPIs showed inhibitory effects on the VRC metabolism in vitro, only LAN, OME and ESO significantly increased VRC plasma concentrations. This study should be helpful for choice of the type of PPIs for patients administered with VRC.

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.

Significant drug interaction between voriconazole and dexamethasone: A case report

BACKGROUND

Voriconazole is extensively metabolized by the CYP450 isoenzymes 2C19 and 3A4 and to a lesser extent by CYP2C9; therefore, any medication that affects this pathway can alter its plasma concentration. Treatment failure can probably occur if subtherapeutic levels are achieved.

CASE DESCRIPTION

A 32-year-old woman who suffered from acute lymphoblastic leukemia was admitted and received treatment with vincristine and dexamethasone. After several days, to control her fever, based on two consecutive positive serum galactomannan test results, voriconazole as an antifungal agent was added to Aspergillus infection treatment. Through the first week after voriconazole initiation, its plasma concentrations were subtherapeutic. The most suspicious medication for interaction was dexamethasone, which can induce CYP450 isoenzymes and reduce plasma concentration.

CONCLUSION

As a result of the narrow therapeutic window of voriconazole and the relationship between efficacy and plasma concentration of azoles, therapeutic drug monitoring of voriconazole in patients receiving a high dose of glucocorticoids is recommended, in order to achieve optimal response to treatment and toxicity reduction. Further studies regarding the interaction between voriconazole and dexamethasone to prevent clinically relevant interactions should be considered.

Determination of voriconazole and co-administered drugs in plasma of pediatric cancer patients using UPLC-MS/MS: A key step towards personalized therapeutics

Untreated invasive aspergillosis results in high mortality rate in pediatric cancer patients. Voriconazole (VORI), the first line of treatment, requires strict dose monitoring because of its narrow therapeutic index and individual variation in plasma concentration levels. Commonly co-administered drugs; either Esomeprazole (ESO) or Ondansetron (OND) have reported drug-drug interaction with VORI that should adversely alter therapeutic outcomes of the latter. Although VORI, ESO and OND are co-administered to pediatric cancer patients, the combined effect of ESO and OND on the plasma concentration levels of VORI has not been fully explored. In this study, an accurate, reliable and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated for simultaneous determination of VORI, ESO, and OND in ultra-low sample volumes (25 μL) of plasma of pediatric cancer patients. Based on the physicochemical properties of the studied drugs and internal standard, liquid-liquid extraction was successfully adopted with methyl t-butyl ether. Consistent and reproducible recovery of the three drugs and the internal standard were calculated using plasma and matrix matched samples (RE% > 72.97%, RSD < 8.29%). Chromatographic separation was carried out using UPLC with C18 column and a mobile phase of acetonitrile:water:methanol (70:25:5 V/V/V) at 0.3 mL/min. Mass spectrometric determination at positive electrospray ionization in the MRM mode was employed. The analysis was achieved within 4 min over a linear concentration range of 1.00-200.00 ng/mL for the three drugs. The assay validity was assessed as per the Food and Drug Administration guidelines for bioanalytical method validation, and satisfactory results were obtained. The accuracy and precision were within the acceptable limits for the three drugs in both quality control and incurred plasma samples. Matrix effect and process efficiency were investigated in neat solvent, post-extraction matrix, and plasma. Correlation of the plasma concentration levels of the three drugs revealed differences from the reported drug-drug interactions. This confirmed the need for simultaneous determination of VORI and co-administered drugs in order to achieve optimal therapeutic outcomes. To achieve this, analysis results of this study, genetic polymorphisms in CYP2C19 and clinical data will be used to establish one model incorporating all possible factors that might lead to variation in therapeutic outcomes.

A new cause of false positive voriconazole levels: Watch your collection tubes!

We communicate the interference of a compound of the blood collection tube with the accuracy of a validated high-pressure liquid chromatography method with ultraviolet detection for quantifying voriconazole levels, which led to false positive results. This could have serious consequences for patient management. Our advice is to implement external assessment programs.

Impact of the CYP2C19 genotype on voriconazole exposure in adults with invasive fungal infections

OBJECTIVES

Voriconazole, a first-line agent for the treatment of invasive fungal infections (IFIs), is metabolized by CYP2C19. A significant proportion of patients fail to achieve therapeutic trough concentrations with standard weight-based voriconazole dosing, placing them at increased risk for treatment failure, which can be life threatening. We sought to test the association between the CYP2C19 genotype and subtherapeutic voriconazole concentrations in adults with IFIs.

PATIENT AND METHODS

Adults receiving weight-based voriconazole dosing for the treatment of IFIs were genotyped for the CYP2C19*2, *3, and *17 polymorphisms, and CYP2C19 metabolizer phenotypes were inferred. Steady-state voriconazole trough plasma concentrations and the prevalence of subtherapeutic troughs (<2 mg/l) were compared between patients with the CYP2C19*17/*17 (ultrarapid metabolizer, UM) or *1/*17 (rapid metabolizer, RM) genotype versus those with other genotypes. Logistic regression, adjusting for clinical factors, was performed to estimate the odds of subtherapeutic concentrations.

RESULTS

Of 70 patients included (mean age 52.5±18 years), 39% were RMs or UMs. Compared with patients with the other phenotypes, RMs/UMs had a lower steady-state trough concentration (4.26±2.2 vs. 2.86±2.3, P=0.0093) and a higher prevalence of subtherapeutic troughs (16 vs. 52%, P=0.0028), with an odds ratio of 5.6 (95% confidence interval: 1.64-19.24, P=0.0044).

CONCLUSION

Our findings indicate that adults with the CYP2C19 RM or UM phenotype are more likely to have subtherapeutic concentrations with weight-based voriconazole dosing. These results corroborate previous findings in children and support the potential clinical utility of CYP2C19 genotype-guided voriconazole dosing to avoid underexposure in RMs and UMs.

Methimazole-induced liver injury overshadowed by methylprednisolone pulse therapy: Case report

RATIONALE

Treatment choices are limited, when deciding how to manage thyrotoxicosis and moderate to severe Graves ophthalmopathy (GO) with suspected optic nerve damage in patients with elevated liver transaminase levels. The situation become even more complicated, if methimazole induced hepatotoxicity is suspected and intravenous methylprednisolone is co-administrated.

PATIENT CONCERNS

A 74-year-old woman presented with spontaneous retro-bulbar pain, eyelid swelling and inconstant diplopia.

DIAGNOSES

Thyrotoxicosis and severe GO with suspected optic nerve damage and drug induced liver injury (DILI).

INTERVENTIONS

Intravenous methylprednisolone pulse therapy was administered to treat GO and methimazole was continued for thyrotoxicosis. Dose of methimazole was reduced after exclusion of concurrent infection and active liver disease.

OUTCOMES

The GO symptoms (eyelid swelling, sight loss, proptosis, retro-bulbar pain, diplopia) markedly decreased after the treatment course. Liver transaminases spontaneously returned to normal ranges and remained normal during the next 12 months until the Graves' disease until the treatment was completed.

LESSONS

1. The interaction of methimazole and methylprednisolone may result in DILI. 2. In a patient without concomitant liver diseases MP can be continued if the methimazole dose is reduced if no other treatment options are available.

The influence of combination use of CYP450 inducers on the pharmacokinetics of voriconazole: a systematic review

WHAT IS KNOWN AND OBJECTIVES

Voriconazole is a triazole antifungal agent and is extensively metabolized via cytochrome P450 (CYP450); therefore, special precautions need to be taken when co-administered with a known CYP450 inducer, which may lead to treatment failure. The influence of some CYP450 inducers on the pharmacokinetics of voriconazole has been described in previous studies, but a systematic review was lacking. In this study, we carried out a systematic review to assess the influence of CYP450 inducers on the pharmacokinetic (PK) parameters of voriconazole.

METHODS

Pubmed, Embase, Cochrane Library, Clinicaltrials.gov and three Chinese databases (CNKI, CBM and WanFang) were searched through January 2016. Interventional and observational studies comparing the PK parameters of voriconazole used alone or with CYP450 inducers in healthy volunteers and patients were included. The outcomes included were the area under the plasma concentration-time curve (AUC), peak plasma concentrations (C_max ) and trough plasma concentrations (C_min ). The quality of the included studies was assessed using Cochrane's risk of bias tool, Newcastle-Ottawa Scale (NOS) and a modified risk of bias tool for pharmacokinetic before-and-after studies.

RESULTS AND DISCUSSION

Sixteen studies were included in this review: three randomized controlled trials (RCTs), five single-arm before-after studies (SBAs), six cohort studies and two case reports. All studies except case reports had moderate to high quality. Of the 11 inducers reviewed, efavirenz, ritonavir (chronic use), phenytoin, rifampin and rifabutin significantly decreased mean AUC and C_max of voriconazole; St John's wort significantly decreased only mean AUC; rifampin, rifabutin, phenobarbital and carbamazepine significantly decreased mean C_min . Etravirine and Ginkgo biloba did not reveal any such influence. The influence of glucocorticoids may depend on its type and dose.

WHAT IS NEW AND CONCLUSIONS

To conclude, the combination use of high-dose efavirenz, high-dose ritonavir, St John's wort, rifampin, phenobarbital, or carbamazepine with voriconazole is contraindicated as instructed in the drug label. Low-dose efavirenz, low-dose ritonavir, rifabutin and phenytoin may be used together with voriconazole provided TDM and dose adjustment of voriconazole. Moreover, this study shows there is low risk of drug-drug interactions when voriconazole is co-administered with etravirine or G. biloba; however, whether the use of glucocorticoids has a clinically significant effect on voriconazole still requires more evidence. This study also highlights the lack of clinical studies and future high-quality studies assessing the influence of CYP450 inducers on voriconazole. PK parameters and dosing optimization should be designed to provide a more definitive answer regarding the necessity of TDM and the recommendations for dose adjustment of voriconazole.

Different effects of lansoprazole and rabeprazole on the plasma voriconazole trough levels in allogeneic hematopoietic cell transplant recipients

Voriconazole (VRC) is widely used as prophylaxis and in the treatment of invasive fungal disease (IFD) after allogeneic hematopoietic cell transplantation (HCT). We retrospectively examined the results of VRC therapeutic drug monitoring (TDM) in allogeneic HCT recipients. A total of 474 samples were obtained from 59 adult patients who received VRC during the first 100 days following HCT between 2009 and 2014 in our institute. Seventeen patients received VRC for prophylaxis of IFD, and 42 received VRC for the empirical or preemptive therapy for IFD. A total of 299 samples (63 %) were obtained during the administration of the intravenous form of VRC. The median VRC daily dose based on the actual body weight was 6.68 mg/kg/day (range, 1.92-10.41 mg/kg/day). The median VRC trough level was 0.99 mg/l (range, <0.09-5.45 mg/l). The multivariate analysis using a logistic regression model demonstrated significantly higher VRC trough levels (≥1.0 mg/l) in males (P < 0.001), empirical or preemptive therapy (P = 0.002), VRC daily dose based on the actual body weight ≥7 mg/kg/day (P < 0.001), and concomitant use of lansoprazole as compared to rabeprazole (P < 0.001). The concomitant use of calcineurin inhibitors and corticosteroids had no effects on VRC trough levels in multivariate analysis. These data suggest that lansoprazole and rabeprazole have different effects on the plasma VRC trough levels in the allogeneic HCT recipients.

Subtherapeutic voriconazole concentrations associated with concomitant dexamethasone: case report and review of the literature

WHAT IS KNOWN AND OBJECTIVE

Voriconazole has significant drug interactions due to metabolism by CYP enzymes. Subtherapeutic voriconazole concentrations associated with concomitant dexamethasone are not well described.

CASE DESCRIPTION

An 84-year-old male was started on voriconazole for a fungal brain abscess. He was readmitted due to clinical failure thought to be the result of subtherapeutic voriconazole concentrations. Dexamethasone was identified as a potential cause due to its induction of CYP enzymes. This interaction was substantiated by sequential troughs that demonstrated a rise in voriconazole concentrations as dexamethasone was tapered off.

WHAT IS NEW AND CONCLUSION

Therapeutic drug monitoring for patients on voriconazole and dexamethasone is essential to prevent suboptimal clinical outcomes.

CNS infections in patients with hematological disorders (including allogeneic stem-cell transplantation)-Guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO)

Diagnosis of CNS infections remains a great challenge in patients with hematological disorders since symptoms might both be masked and be mimicked by other conditions such as metabolic disturbances or consequences from antineoplastic treatment. Thus, awareness of this complication is crucial and any suspicion of a CNS infection should lead to timely and adequate diagnostics and treatment to improve the outcome in this population.

Infections of the central nervous system (CNS) are infrequently diagnosed in immunocompetent patients, but they do occur in a significant proportion of patients with hematological disorders. In particular, patients undergoing allogeneic hematopoietic stem-cell transplantation carry a high risk for CNS infections of up to 15%. Fungi and Toxoplasma gondii are the predominant causative agents. The diagnosis of CNS infections is based on neuroimaging, cerebrospinal fluid examination and biopsy of suspicious lesions in selected patients. However, identification of CNS infections in immunocompromised patients could represent a major challenge since metabolic disturbances, side-effects of antineoplastic or immunosuppressive drugs and CNS involvement of the underlying hematological disorder may mimic symptoms of a CNS infection. The prognosis of CNS infections is generally poor in these patients, albeit the introduction of novel substances (e.g. voriconazole) has improved the outcome in distinct patient subgroups. This guideline has been developed by the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO) with the contribution of a panel of 14 experts certified in internal medicine, hematology/oncology, infectious diseases, intensive care, neurology and neuroradiology. Grades of recommendation and levels of evidence were categorized by using novel criteria, as recently published by the European Society of Clinical Microbiology and Infectious Diseases.