The pharmacokinetics and safety of intravenous voriconazole - a novel wide-spectrum antifungal agent

A Physiologically Based Pharmacokinetic Model of Voriconazole in Human CNS -- Integrating Time-Dependent Inhibition of CYP3A4, Genetic Polymorphisms of CYP2C19 and Possible Transporter Mechanisms

AIMS

Voriconazole is a classical antifungal drug that is often used to treat CNS fungal infections due to its permeability through the BBB. However, its clinical use remains challenging because of its narrow therapeutic window and wide inter-individual variability. In this study, we proposed an optimized and validated PBPK model by integrating in vitro, in vivo and clinical data to simulate the distribution and PK process of voriconazole in the CNS, providing guidance for clinical individualized treatment.

METHODS

The model structure was optimized and tissue-to-plasma partition coefficients were obtained through animal experiments. Using the allometric relationships, the distribution of voriconazole in the human CNS was predicted. The model integrated factors affecting inter-individual variation and drug interactions of voriconazole-polymorphisms in the CYP2C19 gene and auto-inhibition and then was validated using real clinical data.

RESULTS

The overall AFE value showing model predicted differences was 1.1420 in the healthy population; and in the first prediction of plasma and CSF in actual clinical patients, 89.5% of the values were within the 2-fold error interval, indicating good predictive performance of the model. The bioavailability of voriconazole varied at different doses (39%-86%), and the optimized model conformed to this pattern (46%-83%).

CONCLUSION

Combined with the relevant pharmacodynamic indexes, the PBPK model provides a feasible way for precise medication in patients with CNS infection and improve the treatment effect and prognosis.

Efficacy and safety of voriconazole in the treatment of invasive pulmonary aspergillosis in patients with liver failure: study protocol for a randomized controlled clinical trial

BACKGROUND

Acute-on-chronic liver failure (ACLF) is a common clinical type of liver failure, and patients with acute-on-chronic liver failure are prone to fungal infections, especially the increasing incidence of invasive pulmonary aspergillosis (IPA). Voriconazole is recommended as the first-line antifungal agent in the treatment of invasive aspergillosis; however, no recommendation has been given for patients with severe liver cirrhosis (Child-Pugh C) and liver failure. This trial aims to examine the therapeutic effects and safety of voriconazole in the treatment of IPA in patients with liver failure.

METHODS

This study is a non-double-blind randomized controlled trial. The 96 eligible acute-on-chronic liver failure patients complicated with invasive pulmonary aspergillosis will be randomly assigned to receive either the optimized voriconazole regimen or the recommended voriconazole regimen for patients with mild to moderate liver cirrhosis (Child-Pugh A and B), at a 1:1 ratio, with an 8-week follow-up period. The antifungal efficacy of voriconazole will be the primary outcome measure. Plasma voriconazole trough concentration, the laboratory examination (CRP, PCT, ESR, etc.), chest CT, adverse events, and mortality at week 4 and 8 will be the secondary outcome measures.

DISCUSSION

This trial aims to demonstrate the efficacy and safety of voriconazole in the treatment of IPA in patients with liver failure, which is expected to provide a reference for scientific optimization of voriconazole regimens and a realistic basis for the standardized treatment of acute-on-chronic liver failure patients complicated with invasive pulmonary aspergillosis.

TRIAL REGISTRATION

The trial was registered with the Chinese Clinical Trial Registry, ChiCTR2100048259. Registered on 5 July 2021.

Optimal timing for therapeutic drug monitoring of voriconazole to prevent adverse effects in Japanese patients

BACKGROUND

The optimal timing for therapeutic drug monitoring (TDM) of voriconazole in Asians, who have higher rates of poor metabolisers than non-Asians, is unclear. This can cause unexpectedly high concentrations and delays in reaching steady-state levels.

OBJECTIVES

To determine the appropriate timing of TDM in Japanese patients receiving voriconazole.

PATIENTS/METHODS

Trough levels (Cmin ) were measured on days 3-5 (recommended timing, RT) and days 6-14 (delayed timing, DT) after starting voriconazole in patients receiving an appropriate dosage. Considering bioavailability, Cmin was only compared in patients receiving oral voriconazole.

RESULTS

A total of 289 and 186 patients were included in the safety and pharmacokinetic analyses, respectively. There was a significant difference in Cmin measured no later than and after day 5 (3.59 ± 2.12 [RT] vs. 4.77 ± 3.88 μg/mL [DT], p = .023), whereas no significant difference was observed on cutoff day 6 (3.91 ± 2.60 vs. 4.40 ± 3.94 μg/mL, p = .465), suggesting that Cmin close to the steady-state was achieved after day 5. DT causes a delay in achieving the therapeutic range. The hepatotoxicity rates were 21.5% and 36.8% in the RT and DT groups, respectively (p = .004); DT was an independent risk factor for hepatotoxicity.

CONCLUSION

Although steady-state concentrations may not be achieved by day 5, early dose optimisation using RT can prevent hepatotoxicity in Japanese patients. TDM should be performed on days 3-5 to ensure safety. However, subsequent TDM may be necessary due to a possible further increase in Cmin .

Physicochemical Characteristics of Antimicrobials and Practical Recommendations for Intravenous Administration: A Systematic Review

Most antimicrobial drugs need an intravenous (IV) administration to achieve maximum efficacy against target pathogens. IV administration is related to complications, such as tissue infiltration and thrombo-phlebitis. This systematic review aims to provide practical recommendations about diluent, pH, osmolarity, dosage, infusion rate, vesicant properties, and phlebitis rate of the most commonly used antimicrobial drugs evaluated in randomized controlled studies (RCT) till 31 March 2023. The authors searched for available IV antimicrobial drugs in RCT in PUBMED EMBASE®, EBSCO® CINAHL®, and the Cochrane Controlled Clinical trials. Drugs' chemical features were searched online, in drug data sheets, and in scientific papers, establishing that the drugs with a pH of <5 or >9, osmolarity >600 mOsm/L, high incidence of phlebitis reported in the literature, and vesicant drugs need the adoption of utmost caution during administration. We evaluated 931 papers; 232 studies were included. A total of 82 antimicrobials were identified. Regarding antibiotics, 37 reach the "caution" criterion, as well as seven antivirals, 10 antifungals, and three antiprotozoals. In this subgroup of antimicrobials, the correct vascular access device (VAD) selection is essential to avoid complications due to the administration through a peripheral vein. Knowing the physicochemical characteristics of antimicrobials is crucial to improve the patient's safety significantly, thus avoiding administration errors and local side effects.

Trends in Implementation of Loading Dose of Voriconazole from 2010 to 2019 and Influencing Factors of Loading Dose Based on a Japanese Administrative Claim Database: A Retrospective Cohort Study

A loading dose of voriconazole (VRCZ) is recommended to increase its blood concentration at an early stage. However, the trends in the implementation of the loading dose in VRCZ in Japan has not yet been clarified. In addition, although pharmacists play many important roles in antimicrobial stewardship, the effect of pharmacist intervention on the implementation of a loading dose of VRCZ has not yet been reported. Therefore, this study aimed to clarify the implementation of loading dose of VRCZ and the influencing factors of loading dose. This study used an administrative claims database that included patients who received injectable VRCZ between 2010 and 2019. The implementation of loading doses in the VRCZ was evaluated annually. Multivariate logistic regression analysis was performed to identify the factors influencing loading dose. Overall, 2197 patients were included. The implementation rate of the loading dose remained below 65% throughout the study period. Among medical fees that can be calculated through pharmacist intervention, only the infection prevention and control premium significantly increased the implementation of loading dose of VRCZ (odds ratio: 1.587, 95% confidence interval: 1.053-2.392). In conclusion, antifungal stewardship may have been promoted at medical institutions that established infection prevention and control. In the future, pharmacists will need to intervene more actively from the beginning of VRCZ administration.

The Application of Hollow Fiber Cartridge in Biomedicine

The hollow fiber cartridge has the advantages of good semi-permeability, high surface area to volume ratio, convenient operation, and so on. Its application in chemical analysis, drug in vitro experiment, hemodialysis, and other fields has been deeply studied. This paper introduces the basic structure of hollow fiber cartridge, compares the advantages and disadvantages of a hollow fiber infection model constructed by a hollow fiber cartridge with traditional static model and animal infection model and introduces its application in drug effects, mechanism of drug resistance, and evaluation of combined drug regimen. The principle and application of hollow fiber bioreactors for cell culture and hollow fiber dialyzer for dialysis and filtration were discussed. The hollow fiber cartridge, whether used in drug experiments, artificial liver, artificial kidney, etc., has achieved controllable experimental operation and efficient and accurate experimental results, and will provide more convenience and support for drug development and clinical research in the future.

Updates in the Pharmacologic Prophylaxis and Treatment of Invasive Candidiasis in the Pediatric and Neonatal Intensive Care Units

Purpose of review

The goal of this review was to provide an update on the prevention and treatment options for invasive candidiasis (IC) in the neonatal intensive care unit (NICU) and pediatric intensive care unit (PICU).

Recent findings

Studies have further validated the use of fluconazole for IC prophylaxis among high-risk patients in the NICU. It remains unclear if prophylaxis leads to resistance development and the ideal dosage regimen is still not clear. Recent studies have been published comparing caspofungin and micafungin to amphotericin B and illustrated similar efficacy outcomes in the NICU. Micafungin now has approval from the United States Food and Drug Administration (FDA) for use in infants < 4 months of age. Prophylactic strategies in the PICU could include zinc and vitamin D. Anidulafungin has recent non-comparative data supporting use in pediatric patients older than 1 month of age and also has a recent FDA approval for use in children 1 month of age and older.

Summary

Fluconazole prophylaxis remains a reasonable strategy in select NICU patients, although further analyses of resistance and the optimal dosage regimen are needed. Echinocandins are potential therapeutic options for non-meningitis or urinary tract infections in both the neonatal and pediatric population.

Voriconazole efficacy against Candida glabrata and Candida krusei: preclinical data using a validated in vitro pharmacokinetic/pharmacodynamic model

BACKGROUND

Voriconazole exhibits in vitro activity against Candida glabrata and Candida krusei (EUCAST/CLSI epidemiological cut-off values 1/0.25 and 1/0.5 mg/L, respectively). Yet, EUCAST found insufficient evidence to set breakpoints for these species. We explored voriconazole pharmacodynamics (PD) in an in vitro dynamic model simulating human pharmacokinetics (PK).

METHODS

Four C. glabrata and three C. krusei isolates (voriconazole EUCAST and CLSI MICs of 0.03-2 mg/L) were tested in the PK/PD model simulating voriconazole exposures (t½ ∼6 h q12h dosing for 3 days). PK/PD breakpoints were determined calculating the PTA for exposure indices fAUC0-24/MIC associated with half-maximal activity (EI50) using Monte Carlo simulation analysis.

RESULTS

Fungal load increased from 3.60±0.35 to 8.41±0.24 log10 cfu/mL in the drug-free control, with a maximum effect of ∼1 log10 kill of C. glabrata and C. krusei isolates with MICs of 0.06 and 0.25 mg/L, respectively, at high drug exposures. The 72 h log10 cfu/mL change versus fAUC0-24/MIC relationship followed a sigmoid curve for C. glabrata (R2=0.85-0.87) and C. krusei (R2=0.56-0.76) with EI50 of 49 (32-76) and 52 (33-78) fAUC/MIC for EUCAST and 55 (31-96) and 80 (42-152) fAUC/MIC for CLSI, respectively. The PTAs for C. glabrata and C. krusei isolates with EUCAST/CLSI MICs ≤0.125/≤0.06 mg/L were >95%. Isolates with EUCAST/CLSI MICs of 0.25-1/0.125-0.5 would require trough levels 1-4 mg/L; isolates with higher MICs would not attain the corresponding PK/PD targets without reaching toxicity.

CONCLUSIONS

The in vitro PK/PD breakpoints for C. glabrata and C. krusei for EUCAST (0.125 mg/L) and CLSI (0.06 mg/L) bisected the WT populations. Trough levels of >4 mg/L, which are not clinically feasible, are necessary for efficacy against WT isolates.

Application of a Physiologically Based Pharmacokinetic Model to Characterize Time-dependent Metabolism of Voriconazole in Children and Support Dose Optimization

Background: Voriconazole is a potent antifungal drug with complex pharmacokinetics caused by time-dependent inhibition and polymorphisms of metabolizing enzymes. It also exhibits different pharmacokinetic characteristics between adults and children. An understanding of these alterations in pharmacokinetics is essential for pediatric dose optimization. Objective: To determine voriconazole plasma exposure in the pediatric population and further investigate optimal dosage regimens. Methods: An adult and pediatric physiologically based pharmacokinetic (PBPK) model of voriconazole, integrating auto-inhibition of cytochrome P450 3A4 (CYP3A4) and CYP2C19 gene polymorphisms, was developed. The model was evaluated with visual predictive checks and quantitative measures of the predicted/observed ratio of the area under the plasma concentration-time curve (AUC) and maximum concentration (Cmax). The validated pediatric PBPK model was used in simulations to optimize pediatric dosage regimens. The probability of reaching a ratio of free drug (unbound drug concentration) AUC during a 24-h period to minimum inhibitory concentration greater than or equal to 25 (fAUC24h/MIC ≥ 25) was assessed as the pharmacokinetic/pharmacodynamic index. Results: The developed PBPK model well represented voriconazole's pharmacokinetic characteristics in adults; 78% of predicted/observed AUC ratios and 85% of Cmax ratios were within the 1.25-fold range. The model maintained satisfactory prediction performance for intravenous administration in pediatric populations after incorporating developmental changes in anatomy/physiology and metabolic enzymes, with all predicted AUC values within 2-fold and 73% of the predicted Cmax within 1.25-fold of the observed values. The simulation results of the PBPK model suggested that different dosage regimens should be administered to children according to their age, CYP2C19 genotype, and infectious fungal genera. Conclusion: The PBPK model integrating CYP3A4 auto-inhibition and CYP2C19 gene polymorphisms successfully predicted voriconazole pharmacokinetics during intravenous administration in children and could further be used to optimize dose strategies. The infectious fungal genera should be considered in clinical settings, and further research with large sample sizes is required to confirm the current findings.

Effect of Therapeutic Drug Monitoring and Cytochrome P450 2C19 Genotyping on Clinical Outcomes of Voriconazole: A Systematic Review

Objectives

To examine current knowledge on the clinical utility of therapeutic drug monitoring (TDM) in voriconazole therapy, the impact of CYP2C19 genotype on voriconazole plasma concentrations, and the role of CYP2C19 genotyping in voriconazole therapy.

Data Sources

Three literature searches were conducted for original reports on (1) TDM and voriconazole outcomes and (2) voriconazole and CYP2C19 polymorphisms. Searches were conducted through EMBASE, MEDLINE/PubMed, Scopus, and Cochrane Central Register of Controlled Trials from inception to June 2020.

Study Selection and Data Extraction

Randomized controlled trials, cohort studies, and case series with ≥10 patients were included. Only full-text references in English were eligible.

Data Synthesis

A total of 63 studies were reviewed. TDM was recommended because of established concentration and efficacy/toxicity relationships. Voriconazole trough concentrations ≥1.0 mg/L were associated with treatment success; supratherapeutic concentrations were associated with increased neurotoxicity; and hepatotoxicity associations were more prevalent in Asian populations. CYP2C19 polymorphisms significantly affect voriconazole metabolism, but no relationship with efficacy/safety were found. Genotype-guided dosing with TDM was reported to increase chances of achieving therapeutic range.

Relevance to Patient Care and Clinical Practice

Genotype-guided dosing with TDM is a potential solution to optimizing voriconazole efficacy while avoiding treatment failures and common toxicities.

Conclusions

Voriconazole plasma concentrations and TDM are treatment outcome predictors, but research is needed to form a consensus target therapeutic range and dosage adjustment guidelines based on plasma concentrations. CYP2C19 polymorphisms are a predictor of voriconazole concentrations and metabolism, but clinical implications are not established. Large-scale, high-methodological-quality trials are required to investigate the role for prospective genotyping and establish CYP2C19-guided voriconazole dosing recommendations.

Saliva for Precision Dosing of Antifungal Drugs: Saliva Population PK Model for Voriconazole Based on a Systematic Review

Precision dosing for many antifungal drugs is now recommended. Saliva sampling is considered as a non-invasive alternative to plasma sampling for therapeutic drug monitoring (TDM). However, there are currently no clinically validated saliva models available. The aim of this study is firstly, to conduct a systematic review to evaluate the evidence supporting saliva-based TDM for azoles, echinocandins, amphotericin B, and flucytosine. The second aim is to develop a saliva population pharmacokinetic (PK) model for eligible drugs, based on the evidence. Databases were searched up to July 2019 on PubMed® and Embase®, and 14 studies were included in the systematic review for fluconazole, voriconazole, itraconazole, and ketoconazole. No studies were identified for isavuconazole, posaconazole, flucytosine, amphotericin B, caspofungin, micafungin, or anidulafungin. Fluconazole and voriconazole demonstrated a good saliva penetration with an average S/P ratio of 1.21 (± 0.31) for fluconazole and 0.56 (± 0.18) for voriconazole, both with strong correlation (r = 0.89-0.98). Based on the evidence for TDM and available data, population PK analysis was performed on voriconazole using Nonlinear Mixed Effects Modeling (NONMEM 7.4). 137 voriconazole plasma and saliva concentrations from 11 patients (10 adults, 1 child) were obtained from the authors of the included study. Voriconazole pharmacokinetics was best described by one-compartment PK model with first-order absorption, parameterized by clearance of 4.56 L/h (36.9% CV), volume of distribution of 60.7 L, absorption rate constant of 0.858 (fixed), and bioavailability of 0.849. Kinetics of the voriconazole distribution from plasma to saliva was identical to the plasma kinetics, but the extent of distribution was lower, modeled by a scale factor of 0.5 (4% CV). A proportional error model best accounted for the residual variability. The visual and simulation-based model diagnostics confirmed a good predictive performance of the saliva model. The developed saliva model provides a promising framework to facilitate saliva-based precision dosing of voriconazole.

Toward Harmonization of Voriconazole CLSI and EUCAST Breakpoints for Candida albicans Using a Validated In Vitro Pharmacokinetic/Pharmacodynamic Model

CLSI and EUCAST susceptibility breakpoints for voriconazole and Candida albicans differ by one dilution (≤0.125 and ≤0.06 mg/liter, respectively) whereas the epidemiological cutoff values for EUCAST (ECOFF) and CLSI (ECV) are the same (0.03 mg/liter). We therefore determined the pharmacokinetic/pharmacodynamic (PK/PD) breakpoints of voriconazole against C. albicans for both methodologies with an in vitro PK/PD model, which was validated using existing animal PK/PD data. Four clinical wild-type and non-wild-type C. albicans isolates (voriconazole MICs, 0.008 to 0.125 mg/liter) were tested in an in vitro PK/PD model. For validation purposes, mouse PK were simulated and in vitro PD were compared with in vivo outcomes. Human PK were simulated, and the exposure-effect relationship area under the concentration-time curve for the free, unbound fraction of a drug from 0 to 24 h (fAUC_0-24)/MIC was described for EUCAST and CLSI 24/48-h methods. PK/PD breakpoints were determined using the fAUC_0-24/MIC associated with half-maximal activity (EI₅₀) and Monte Carlo simulation analysis. The in vitro 24-h PD EI₅₀ values of voriconazole against C. albicans were 2.5 to 5 (1.5 to 17) fAUC/MIC. However, the 72-h PD were higher at 133 (51 to 347) fAUC/MIC for EUCAST and 94 (35 to 252) fAUC/MIC for CLSI. The mean (95% confidence interval) probability of target attainment (PTA) was 100% (95 to 100%), 97% (72 to 100%), 83% (35 to 99%), and 49% (8 to 91%) for EUCAST and 100% (97 to 100%), 99% (85 to 100%), 91% (52 to 100%), and 68% (17 to 96%) for CLSI for MICs of 0.03, 0.06, 0.125, and 0.25 mg/liter, respectively. Significantly, >95% PTA values were found for EUCAST/CLSI MICs of ≤0.03 mg/liter. For MICs of 0.06 to 0.125 mg/liter, trough levels 1 to 4 mg/liter would be required to attain the PK/PD target. A PK/PD breakpoint of C. albicans voriconazole at the ECOFF/ECV of 0.03 mg/liter was determined for both the EUCAST and CLSI methods, indicating the need for breakpoint harmonization for the reference methodologies.

Antifungal use in the surgical ICU patient

PURPOSE OF REVIEW

The successful treatment of surgical fungal infections depends of a timely and adequate source control alongside with the use of prompt systemic antifungals. The main challenge of antifungal use in critically ill surgical patients is to find a balance between rational versus indiscriminate use in order to accomplish an antifungal stewardship program.

RECENT FINDINGS

Surgical fungal infections represent an important burden in the daily clinical activity in many ICUs. The efficacy of the available antifungal drugs has not been adequately assessed in randomized controlled trials with surgical fungal infections in ICU patients. Most clinical experience is limited to case reports or uncontrolled case series. Due to the lack of adequate scientific evidence to assess the role of the different antifungals in surgical ICU patients, it is usually suggested to follow the recommendations for invasive candidiasis and candidemia.

SUMMARY

Antifungal use in the surgical patients admitted to an ICU is a complex matter and there are several elements to consider like the presence of septic shock and multiorgan failure, local epidemiology and antifungal resistance, among others. The proper use of antifungals alongside early recognition and prompt source control, are critical factors for improved outcomes.

Development and validation of a volumetric absorptive microsampling assay for analysis of voriconazole and voriconazole N-oxide in human whole blood

Voriconazole is a broad-spectrum antifungal triazole drug for the treatment of invasive fungal infections. It is extensively metabolized by hepatic drug metabolizing enzymes cytochrome (CYP) 2C19 and CYP3A4. Selective inhibition of intestinal CYP3A4 by grapefruit juice may increase the oral bioavailability of voriconazole in children. To test this hypothesis it is necessary to develop a sensitive assay for measuring voriconazole and its major metabolites in a small volume of blood. Mitra® devices from Neoteryx were employed to develop and validate the assay for the quantitation of voriconazole and voriconazole N-oxide. Mitra® devices utilize volumetric absorptive microsampling (VAMS™) technology that enables accurate and precise collection of a fixed volume (10 μL of blood), reducing or eliminating the volumetric blood hematocrit assay-bias associated with the dried blood spotting technique. We developed an ultra-performance liquid chromatographic method with tandem mass spectrometry detection for quantification of voriconazole and voriconazole N-oxide. Sample extraction of Mitra® devices, followed by reversed-phase chromatographic separation and selective detection using tandem mass spectrometry with a 4.00 minute runtime per sample was employed. Standard curves were linear between 10.0 to 10,000 ng/mL for both voriconazole and voriconazole N-oxide. Intra- and inter-day accuracy were within 87-102% and precision (CV) was <12% based on a 3-day validation study. Recoveries were ≥94 % for voriconazole and ≥87 % for voriconazole N-oxide. Voriconazole and voriconazole N-oxide were stable in human whole blood under assay conditions (19 h at room temperature and 24 h in autosampler). Voriconazole was stable for 1-month in dried microsamples under different conditions (4, -20 and -78 °C). This assay provides an efficient quantitation of voriconazole and voriconazole N-oxide and is ready to be implemented for the analysis of whole blood microsamples in a pediatric clinical trial investigating the impact of intestinal inhibition of CYP3A4 on voriconazole pharmacokinetics.

Autoinhibitory properties of the parent but not of the N-oxide metabolite contribute to infusion rate-dependent voriconazole pharmacokinetics

AIMS

The pharmacokinetics of voriconazole show a nonlinear dose-exposure relationship caused by inhibition of its own CYP3A-dependent metabolism. Because the magnitude of autoinhibition also depends on voriconazole concentrations, infusion rate might modulate voriconazole exposure. The impact of four different infusion rates on voriconazole pharmacokinetics was investigated.

METHODS

Twelve healthy participants received 100 mg voriconazole intravenous over 4 h, 400 mg over 6 h, 4 h, and 2 h in a crossover design. Oral midazolam (3 μg) was given at the end of infusion. Blood and urine samples were collected up to 48 h. Voriconazole and its N-oxide metabolite were quantified using high-performance liquid chromatography coupled to tandem mass spectrometry. Midazolam estimated metabolic clearance (eCLmet) was calculated using a limited sampling strategy. Voriconazole-N-oxide inhibition of cytochrome P450 (CYP) isoforms 2C19 and 3A4 were assessed with the P450-Glo luminescence assay.

RESULTS

Area under the concentration-time curve for 400 mg intravenous voriconazole was 16% (90% confidence interval: 12-20%) lower when administered over 6 h compared to 2 h infusion. Dose-corrected area under the concentration-time curve for 100 mg over 4 h was 34% lower compared to 400 mg over 4 h. Midazolam eCLmet was 516 ml min^-1 (420-640) following 100 mg 4 h^-1 voriconazole, 152 ml min^-1 (139-166) for 400 mg 6 h^-1 , 192 ml min^-1 (167-220) for 400 mg 4 h^-1 , and 202 ml min^-1 (189-217) for 400 mg 2 h^-1 . Concentration giving 50% CYP inhibition of voriconazole N-oxide was 146 ± 23 μmol l^-1 for CYP3A4, and 40.2 ± 4.2 μmol l^-1 for CYP2C19.

CONCLUSIONS

Voriconazole pharmacokinetics is modulated by infusion rate, an autoinhibitory contribution voriconazole metabolism by CYP3A and 2C19 and to a lesser extent its main N-oxide metabolite for CYP2C19. To avoid reduced exposure, the infusion rate should be 2 h.

Longitudinal Analysis of the Effect of Inflammation on Voriconazole Trough Concentrations

Voriconazole (VCZ) exhibits great inter- and intrapatient variability. The latter variation cannot exclusively be explained by concomitant medications, liver disease or dysfunction, and genetic polymorphisms in cytochrome P450 2C19 (CYP2C19). We hypothesized that inflammatory response in patients under VCZ medication might also influence this fluctuation in concentrations. In this study, we explored the association between inflammation, reflected by the C-reactive protein (CRP) concentration, and VCZ trough concentrations over time. A retrospective analysis of data was performed for patients with more than one steady-state VCZ trough concentration and a CRP concentration measured on the same day. A longitudinal analysis was used for series of observations obtained from many study participants over time. The approach involved inclusion of random effects and autocorrelation in linear models to reflect within-person cross-time correlation. A total of 50 patients were eligible for the study, resulting in 139 observations (paired VCZ and CRP concentrations) for the analysis, ranging from 2 to 6 observations per study participant. Inflammation, marked by the CRP concentration, had a significant association with VCZ trough concentrations (P < 0.001). Covariates such as age and interacting comedication ([es]omeprazole), also showed a significant correlation between VCZ and CRP concentrations (P < 0.05). The intrapatient variation of trough concentrations of VCZ was 1.401 (confidence interval [CI], 0.881 to 2.567), and the interpatient variation was 1.756 (CI, 0.934 to 4.440). The autocorrelation between VCZ trough concentrations at two sequential time points was calculated at 0.71 (CI, 0.51 to 0.92). The inflammatory response appears to play a significant role in the largely unpredictable pharmacokinetics of VCZ, especially in patients with high inflammatory response, as reflected by high CRP concentrations.

Clinical Practice Guideline for the Management of Candidiasis: 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.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Treatment with intrastromal and intracameral voriconazole in 2 eyes with Lasiodiplodia theobromae keratitis: case reports

To report the clinical presentation and the role of intrastromal and intracameral voriconazole injection in the management of rare cases of fungal keratitis caused by Lasiodiplodia theobromae.Two eyes of 2 patients with Lasiodiplodia keratitis unresponsive to topical and oral antifungal medications were included in this study. Diagnosis of Lasiodiplodia keratitis was confirmed by microbiological analysis, including culture-based (case 1 and 2) and DNA sequencing techniques (case 2 only).The first patient presented with multiple satellite lesions and one of these infiltrates spread deeply into the cornea, forming a stromal abscess. Another patient had a large full-thickness corneal infiltrates with several fungal balls in the anterior chamber, requiring a limbus-to-limbus therapeutic penetrating keratoplasty. Despite aggressive topical therapy, the stromal abscess continued to worsen in the first case and recurrent keratitis was observed postoperatively in the second case. Voriconazole 50 μg/0.1 mL was administered intracamerally and intrastromally around the fungal abscess as adjuncts to topical antimycotics in the first case. The second patient who needed therapeutic keratoplasty was treated with an intracameral injection of 50 μg/0.1 mL voriconazole at the end of surgery. Postoperatively, 100 μg/0.1 mL voriconazole was also injected intracamerally after the recurrence of infection was noted in the graft. Reinjections were given 48 hours apart in both cases. After the injections, all corneal and anterior chamber lesions were reduced in size and density and completely resolved within 4 weeks.Intrastromal and intracameral voriconazole injections may offer safe and effective treatment options for L theobromae keratitis.

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

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

Impact of hypoalbuminemia on voriconazole pharmacokinetics in critically ill adult patients

Setting the adequate dose for voriconazole is challenging due to its variable pharmacokinetics. We investigated the impact of hypoalbuminemia (<35 g/liter) on voriconazole pharmacokinetics in adult intensive care unit (ICU) patients treated with voriconazole (20 samples in 13 patients) as well as in plasma samples from ICU patients that had been spiked with voriconazole at concentrations of 1.5 mg/liter, 2.9 mg/liter, and 9.0 mg/liter (66 samples from 22 patients). Plasma albumin concentrations ranged from 13.8 to 38.7 g/liter. Total voriconazole concentrations in adult ICU patients treated with voriconazole ranged from 0.5 to 8.7 mg/liter. Unbound and bound voriconazole concentrations were separated using high-throughput equilibrium dialysis followed by liquid chromatography-tandem mass spectrometry (LC-MSMS). Multivariate analysis revealed a positive relationship between voriconazole plasma protein binding and plasma albumin concentrations (P < 0.001), indicating higher unbound voriconazole concentrations with decreasing albumin concentrations. The correlation is more pronounced in the presence of elevated bilirubin concentrations (P = 0.05). We therefore propose to adjust the measured total voriconazole concentrations in patients with abnormal plasma albumin and total serum bilirubin plasma concentrations who show adverse events potentially related to voriconazole via a formula that we developed. Assuming 50% protein binding on average and an upper limit of 5.5 mg/liter for total voriconazole concentrations, the upper limit for unbound voriconazole concentrations is 2.75 mg/liter. Alterations in voriconazole unbound concentrations caused by hypoalbuminemia and/or elevated bilirubin plasma concentrations cannot be countered immediately, due to the adult saturated hepatic metabolism. Consequently, increased unbound voriconazole concentrations can possibly cause adverse events, even when total voriconazole concentrations are within the reference range.

Inflammation is associated with voriconazole trough concentrations

Voriconazole concentrations display a large variability, which cannot completely be explained by known factors. Inflammation may be a contributing factor, as inflammatory stimuli can change the activities and expression levels of cytochrome P450 isoenzymes. We explored the correlation between inflammation, reflected by C-reactive protein (CRP) concentrations, and voriconazole trough concentrations. A retrospective chart review of patients with at least one steady-state voriconazole trough concentration and a CRP concentration measured on the same day was performed. A total of 128 patients were included. A significantly (P < 0.001) higher voriconazole trough concentration was observed in patients with severe inflammation (6.2 mg/liter; interquartile range [IQR], 3.4 to 8.7 mg/liter; n = 20) than in patients with moderate inflammation (3.4 mg/liter; IQR, 1.6 to 5.4 mg/liter; n = 60) and in patients with no to mild inflammation (1.6 mg/liter; IQR, 0.8 to 3.0 mg/liter; n = 48). The patients in all three groups received similar voriconazole doses based on mg/kg body weight (P = 0.368). Linear regression analyses, both unadjusted and adjusted for covariates of gender, age, dose, route of administration, liver enzymes, and interacting coadministered medications, showed a significant association between voriconazole and CRP concentration (P < 0.001). For every 1-mg/liter increase in the CRP concentration, the voriconazole trough concentration increased by 0.015 mg/liter (unadjusted 95% confidence interval [CI], 0.011 to 0.020 mg/liter; adjusted 95% CI, 0.011 to 0.019 mg/liter). Inflammation, reflected by the C-reactive protein concentration, is associated with voriconazole trough concentrations. Further research is necessary to assess if taking the inflammatory status of a patient into account is helpful in therapeutic drug monitoring of voriconazole to maintain concentrations in the therapeutic window, thereby possibly preventing suboptimal treatment or adverse events.

Tissue penetration of antifungal agents

Understanding the tissue penetration of systemically administered antifungal agents is critical for a proper appreciation of their antifungal efficacy in animals and humans. Both the time course of an antifungal drug and its absolute concentrations within tissues may differ significantly from those observed in the bloodstream. In addition, tissue concentrations must also be interpreted within the context of the pathogenesis of the various invasive fungal infections, which differ significantly. There are major technical obstacles to the estimation of concentrations of antifungal agents in various tissue subcompartments, yet these agents, even those within the same class, may exhibit markedly different tissue distributions. This review explores these issues and provides a summary of tissue concentrations of 11 currently licensed systemic antifungal agents. It also explores the therapeutic implications of their distribution at various sites of infection.

Preventing invasive fungal disease in patients with haematological malignancies and the recipients of haematopoietic stem cell transplantation: practical aspects

Invasive fungal disease (IFD), predominantly aspergillosis, is associated with significant morbidity and mortality in immunocompromised patients, especially those with haematological malignancies and recipients of allogeneic haematopoietic stem cell transplantation. There has been a great deal of scientific debate as to the effectiveness of antifungal prophylaxis in preventing infection in different patient groups and in which patients it is an appropriate management option. Deciding on an appropriate prophylaxis regimen for IFD is challenging as the incidence varies among different patient groups, due to the varied nature of their underlying haematological disease, and in different regions and centres. Attempts have been made to define risk factors and include them in treatment protocols. Impaired immune status of the patient, especially neutropenia, is a key risk factor for IFD and can sometimes be related to specific polymorphisms of genes controlling innate immunity. Risk factors also vary according to the type of fungal pathogen. Consequently, prophylaxis needs to be tailored to individual patient groups. Furthermore, the choice of antifungal agent for prophylaxis depends on the potential for drug-drug interactions with the patients' concomitant medications. Additional challenges are optimal timing of antifungal prophylaxis, when to change from prophylaxis to antifungal treatment and how to prevent recurrence of IFD. This article considers the use of antifungal prophylaxis for patients at risk of IFD in daily clinical practice, with clinical profiles that may be distinct from those covered by guidelines, and aims to provide practical advice for treatment of these patient groups.

Investigation of the Potential Relationships Between Plasma Voriconazole Concentrations and Visual Adverse Events or Liver Function Test Abnormalities

This study investigated the relationship between plasma voriconazole concentrations (pVC) and risk of visual adverse events (VAEs) or liver function test (LFT) abnormalities using longitudinal logistic regression. Seven-day mean pVC were calculated from 2,925 plasma samples (1,053 patients); in each 7-day period, the presence or absence of VAEs/abnormal LFTs was analyzed as a binary outcome variable. There was a relationship between pVC and risk of VAE (P = .011) and a weaker, but statistically significant, association with risk of aspartate transaminase (AST), alkaline phosphatase (ALP), or bilirubin but not alanine transaminase (ALT) abnormalities. The odds ratios of LFT abnormalities per 1 mug/mL pVC increase ranged from 1.07 to 1.17. Maximum weekly occurrences were 10%, 8%, 5%, and 14% for AST, ALT, ALP, and bilirubin abnormalities, respectively. Receiver-operating characteristic curve analysis indicates that individual pVC cannot be used to predict subsequent LFT abnormalities.

Safety and Pharmacokinetics of Coadministered Voriconazole and Anidulafungin

There is considerable interest in combining echinocandin and triazole antifungal agents for treatment of invasive fungal infections; however, information is needed regarding the tolerability and potential for pharmacokinetic interactions. Anidulafungin is a semisynthetic echinocandin, and voriconazole is an extended-spectrum triazole. In a random sequence, 17 subjects received anidulafungin with placebo, voriconazole with placebo, and anidulafungin with voriconazole. Anidulafungin was administered intravenously: 200 mg on day 1, then 100 mg/d on days 2 through 4. Voriconazole was administered orally: 400 mg every 12 hours on day 1, then 200 mg every 12 hours on days 2 to 4. No dose-limiting toxicities or serious adverse events occurred, and all adverse events were mild and consistent with the known safety profiles of both drugs. Pharmacokinetic parameters were not affected by coadministration. The geometric mean ratio (90% confidence interval) of the combination/drug alone for AUC(SS) was 97.4% (94.9-99.9), 97.4% (92.1-103.0), and 94.4% (87.0-102.5) for anidulafungin, voriconazole, and the voriconazole metabolite, respectively.

In vitro pharmacokinetic/pharmacodynamic modeling of voriconazole activity against Aspergillus species in a new in vitro dynamic model

The pharmacodynamics (PD) of voriconazole activity against Aspergillus spp. were studied using a new in vitro dynamic model simulating voriconazole human pharmacokinetics (PK), and the PK-PD data were bridged with human drug exposure to assess the percent target (near-maximum activity) attainment of different voriconazole dosages. Three Aspergillus clinical isolates (1 A. fumigatus, 1 A. flavus, and 1 A. terreus isolate) with CLSI MICs of 0.5 mg/liter were tested in an in vitro model simulating voriconazole PK in human plasma with C(max) values of 7, 3.5, and 1.75 mg/liter and a t(1/2) of 6 h. The area under the galactomannan index-time curve (AUC(GI)) was used as the PD parameter. In vitro PK-PD data were bridged with population human PK of voriconazole exposure, and the percent target attainment was calculated. The in vitro PK-PD relationship of fAUC(0-24)-AUC(GI) followed a sigmoid pattern (global R(2) = 0.97), with near-maximum activities (10% fungal growth) observed at an fAUC(0-24) (95% confidence interval [CI]) of 18.9 (14.4 to 23.1) mg · h/liter against A. fumigatus, 26.6 (21.1 to 32.9) mg · h/liter against A. flavus, and 36.2 (27.8 to 45.7) mg · h/liter against A. terreus (F test; P < 0.0001). Target attainment for 3, 4, and 5 mg/kg-of-body-weight voriconazole dosages was 24% (11 to 45%), 80% (32 to 97%), and 93% (86 to 97%) for A. fumigatus, 12% (5 to 26%), 63% (17 to 93%), and 86% (73 to 94%) for A. flavus, and 4% (2 to 11%), 36% (6 to 83%), and 68% (47 to 83%) for A. terreus. Based on the in vitro exposure-effect relationships, a standard dosage of voriconazole may be adequate for most patients with A. fumigatus but not A. flavus and A. terreus infections, for which a higher drug exposure may be required. This could be achieved using a higher voriconazole dosage, thus highlighting the usefulness of therapeutic drug monitoring in patients receiving a standard dosage.

Therapeutic drug monitoring of voriconazole in children

Voriconazole is an extended-spectrum triazole antifungal with activity against a wide variety of pathogens, including Aspergillus, Candida, Cryptococcus neoformans, Fusarium, and Scedosporium. It exerts its antifungal activity by blocking the synthesis of fungal cell membranes and is considered the first-line treatment for invasive aspergillosis. Because the pharmacokinetics of voriconazole can demonstrate considerable variability, it has been suggested that monitoring plasma levels of voriconazole may play an important role in optimizing the efficacy and safety of the drug in complex patients like those at risk of or who have invasive aspergillosis. In this article, we review the criteria for therapeutic drug monitoring and assess the evidence for using plasma voriconazole concentrations to individualize doses in children.

The use of antifungal therapy in neonatal intensive care

Invasive fungal infections remain a significant cause of infection-related mortality and morbidity in preterm infants. Central nervous system involvement is the hallmark of neonatal candidiasis, differentiating the disease's impact on young infants from that among all other patient populations. Over the past decade, the number of antifungal agents in development has grown, but most are not labeled for use in newborns. We summarize the findings of several antifungal studies that have been completed to date, emphasizing those including infant populations. We conclude that more studies are required for antifungals to be used safely and effectively in infants.

Pharmacodynamic effects of simulated standard doses of antifungal drugs against Aspergillus species in a new in vitro pharmacokinetic/pharmacodynamic model

In conventional ΜΙC tests, fungi are exposed to constant drug concentrations, whereas in vivo, fungi are exposed to changing drug concentrations. Therefore, we developed a new in vitro pharmacokinetic/pharmacodynamic model where human plasma pharmacokinetics of standard doses of 1 mg/kg amphotericin B, 4 mg/kg voriconazole, and 1 mg/kg caspofungin were simulated and their pharmacodynamic characteristics were determined against three clinical isolates of Aspergillus fumigatus, Aspergillus flavus, and Aspergillus terreus with identical MICs (1 mg/liter for amphotericin B, 0.5 mg/liter for voriconazole) and minimum effective concentrations (0.5 mg/liter for caspofungin). This new model consists of an internal compartment (a 10-ml dialysis tube made out of a semipermeable cellulose membrane allowing the free diffusion of antifungals but not galactomannan) inoculated with Aspergillus conidia and placed inside an external compartment (a 700-ml glass beaker) whose content is diluted after the addition of antifungal drugs by a peristaltic pump at the same rate as the clearance of the antifungal drugs in human plasma. Fungal growth was assessed by galactomannan production. Despite demonstrating the same MICs, amphotericin B completely inhibited (100%) A. fumigatus but not A. flavus and A. terreus, whose growth was delayed for 7.53 and 22.8 h, respectively. Voriconazole partially inhibited A. fumigatus (49.5%) and Α. flavus (27.9%) but not Α. terreus; it delayed their growth by 3.99 h (A. fumigatus) and 5.37 h (Α. terreus). Caspofungin did not alter galactomannan production in all of the species but A. terreus. The new model simulated human pharmacokinetics of antifungal drugs and revealed important pharmacodynamic differences in their activity.

Observational study of the clinical efficacy of voriconazole and its relationship to plasma concentrations in patients

Voriconazole is approved for treating invasive fungal infections. We examined voriconazole exposure-response relationships for patients from nine published clinical trials. The relationship between the mean voriconazole plasma concentration (C(avg)) and clinical response and between the free C(avg)/MIC ratio versus the clinical response were explored using logistic regression. The impact of covariates on response was also assessed. Monte Carlo simulation was used to estimate the relationship between the trough concentration/MIC ratio and the probability of response. The covariates individually related to response were as follows: study (P < 0.001), therapy (primary/salvage, P < 0.001), primary diagnosis (P < 0.001), race (P = 0.004), baseline bilirubin (P < 0.001), baseline alkaline phosphatase (P = 0.014), and pathogen (yeast/mold, P < 0.001). The C(avg) for 72% of the patients was 0.5 to 5.0 μg/ml, with the maximum response rate (74%) at 3.0 to 4.0 μg/ml. The C(avg) showed a nonlinear relationship to response (P < 0.003), with a lower probability at the extremes. For patients with C(avg) < 0.5 μg/ml, the response rate was 57%. The lowest response rate (56%) was seen with a C(avg) ≥ 5.0 μg/ml (18% of patients) and was associated with significantly lower mold infection responses compared to yeasts (P < 0.001) but not with voriconazole toxicity. Higher free C(avg)/MIC ratios were associated with a progressively higher probability of response. Monte Carlo simulation suggested that a trough/MIC ratio of 2 to 5 is associated with a near-maximal probability of response. The probability of response is lower at the extremes of C(avg). Patients with higher free C(avg)/MIC ratios have a higher probability of clinical response. A trough/MIC ratio of 2 to 5 can be used as a target for therapeutic drug monitoring.

Therapeutic drug monitoring of voriconazole and posaconazole

Despite the availability of newer antifungal agents, invasive fungal diseases remain a leading cause of morbidity and mortality in immunocompromised patients. Voriconazole and posaconazole are two extended-spectrum triazoles indicated for treatment and prophylaxis of invasive fungal diseases. Recently, there has been increased interest in the utility of therapeutic drug monitoring to optimize safety and efficacy of antifungals in an attempt to improve patient outcomes. We reviewed the pharmacokinetic and pharmacodynamic characteristics of voriconazole and posaconazole in the context of clinical indications for therapeutic drug monitoring. In addition, the most recent evidence examining the relationship between serum concentrations of voriconazole and posaconazole and their efficacy or toxicities was evaluated. This information was then integrated to formulate recommendations for use of therapeutic drug monitoring in clinical settings.

Voriconazole-induced inhibition of the fungicidal activity of amphotericin B in Candida strains with reduced susceptibility to voriconazole: an effect not predicted by the MIC value alone

An antagonistic effect of voriconazole on the fungicidal activity of sequential doses of amphotericin B has previously been demonstrated in Candida albicans strains susceptible to voriconazole. Because treatment failure and the need to switch to other antifungals are expected to occur more often in infections that are caused by resistant strains, it was of interest to study whether the antagonistic effect was still seen in Candida strains with reduced susceptibility to voriconazole. With the hypothesis that antagonism will not occur in voriconazole-resistant strains, C. albicans strains with characterized mechanisms of resistance against voriconazole, as well as Candida glabrata and Candida krusei strains with differences in their degrees of susceptibility to voriconazole were exposed to voriconazole or amphotericin B alone, to both drugs simultaneously, or to voriconazole followed by amphotericin B in an in vitro kinetic model. Amphotericin B administered alone or simultaneously with voriconazole resulted in fungicidal activity. When amphotericin B was administered after voriconazole, its activity was reduced (median reduction, 61%; range, 9 to 94%). Levels of voriconazole-dependent inhibition of amphotericin B activity differed significantly among the strains but were not correlated with the MIC values (correlation coefficient, -0.19; P = 0.65). Inhibition was found in C. albicans strains with increases in CDR1 and CDR2 expression but not in the strain with an increase in MDR1 expression. In summary, decreased susceptibility to voriconazole does not abolish voriconazole-dependent inhibition of the fungicidal activity of amphotericin B in voriconazole-resistant Candida strains. The degree of interaction could not be predicted by the MIC value alone.

Review of the basic and clinical pharmacology of sulfobutylether-beta-cyclodextrin (SBECD)

Despite its use in commercially available drugs such as intravenous voriconazole, there is little known in the medical literature about the clinical pharmacology of the solubilizing agent, sulfobutylether-beta-cyclodextrin (SBECD). This paper summarizes all known data on SBECD pharmacokinetics and safety. In animals, volume of distribution approximates extracellular water volume and clearance is determined by the glomerular filtration rate. SBECD does not have any apparent effects on cardiovascular or respiratory systems, nor on autonomic and somatic functions in animals. In 1- and 6-month studies in rats and dogs, the most noteworthy findings were renal tubular vacuolation and foamy macrophages in the liver and lungs. Mild toxicity in the kidney and liver as a consequence of vacuolation occurred in rats at the maximum dose of 3000 mg/kg, which is approximately 50-fold greater than the SBECD dose typically administered in man. Doses up to 1500 mg/kg produced no histopathological evidence of toxicity in dog kidneys. SBECD has also been studied in healthy volunteers and subjects with renal dysfunction. Whereas plasma SBECD levels accumulate in those with renal compromise, there were no deleterious effects on renal function. Nonetheless, serum creatinine levels should be monitored in subjects with renal compromise receiving multiple doses of SBECD.

Azole antimycotics and drug interactions in the perioperative period

PURPOSE OF REVIEW

A beneficial effect of antifungal prophylaxis on the prevention of invasive fungal infections has increased the use of azole antimycotics in intensive care and during the perioperative period. At the same time more severe illnesses are treated and multiple drug therapies are employed. Thus, the potential for severe drug-drug interactions has increased. Previous studies have shown that azole antimycotics increase the risk of many clinically significant drug interactions with potentially hazardous consequences.

RECENT FINDINGS

A recent pharmacoepidemiological study has found a more than five-fold incidence ratio in the adjusted rate of sudden death from cardiac diseases among those patients who were given simultaneously inhibitors of cytochrome P450 (CYP) enzymes and their substrates. Although new triazole antifungals are well tolerated, they still cause significant inhibition of CYP enzymes.

SUMMARY

This review focuses on azole antimycotics and anesthetic drugs being used during the perioperative period and discusses the possible clinically significant drug-drug interactions. Azole antimycotics are amongst the strongest inhibitors of CYP-mediated drug metabolism. Anesthesiologists must be aware of the interaction potential of azole antimycotics to be able to adjust their perioperative strategies according to the patient's condition and concomitant medication.