Towards the Elucidation of the Pharmacokinetics of Voriconazole: A Quantitative Characterization of Its Metabolism

Coadministration of Voriconazole and Rifabutin Can Increase the Risk of Adverse Drug Reactions in Patients with Multiple Infections

BACKGROUND

Coinfection of tuberculosis or nontuberculous mycobacteria and Aspergillus presents a challenge in medication selection because of the pharmacokinetic interactions between rifampin and voriconazole. Some researchers have suggested the use of rifabutin as an alternative to rifampin because of its lower hepatic cytochrome P450 enzyme induction potency despite its contraindication to drug labels. This study presents clinical cases of voriconazole and rifabutin coadministration and their potential risks.

METHODS

This retrospective study was conducted using clinical data from patients who met the following criteria: (1) admitted to Seoul National University Hospital between July 2014 and August 2023 and (2) concurrently administered rifabutin and voriconazole for more than 5 days.

RESULTS

Among the 6 patients analyzed, 4 experienced adverse drug reactions (ADRs). Three patients experienced visual and auditory hallucinations, lower extremity numbness, or delirious behavior. Two patients had prolonged the time from the start of the Q wave to the end of the T wave intervals, and 1 had elevated aspartate aminotransferase and alanine aminotransferase levels. In addition, 2 patients experienced severe nausea, poor oral intake, and weight loss. Despite receiving 1.81-fold the recommended voriconazole dosage, a therapeutic concentration (1.0-5.5 mg/L) was not achieved because of cytochrome P450 induction by rifabutin. However, during septic shock, the voriconazole concentration increased by 13.7- to 36-fold.

CONCLUSIONS

Concurrent use of rifabutin and voriconazole was associated with ADRs, including the time from the start of the Q wave to the end of the T wave prolongation, hallucinations, and severe nausea. Moreover, initially, there was a significant decrease in voriconazole concentrations; however, these concentrations substantially increased during septic shock. Therefore, it is essential to monitor drug concentrations and ADRs during concurrent use of voriconazole and rifabutin.

Electrochemical Simulation of Phase I Hepatic Metabolism of Voriconazole Using a Screen-Printed Iron(II) Phthalocyanine Electrode

Understanding the metabolism of pharmaceutical compounds is a fundamental prerequisite for ensuring their safety and efficacy in clinical use. However, conventional methods for monitoring drug metabolism often come with the drawbacks of being time-consuming and costly. In an ongoing quest for innovative approaches, the application of electrochemistry in metabolism studies has gained prominence as a promising approach for the synthesis and analysis of drug transformation products. In this study, we investigated the hepatic metabolism of voriconazole, an antifungal medication, by utilizing human liver microsomes (HLM) assay coupled with LC-MS. Based on the obtained results, the electrochemical parameters were optimized to simulate the biotransformation reactions. Among the various electrodes tested, the chemometric analysis revealed that the iron(II) phthalocyanine electrode was the most effective in catalyzing the formation of all hepatic voriconazole metabolites. These findings exemplify the potential of phthalocyanine electrodes as an efficient and cost-effective tool for simulating the intricate metabolic processes involved in drug biotransformation, offering new possibilities in the field of pharmaceutical research. Additionally, in silico analysis showed that two detected metabolites may exhibit significantly higher acute toxicity and mutagenic potential than the parent compound.

CYP3A and CYP2C19 Activity Determined by Microdosed Probe Drugs Accurately Predict Voriconazole Clearance in Healthy Adults

BACKGROUND AND OBJECTIVE

Voriconazole is an important broad-spectrum anti-fungal drug with nonlinear pharmacokinetics. The aim of this single centre fixed-sequence open-label drug-drug interaction trial in healthy participants (N = 17) was to determine whether microdosed probe drugs for CYP3A and CYP2C19 reliably predict voriconazole clearance (CLVRZ).

METHODS

At baseline, a single oral microdose of the paradigm substrates midazolam (CYP3A) and omeprazole (CYP2C19) were given to estimate their clearances (CL). Thereafter, a single oral dose of voriconazole was administered (50, 100, 200 or 400 mg), followed by the microdosed probe drugs.

RESULTS

The clearances of midazolam (CLMDZ 790-2790 mL/min at baseline; 248-1316 mL/min during voriconazole) and omeprazole (CLOMZ 66.4-2710 mL/min at baseline; 30.1-1420 mL/min during voriconazole) were highly variable. CLMDZ [geometric mean ratio (GMR) 0.586 at 50 mg voriconazole decreasing to GMR 0.196 at 400 mg voriconazole] and CLOMZ (GMR 0.590 at 50 mg decreasing to GMR 0.166 at 400 mg) were reduced with higher voriconazole doses. CLMDZ was linearly correlated with CLVRZ (slope 1.458; adjusted R2 0.528) as was CLOMZ (slope 0.807; adjusted R2 0.898). Multiple linear regression resulted in an adjusted R2 of 0.997 for the relationship CLVRZ ~ log CLOMZ + log CLMDZ using data during voriconazole treatment and an adjusted R2 of 0.997 for the relationship CLVRZ ~ log CLOMZ + log CLMDZ + voriconazole dose, using baseline data for CLMDZ and CLOMZ.

CONCLUSION

Microdosed midazolam and omeprazole accurately described and predicted total CLVRZ TRIAL REGISTRATION: EudraCT No: 2020-001017-20, registered on March 5th, 2020. DRKS: DRKS00022547, registered on August 6th, 2020.

Microdialysis of Drug and Drug Metabolite: a Comprehensive In Vitro Analysis for Voriconazole and Voriconazole N-oxide

Purpose

Voriconazole is a therapeutically challenging antifungal drug associated with high interindividual pharmacokinetic variability. As a prerequisite to performing clinical trials using the minimally-invasive sampling technique microdialysis, a comprehensive in vitro microdialysis characterization of voriconazole (VRC) and its potentially toxic N-oxide metabolite (NO) was performed.

Methods

The feasibility of simultaneous microdialysis of VRC and NO was explored in vitro by investigating the relative recovery (RR) of both compounds in the absence and presence of the other. The dependency of RR on compound combination, concentration, microdialysis catheter and study day was evaluated and quantified by linear mixed-effects modeling.

Results

Median RR of VRC and NO during individual microdialysis were high (87.6% and 91.1%). During simultaneous microdialysis of VRC and NO, median RR did not change (87.9% and 91.1%). The linear mixed-effects model confirmed the absence of significant differences between RR of VRC and NO during individual and simultaneous microdialysis as well as between the two compounds (p > 0.05). No concentration dependency of RR was found (p = 0.284). The study day was the main source of variability (46.3%) while the microdialysis catheter only had a minor effect (4.33%). VRC retrodialysis proved feasible as catheter calibration for both compounds.

Conclusion

These in vitro microdialysis results encourage the application of microdialysis in clinical trials to assess target-site concentrations of VRC and NO. This can support the generation of a coherent understanding of VRC pharmacokinetics and its sources of variability. Ultimately, a better understanding of human VRC pharmacokinetics might contribute to the development of personalized dosing strategies.

Microdialysis of Voriconazole and its N-Oxide Metabolite: Amalgamating Knowledge of Distribution and Metabolism Processes in Humans

PURPOSE

Voriconazole is an essential antifungal drug whose complex pharmacokinetics with high interindividual variability impedes effective and safe therapy. By application of the minimally-invasive sampling technique microdialysis, interstitial space fluid (ISF) concentrations of VRC and its potentially toxic N-oxide metabolite (NO) were assessed to evaluate target-site exposure for further elucidating VRC pharmacokinetics.

METHODS

Plasma and ISF samples of a clinical trial with an approved VRC dosing regimen were analyzed for VRC and NO concentrations. Concentration-time profiles, exposure assessed as area-under-the-curve (AUC) and metabolic ratios of four healthy adults in plasma and ISF were evaluated regarding the impact of multiple dosing and CYP2C19 genotype.

RESULTS

VRC and NO revealed distribution into ISF with AUC values being ≤2.82- and 17.7-fold lower compared to plasma, respectively. Intraindividual variability of metabolic ratios was largest after the first VRC dose administration while interindividual variability increased with multiple dosing. The CYP2C19 genotype influenced interindividual differences with a maximum 6- and 24-fold larger AUC_NO/AUC_VRC ratio between the intermediate and rapid metabolizer in plasma and ISF, respectively. VRC metabolism was saturated/auto-inhibited indicated by substantially decreasing metabolic concentration ratios with increasing VRC concentrations and after multiple dosing.

CONCLUSION

The feasibility of the simultaneous microdialysis of VRC and NO in vivo was demonstrated and provided new quantitative insights by leveraging distribution and metabolism processes of VRC in humans. The exploratory analysis suggested substantial dissimilarities of VRC and NO pharmacokinetics in plasma and ISF. Ultimately, a thorough understanding of target-site pharmacokinetics might contribute to the optimization of personalized VRC dosing regimens.