Contribution of voriconazole N-oxide plasma concentration measurements to voriconazole therapeutic drug monitoring in patients with invasive fungal infection.

BACKGROUND: Voriconazole (VRC), a widely used triazole antifungal, exhibits significant inter- and intra-individual pharmacokinetic variability. The main metabolite voriconazole N-oxide (NOX) can provide information on the patient's drug metabolism capacity. OBJECTIVES: Our objectives were to implement routine measurement of NOX concentrations and to describe the metabolic ratio (MR), and the contribution of the MR to VRC therapeutic drug monitoring (TDM) by proposing a suggested dosage-adjustment algorithm. PATIENTS AND METHODS: Sixty-one patients treated with VRC were prospectively included in the study, and VRC and NOX levels were assayed by LC-MS/MS. A mixed logistic model on repeated measures was implemented to analyse risk factors for the patient's concentration to be outside the therapeutic range. RESULTS: Based on 225 measurements, the median and interquartile range were 2.4 µg/ml (1.2; 4.2), 2.1 µg/ml (1.5; 3.0) and 1.0 (0.6; 1.9) for VRC, NOX and the MR, respectively. VRC Cmin <2 µg/ml were associated with a higher MR during the previous visit. MR values >1.15 and <0.48 were determined to be the best predictors for having a VRC Cmin lower than 2 µg/ml and above 5.5 µg/ml, respectively, at the next visit. CONCLUSIONS: Measurement of NOX resulted useful for TDM of patients treated with VRC. The MR using NOX informed interpretation and clinical decision-making and is very interesting for complex patients. VRC phenotyping based on the MR is now performed routinely in our institution. A dosing algorithm has been suggested from these results.

Impact of Obesity on Voriconazole Pharmacokinetics among Pediatric Hematopoietic Cell Transplant Recipients.

Voriconazole (VCZ) is an antifungal agent with wide inter- and intrapatient pharmacokinetic (PK) variability and narrow therapeutic index. Although obesity was associated with higher VCZ trough concentrations in adults, the impact of obesity had yet to be studied in children. We characterized the PK of VCZ in obese patients by accounting for age and CYP2C19 phenotype. We conducted intensive PK studies of VCZ and VCZ N-oxide metabolite in 44 hematopoietic stem cell transplantation (HSCT) recipients aged 2 to 21 years who received prophylactic intravenous VCZ every 12 hours (q12h). Blood samples were collected at 5 and 30 minutes; at 1, 3, 6, and 9 hours after infusion completion; and immediately before the next infusion start. We estimated PK parameters with noncompartmental analysis and evaluated for an association with obesity by multiple linear regression analysis. The 44 participants included 9 (20%) with obesity. CYP2C19 metabolism phenotypes were identified as normal in 22 (50%), poor/intermediate in 13 (30%), and rapid/ultrarapid in 9 patients (21%). Obesity status significantly affects the VCZ minimum concentration of drug in serum (Cmin) (higher by 1.4 mg/liter; 95% confidence interval [CI], 0.0 to 2.8; P = 0.047) and VCZ metabolism ratio (VCZRATIO) (higher by 0.4; 95% CI, 0.0 to 0.7; P = 0.03), while no association was observed with VCZ area under the curve (AUC) (P = 0.09) after adjusting for clinical factors. A younger age and a CYP2C19 phenotype were associated with lower VCZ AUC. Obesity was associated with decreased metabolism of VCZ to its inactive N-oxide metabolite and, concurrently, increased VCZ Cmin, which is deemed clinically meaningful. Future research should aim to further characterize its effects and determine a proper dosing regimen for the obese.

Effect of CYP2C19 polymorphism on the plasma voriconazole concentration and voriconazole-to-voriconazole-N-oxide concentration ratio in elderly patients.

BACKGROUND: Effects of CYP2C19 polymorphism on voriconazole concentration (C0 ), dose-adjusted trough concentrations (C0 /dose) and voriconazole-to-voriconazole-N-oxide concentration ratio (C0 /CN ) have not been fully investigated. OBJECTIVES: To investigate correlations of CYP2C19 polymorphisms with plasma concentrations of voriconazole and the major metabolite voriconazole-N-oxide in elderly patients. METHODS: A prospective, multi-centre, non-intervention, open clinical study was conducted within Southwestern Chinese patients clinically diagnosed with invasive fungal infections, to investigate the associations of CYP2C19∗2 (681G > A), CYP2C19∗3 (636G > A) and CYP2C19∗17 (-806C > T) genetic polymorphisms with voriconazole C0 , C0 /dose and C0 /CN . RESULTS: The study included 131 adult patients, of which 72 were elderly (≥60 years) and 59 were adults (<60 years). The allele frequencies of CYP2C19∗2, ∗3 and ∗17 in the elderly cohort were 61.1%, 29.9% and 7.6%, respectively, which were similar to those in the adult cohort (66.9%, 29.7% and 2.5%, respectively; P > .05). The median voriconazole C0 (C0 ), C0 /dose and C0 /CN ratio in patients with the CYP2C19∗1/∗2 and CYP2C19∗2/∗2 genotypes were significantly higher than those in patients with the CYP2C19∗1/∗1 genotype in the adult cohort (P < .05). The C0 and C0 /dose in patients with the CYP2C19∗1/∗3 and CYP2C19∗2/∗2 genotypes, and the C0 /CN ratio for patients with the CYP2C19∗1/∗2 genotype were numerically higher than those in patients with the CYP2C19∗1/∗1 genotype in the elderly cohort, but this difference was not statistically significant (P > 0.05). The C0 , C0 /dose and C0 /CN in patients with poor metaboliser phenotypes were higher than in those with normal metaboliser phenotypes and C0 in patients with intermediate metaboliser phenotypes were significantly higher than in those with normal metaboliser phenotypes in the adult cohort (P < .05). However, there were no significant differences in the C0 , C0 /dose and C0 /CN among different CYP2C19-predicted metabolic phenotypes in the elderly cohort. CONCLUSIONS: Voriconazole C0 , C0 /dose and C0 /CN ratio are not significantly affected by the CYP2C19∗2/∗3 polymorphisms in the elderly patients.

Hypokalemia and Hyponatremia in Adult Patients Receiving Voriconazole Therapeutic Drug Monitoring.

Hypokalemia and hyponatremia are common but easily ignored adverse events in treatment with voriconazole (VCZ) that can lead to serious consequences. We intend to investigate the incidence of VCZ-induced hypokalemia and hyponatremia and their risk factors based on real-world data. A prospective study was conducted. A total of 272 patients with 414 VCZ plasma trough concentrations (C0) and VCZ N-oxide concentrations (CN) were included. The incidence of hypokalemia was 18.0% (48/266). A total of 81.2% (39/48) of patients developed hypokalemia within 14 days, whereas 56.2% (27/48) of patients developed hypokalemia within 1 week. The proportion of female patients in the hypokalemia group was higher than that in the nonhypokalemia group, as was the proportion of patients receiving intravenous VCZ. In the multivariate analysis, the independent risk factors for hypokalemia were sex, combined use of antibiotics, and VCZ CN/C0. The incidence of hyponatremia was 7.9% (21/266). The proportion of patients over 47 years of age in the hyponatremia group was 71.4% (15/21). The number of days of VCZ use in the hyponatremia group was greater than that in the nonhyponatremia group. A total of 47.6% (10/21) of patients in the hyponatremia group had supratherapeutic VCZ C0 (>5.0 µg/mL). In conclusion, hypokalemia is more likely to occur in females, in patients receiving intravenous VCZ, and in patients with the combined use of antibiotics. Hyponatremia is more likely to occur in patients older than 47 years who have been using VCZ for a long time and have higher VCZ C0 values.

The Role of Plasma Trough Concentration of Voriconazole and Voriconazole N-Oxide in Its Hepatotoxicity in Adult Patients.

Objective: Hepatotoxicity is an important cause of early withdrawal of voriconazole (VCZ). The role of the plasma trough concentration of VCZ (C0) in hepatotoxicity is confusion. VCZ N-oxide is the primary metabolite of VCZ in plasma. We investigated the role of VCZ C0 and plasma trough concentration of VCZ N-oxide (CN) in hepatotoxicity in adult patients. Materials and Methods: This was a prospective study. VCZ C0 and CN were measured using liquid chromatography-tandem mass spectrometry. Results: In total, 601 VCZ C0 and CN from 376 adult patients were included. The percentage of grade 1 or higher adverse events for ALP, ALT, AST, γ-GT, and TBIL were 35.4%, 21.0%, 30.1%, 56.2%, and 22.2%, respectively. Compared with younger adult patients, elderly patients (≥65 years) had a higher rate of grade 1 or higher adverse events of ALP. In the multivariate analysis, VCZ C0 was a risk factor for grade 1 or higher adverse events of AST in elderly patients and TBIL in younger adult patients, and VCZ CN was a risk factor for grade 1 or higher adverse events of ALT, AST, and TBIL. Results of the receiver operating characteristic curve analysis indicated that when the VCZ C0 was higher than 4.0 µg/mL, or the VCZ CN was lower than 1.7 µg/mL, the incidence of grade 1 or higher adverse events of AST and TBIL increased. Conclusion: VCZ C0 and CN were associated with liver function-related adverse events. Measurement of VCZ CN should be considered for VCZ therapeutic drug monitoring.

[The Application Study of Voriconazole and Its Metabolites Concentration Monitoring in Allogeneic Hematopoietic Stem Cell Transplantation Patients].

OBJECTIVE: To explore the application value of simultaneous monitoring of voriconazole (VRCZ) and voriconazole N-oxide (VNO) in efficacy and safety of VRCZ in the prevention and treatment of fungal infections in allogeneic hematopoietic stem cell transplantation (allo-HSCT) patients before engraftment (i.e., days +1 to +30 after transplantation). METHODS: The influencing factors of VRCZ, VNO concentration and MR (CVNO/CVRCZ) and the difference of VRCZ in the prevention and treatment of fungal infection and liver and kidney injury were analyzed. The receiver operating characteristic curve (ROC) was used to analyze the differences (the corresponding to the maximum of the Youden index on the curve was set as the cut-off value) to confirm the critical value. RESULTS: The factors affecting VRCZ concentration (CVRCZ), VNO concentration (CVNO) and MR were patient weight, VRCZ daily dose, and transplantation type (all P < 0.05). CVRCZ and CVNO in the effective group were higher than those in the ineffective group (P < 0.001), the opposite of MR (P < 0.001); the liver and renal injury group had lower MR than the normal group (P < 0.05). ROC showed that CVRCZ, C VNO and MR had important value in predicting VRCZ in the prevention and treatment of invasive fungal infections in allo-HSCT patients before engraftment, and their cutoff of concentrations were 0.95 µg/ml, 1.35 µg/ml and 1.645, respectively (AUC: 0.9677, 0.7634, 0.9564). CVRCZ and MR can assist in indicating liver ï¼»cutoff values: 0.65 µg/ml, 1.96 (AUC: 0.5971, 0.6663)ï¼½ and renal injury ï¼»cutoff values: 0.95 µg/ml, 1.705 (AUC: 0.6039, 0.6164)ï¼½. CONCLUSION: The great value of simultaneous monitoring of VRCZ, VNO and MR can predict in the efficacy and safety of VRCZ in allo-HSCT patients before engraftment. The prediction accuracy of CVRCZ was higher than that of MR, followed by that of CVNO. Increased CVRCZ and decreased MR increase the risk of liver and kidney injury.

Steady-state pharmacokinetics and metabolism of voriconazole in patients.

OBJECTIVES: Voriconazole exhibits non-linear pharmacokinetics in adults and is said to be mainly metabolized by CYP2C19 and CYP3A4 to voriconazole-N-oxide. The aim of this study was to obtain data on steady-state pharmacokinetics after dosing for at least 14 days in patients taking additional medication and in vivo data on metabolites other than voriconazole-N-oxide. PATIENTS AND METHODS: Thirty-one patients receiving voriconazole as regular therapeutic drug treatment during hospitalization participated in this prospective study. Pharmacokinetic profiles were obtained for the 12 h (dosing interval) after the first orally administered dose (400 mg) or (if possible and) after an orally administered maintenance dose (200 mg) following intake for at least 14 days (n = 14 after first dose; n = 23 after maintenance dose). Blood and urine samples were collected and the concentrations of voriconazole and three of its metabolites (the N-oxide, hydroxy-voriconazole and dihydroxy-voriconazole) were determined, as well as the CYP2C19 genotype of the patients. All other drugs taken by the participating patients were evaluated. RESULTS: A high variability of exposure (AUC) after the first dose was slightly reduced during steady-state dosing for voriconazole (82% to 71%) and the N-oxide (86% to 56%), remained high for hydroxy-voriconazole (79%) and even increased for dihydroxy-voriconazole (97% to 127%). In 16 of the 22 steady-state patients, trough plasma concentrations were <2 µg/mL. N-oxide plasma concentrations during steady state stayed almost constant. Hydroxylations of voriconazole seem to be quantitatively more important in its metabolism than N-oxidation. CONCLUSIONS: High variability in voriconazole exposure, as well as low steady-state trough plasma concentrations, suggest that the suggested steady-state dosage of 200 mg twice a day has to be increased to prevent disease progression. Therapeutic drug monitoring is probably necessary to optimize the voriconazole dose for individual patients.

Factors influencing plasma concentration of voriconazole and voriconazole- N-oxide in younger adult and elderly patients.

Background: Voriconazole (VCZ) metabolism is influenced by many factors. Identifying independent influencing factors helps optimize VCZ dosing regimens and maintain its trough concentration (C0) in the therapeutic window. Methods: We conducted a prospective study investigating independent factors influencing VCZ C0 and the VCZ C0 to VCZ N-oxide concentration ratio (C0/CN) in younger adults and elderly patients. A stepwise multivariate linear regression model, including the IL-6 inflammatory marker, was used. The receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive effect of the indicator. Results: A total of 463 VCZ C0 were analyzed from 304 patients. In younger adult patients, the independent factors that influenced VCZ C0 were the levels of total bile acid (TBA) and glutamic-pyruvic transaminase (ALT) and the use of proton-pump inhibitors. The independent factors influencing VCZ C0/CN were IL-6, age, direct bilirubin, and TBA. The TBA level was positively associated with VCZ C0 (ρ = 0.176, p = 0.019). VCZ C0 increased significantly when the TBA levels were higher than 10 µmol/L (p = 0.027). ROC curve analysis indicated that when the TBA level ≥4.05 µmol/L, the incidence of a VCZ C0 greater than 5 µg/ml (95% CI = 0.54-0.74) (p = 0.007) increased. In elderly patients, the influencing factors of VCZ C0 were DBIL, albumin, and estimated glomerular filtration rate (eGFR). The independent factors that affected VCZ C0/CN were eGFR, ALT, γ-glutamyl transferase, TBA, and platelet count. TBA levels showed a positive association with VCZ C0 (ρ = 0.204, p = 0.006) and C0/CN (ρ = 0.342, p < 0.001). VCZ C0/CN increased significantly when TBA levels were greater than 10 µmol/L (p = 0.025). ROC curve analysis indicated that when the TBA level ≥14.55 µmol/L, the incidence of a VCZ C0 greater than 5 µg/ml (95% CI = 0.52-0.71) (p = 0.048) increased. Conclusion: TBA level may serve as a novel marker for VCZ metabolism. eGFR and platelet count should also be considered when using VCZ, especially in elderly patients.

Impact of polymorphisms of pharmacokinetics-related genes and the inflammatory response on the metabolism of voriconazole.

The effects of inflammatory responses and polymorphisms of the genes encoding cytochrome P450 (CYP) (CYP2C19 and CYP3A5), flavin-containing monooxygenase 3 (FMO3), pregnane X receptor (NR1I2), constitutive androstane receptor (NR1I3), and CYP oxidoreductase (POR) on the ratio of voriconazole (VRCZ) N-oxide to VRCZ (VNO/VRCZ) and steady-state trough concentrations (C0h ) of VRCZ were investigated. A total of 56 blood samples were collected from 36 Japanese patients. Results of multiple linear regression analyses demonstrated that the presence of the extensive metabolizer CYP2C19 genotype, the dose per administration, and the presence of the NR1I2 rs3814057 C/C genotype were independent factors influencing the VNO/VRCZ ratio in patients with CRP levels of less than 40 mg/L (standardized regression coefficients (SRC) = 0.448, -0.301, and 0.390, respectively; all p < .05). With regard to the concentration of VRCZ itself, in addition to the above factors, the presence of the NR1I2 rs7643645 G/G and rs3814055 T/T genotypes were found to be independent factors influencing the VRCZ C0h in these patients (SRC = -0.430, 0.424, -0.326, 0.406 and -0.455, respectively; all p < .05). On the contrary, in patients with CRP levels of at least 40 mg/L, no independent factors were found to affect VNO/VRCZ and VRCZ C0h . Inflammatory responses, and CYP2C19 and NR1I2 polymorphisms may be useful information for the individualization of VRCZ dosages.

Inflammation Affects Liver Function and the Metabolism of Voriconazole to Voriconazole-N-Oxide in Adult and Elderly Patients.

Background: The inner association of inflammation with voriconazole (VCZ) metabolism has not been fully investigated. We intend to investigate the effects of inflammation on liver function, VCZ trough concentration (C0), C0/dose ratio and the ratio of VCZ to VCZ-N-oxide concentration (C0/CN) in adult and elderly patients. Methods: A single-center retrospective study was conducted among patients who were treated in our hospital between January 2018 and December 2021. For each eligible patient, demographic details, medical history, laboratory parameters, procalcitonin (PCT), C reactive protein (CRP), and interleukin-6 (IL-6) were collected from the medical chart. VCZ CN, TNF-α, IL-1ß, IL-8, and IL-10 concentrations were detected in blood samples. Results: A total of 356 patients were included in our study, with 195 patients in the adult cohort (<60 years) and 161 patients in the elderly cohort (≥60 years). In adult patients, CRP and IL-8 levels showed moderate association with VCZ C0/CN ratio (CRP: r = 0.512, p < 0.001; IL-8: r = 0.476, p = 0.002). IL-6 level shallowly associated with VCZ C0/CN ratio both in adult and elderly patients (r = 0.355, p = 0.003; r = 0.386, p = 0.001). A significantly higher VCZ C0, C0/dose ratio and C0/CN ratio was observed in adult patients with severe inflammation compared with patients with moderate inflammation and no to mild inflammation, as reflected by PCT levels (p < 0.05). However, there was no significant difference observed among different inflammation degrees in elderly patients. Lower albumin (AL) and higher total bilirubin (TBIL) were observed along with the degree of inflammation in both adult and elderly patients, as reflected by CRP and PCT levels (p < 0.05). Conclusion: Inflammation may affect the metabolism of VCZ to VCZ-N-oxide both in adult and elderly patients, and decreased plasma AL levels and increased TBIL levels under inflammatory conditions may also alter VCZ metabolism.

Cutaneous Squamous Cell Carcinoma Arising in Immunosuppressed Patients: A Systematic Review of Tumor Profiling Studies.

As solid organ transplantation becomes more prevalent, more individuals are living as members of the immunosuppressed population with an elevated risk for cutaneous squamous cell carcinoma (cSCC). Although great progress has been made in understanding the pathogenesis of cSCC in general, little is known about the drivers of tumorigenesis in immunosuppressed patients and organ-transplant recipients, specifically. This systematic review sought to synthesize information regarding the genetic and epigenetic alterations as well as changes in protein and mRNA expression that place this growing population at risk for cSCC, influence treatment response, and promote tumor aggressiveness. This review will provide investigators with a framework to identify future areas of investigation and clinicians with additional insight into how to best manage these patients.

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.

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.

Photosensitisation by voriconazole-N-oxide results from a sequence of solvent and pH-dependent photochemical and thermal reactions.

The phototoxicity of voriconazole (VN) prescribed in the treatment of severe fungal infections is frequently reported. Its major metabolite, a N-oxide derivative (VNO), was suspected to be the photosensitizer because it shows a maximum absorbance at ~310 nm in aqueous solutions. It was reported that the VNO photoproduct (VNOP) was phototoxic to human keratinocytes. Steady state and laser flash photolyses were performed to shed light on the phototoxic properties of VNO and VNOP. The quantum yield of the VNOP production by UVB-UVA light in buffered or alcoholic solutions is 0.6. VNOP has been identified as (2R,3S)-2-(2,4-difluorophenyl)-3-(5-fluoro-7-oxa-1,3-diazabicyclo[4.1.0]hepta-2,4-dien-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol. VNOP undergoes a marked thermal degradation and an efficient UVA photolysis with well differentiated kinetics and end-products. The temperature-dependent VNOP dark degradation produces a single product VNOPD identified as 6-[(2S,3R)-3-(2,4-difluorophenyl)-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)butan-2-yl]-5-fluoropyrimidin-4-ol with absorbance maximum at 308 nm and ε = 2700 M-1 cm-1. Under UVB-UVA irradiation, VNOPD, the stable end-product, is a remarkable photodynamic photosensitizer towards Trp and His. The Trp photo-oxidation (Φox(Trp) = 0.13) mainly involves type I radical reactions whereas His is oxidized by 1O2 (Φox(His) = 0.012). These results force us to question the validity of the in vitro photosensitization of human keratinocytes by VNO and VNOP previously reported.

The effects of cytochrome P450 2C19 polymorphism on the metabolism of voriconazole in vitro.

BACKGROUND: CYP/CYP450 2C19 (CYP2C19) is a highly polymorphic enzyme and exhibits individual differences in metabolic activity. The purpose of this research was mainly to explore the catalytic activities of 30 CYP2C19 variants on the substrate voriconazole in vitro, including 24 novel CYP2C19 variants (2C19.2E-.2H, .2J, .3C, .29-.33, L16F, 35FS, R124Q, R125G, T130M, N231T, M255T, R261W, N277K, S303N, I327T, N403I, and A430V) found in Chinese Han population for the first time. METHODS: These CYP2C19 variants were expressed in Spodoptera frugiperda (Sf) 21 insect cells using the baculovirus-mediated expression system. The substrate voriconazole was incubated with the abovementioned proteins at 37°C for 30 minutes in an appropriate designed system. Then through detecting its major metabolite voriconazole N-oxide by ultra-performance liquid chromatography tandem mass spectrometry, available data were obtained to explain the influence of CYP2C19 polymorphisms on voriconazole. RESULTS: From the results, when compared to CYP2C19.1, most variants exhibited either reduced Vmax and/or increased Km value, indicating that the intrinsic clearance (Vmax/Km ) values of most variants were significantly altered. The catalytic activities of 20 novel variants exhibited decreases in different degrees compared to CYP2C19.1, with relative clearance values ranging from 1.11% to 83.78%. However, L16F exhibited the increased catalytic activity for 135.68%. In addition, the kinetic parameters of four variants (2C19.2H, .3, 35FS, and R124Q) could not be detected, due to the defective gene. CONCLUSION: This is the first study to report the effects of CYP2C19 polymorphisms on vori-conazole metabolism in vitro, and we hope these data could lay the foundation for the early clinical research and individualized treatment.

Simultaneous quantification of systemic azoles and their major metabolites in human serum by HPLC/PDA: role of azole metabolic rate.

We describe the development and validation of a novel liquid chromatography assay (HPLC/PDA) for simultaneous quantification of voriconazole, itraconazole, and posaconazole, as well as some of their major metabolites, voriconazole N-oxide and hydroxy-itraconazole, in human serum. Analytes were detected using a PDA system that allows the characterization of the specific UV spectra of each compound. The assay exhibited linearity between 0.25-16 mg/L for all the compounds tested. The accuracy and within- and between-day precision of the assay were in acceptable ranges. We successfully quantified the azoles and some of their metabolites in a collection of clinical samples collected from treated patients. The method also allows assessing the metabolic rate of several azoles being useful to predict the metabolic profile of a particular patient and to anticipate toxicity or efficacy during the treatment.