Methods
Patients and Data
collection
The prospective and observational study was conducted on liver
dysfunction patients who received voriconazole between February 28, 2018
and December 11, 2018. The inclusion criteria were (1) Age≥15 years; (2)
Patients were diagnosed with liver dysfunction, such as liver failure or
liver cirrhosis according to the Child-Pugh classifications; (3)
Treatment or prevention of invasive fungal infections with voriconazole;
(4) patients contributed at least one blood sample. The exclusion
criteria were: (1) Patients who were allergic or intolerant to
voriconazole; (2) Pregnant or lactating patients; (3) Using potent
CYP450 inducer or inhibitor such as rifampicin, isoniazid, phenytoin,
carbamazepine during voriconazole treatment, but did not include proton
pump inhibitors (PPIs). (4) Patients who lacked the necessary data such
as genotype of CYP2C19, renal and liver function index. This study was
approved by Ethics Committee of The Second XiangYa Hospital of Central
South University (Changsha, China). All of the patients were provided
written informed consent before participating in the study.
Information of the following potential covariates was collected and
analyzed: age, gender (Gen), body
weight (WT), platelet counts (PLT), alanine aminotransferase (ALT),
aspartate aminotransferase (AST), total bilirubin (TBIL), direct
bilirubin (DBIL), albumin (ALB), creatinine clearance rate (CLcr) which
is calculated using the Cockcroft and Gault equation [19],
international normalized ratio (INR), CYP2C19 genotype and concomitant
medication (PPIs). Liver dysfunction was classified using Child-Pugh
scores [20], and Model for End-stage Liver Disease (MELD) scores.
The MELD score according to the following formula
[21]:\(MELD\ score=0.957\times\log_{e}\left(creatinine,mg/dl\right)+0.378\times\log_{e}\left(bilirubin,mg/dl\right)+1.12\times\log_{e}\left(\text{INR}\right)+6.43\)\(MELD\ score\ =0.957\times\log_{e}\left(creatinine,mg/dl\right)+\log_{e}(bilirubin,\ mg/dl)+1.12\times\log_{e}(INR)\ +6.43\)
Dosing regimen and Specimen
collection
Voriconazole dosing was according to the product information, where
patients with mild to moderate liver dysfunction (Child-Pugh A and B)
received standard loading doses (400 mg twice daily PO or 6 mg/kg twice
daily IV) on the first day, but half the standard maintenance dose (100
mg twice daily PO or 2 mg/kg twice daily IV). Due to the limited data on
the dosing of voriconazole in patients with severe liver dysfunction
(Child-Pugh C), dosing of these patients was based on the clinician’s
experience. The subsequent doses for
all patients were adjusted according to the measured voriconazole trough
concentration (Ctrough) and the patient’s clinical
response to voriconazole (effective or ineffective, with or without
adverse effects).
Venous blood samples (2 mL) were collected into anticoagulant tubes.
Patients were randomly collected 2-3 blood samples without intervention
in treatment at 0.5 h, 1 h, 1.5 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h after
intravenous or oral administration.
In addition, blood samples such as Ctrough from TDM were
collected from all patients after 24 hours. All voriconazole plasma
concentrations were analysed by automatic two-dimensional liquid
chromatography (2D-HPLC, Demeter Instrument Co., Ltd., Hunan, China) as
previously described [17].
DNA sequencing and CYP2C19 genetic
polymorphism
Genomic DNA was extracted using commercially available EZNA® SQ Blood
DNA Kit II. Sanger dideoxy DNA sequencing method with ABI3730xl‐full
automatic sequencing instrument (ABI Co.) from Boshang Biotechnology Co.
Ltd. (Shanghai, China) was used for CYP2C19 genotyping. CYP2C19
phenotypes were classified into five categories: ultrarapid metabolizer
(UM, CYP2C19*17/*17), rapid metabolizer (RM, CYP2C19*1/*17), extensive
metabolizer (EM, CYP2C19*1/*1), intermediate metabolizer (IM,
CYP2C19*1/*2, CYP2C19*1/*3, CYP2C19*2/*17) and poor metabolizer (PM,
CYP2C19*2/*2, CYP2C19*2/*3, CYP2C19*3/*3) [22].
Statistical analysis
The Wilcoxon two-sample test or Kruskal–Wallis test was used to compare
voriconazole Ctrough. Proportions were compared with the
Chi-square test or Fisher’s exact test. Univariate analysis was
performed to assess the association between voriconazole
Ctrough and adverse events. Receiver operating
characteristic (ROC) curves were used to explore the relationship
between voriconazole Ctrough and adverse events.
Statistical analysis was performed with SPSS version 22.0 (IBM
Corporation, Armonk, New York).
Population Pharmacokinetics
analysis
The concentration–time data of voriconazole was developed using Phoenix
NLME (version 8.0, Pharsight Corporation, USA). The first-order
conditional estimation method with the η-ε interaction option (FOCE ELS)
was used throughout the model development.
One- and two-compartment structural kinetic models with first-order and
Michaelis–Menten elimination were evaluated to describe the
pharmacokinetics of voriconazole. Finally, we comprehensively compared
the objective function value (OFV), graphical goodness of fit, the
evaluation of parameter estimates (including precision) and scientific
and physiological plausibility to choose the best base model. The oral
absorption rate constant (ka) was fixed to a value of
1.1 h−1 based on the results from a previous study
[23].
The inter-individual variability in voriconazole pharmacokinetic
parameters was described with an exponential error model. Residual error
models for voriconazole were tested as follows: the proportional error
model, the additive error model and combined error model, including
proportional plus additive error model.
Potential demographic and biochemical covariates were evaluated by
visual inspection of covariates possible relationships with
pharmacokinetic parameters included in the model. For continuous
covariates, a linear, piece-wise, exponential, and power
parameter-covariate relations were tested. Categorical covariates were
linearly included. Then, a covariate model in a stepwise
forward-inclusion and backward-elimination procedure were carried out. A
covariate was considered to be significant when inclusion of the
covariate resulted in a decrease in the objective function value (OFV)
of greater than 6.64 (p< 0.01) and elimination of the
covariate resulted in an increase in the OFV of greater than 10.83
(p< 0.001).
Goodness-of-fit (GOF) plots were used to evaluate the adequacy of
fitting. The bootstrap method was used to assess the robustness and
stability of the final model. 1000 resamples from the original data were
performed. All of the model parameters were estimated, and their median
and 2.5 and 97.5 percentiles were calculated. That was stable if the
95% CI for the parameter estimates derived from the 1000 bootstrap runs
encompassed the original final parameter estimate.
Monte Carlo simulation
1000 individuals receiving the dosing regimens including loading doses
of 200, 300 and 400 mg every 12 hours (q12h), and maintenance doses of
50, 100, 150 and 200 mg once daily (qd) or q12h orally or intravenously
were simulated by the final model. The dosing regimens were simulated
for 30-days and stratified by TBIL (TBIL-1: TBIL < 51 μmol/L;
TBIL-2: 51 μmol/L ≤ TBIL < 171 μmol/L; TBIL-3: TBIL ≥ 171
μmol/L) were performed. The voriconazole Ctrough range
of 0.5-5.0 mg/L [24] was used as the target range. The probability
of target attainment (PTA) for the Ctrough range was
examined for each of the different dosing regimens.