Volumetric Absorptive Microsampling for the Therapeutic Drug Monitoring of Everolimus in Patients Who Have Undergone Liver Transplant.

BACKGROUND: Therapeutic drug monitoring (TDM) of everolimus is required to prevent organ rejection in patients who have undergone transplant. Volumetric absorptive microsampling (VAMS) is a minimally invasive method for accurately collecting a small amount of blood from a patient's fingers. This study aimed to assess the applicability of VAMS for TDM of everolimus. METHODS: VAMS and venous blood samples were collected from 45 liver transplant recipients who had been receiving stable everolimus doses for at least 7 days. Whole blood everolimus concentrations were measured using ultrahigh performance liquid chromatography with tandem mass spectrometry. Deming regression and Bland-Altman analysis were performed to compare everolimus concentrations measured using VAMS (C VAMS ) and venous blood samples (C IV ). The regression coefficient (r 2 ) between C VAMS and C IV was calculated using a linear regression. The effects of the hematocrit and blood sampling time on the difference between C VAMS and C IV were investigated. RESULTS: Thirty-two participants were included in the final analysis. The Deming regression line was C IV = 1.04 × C VAMS + 0.55 [95% confidence interval (CI) of slope, 0.91-1.18; 95% CI of intercept, -0.05 to 1.16]. C VAMS and C IV were strongly correlated (r 2 = 0.92), with no proportional or constant bias. The mean difference between C VAMS and C IV was -0.79 ng/mL, with the 95% limit of agreement ranging from -2.55 to 0.97 ng/mL in a Bland-Altman plot. No effect of the hematocrit or blood sampling time was observed. CONCLUSIONS: VAMS and venous blood sampling showed good agreement for the measurement of whole blood everolimus concentrations. Less invasive VAMS can substitute for more invasive venous blood sampling in the TDM of everolimus in liver transplant patients.

Pharmacokinetic properties and bioequivalence of candesartan cilexetil in Korean healthy volunteers.

Candesartan is a long-acting and selective nonpeptide AT1 subtype angiotensin II receptor antagonist. The aim of this study was to compare the pharmacokinetics and to evaluate the bioequivalence of two candesartan cilexetil 16 mg formulations. Forty healthy volunteers were randomly assigned into two groups. After a single dose of 16 mg candesartan cilexetil oral administration, blood samples were collected at specific time intervals from 0-36 h. The plasma concentrations of candesartan cilexetil were determined by LC-MS/MS. The pharmacokinetic parameters such as AUC(last), AUC(inf) and C(max) were calculated and the 90% confidence intervals of the ratio (test/reference) pharmacokinetic parameters were obtained by analysis of variance on logarithmically transformed data. The mean for AUC(last) in the reference and the test drug were 1530.1 ± 434.6 and 1315.7 ± 368.6 ng·h/mL. The mean for AUC(inf) in the reference and the test drug were 1670.0 ± 454.5 and 1441.2 ± 397.8 ng·h/mL. The mean value for C(max) in the reference and the test drug was 142.6 ± 41.0 and 134.9 ± 41.4 ng/mL. The 90% confidence intervals for the AUC(last), AUC(inf) and C(max) were in the range of log 0.81-log 0.91, log 0.81-log 0.91 and log 0.88-log1.01, respectively. No adverse events were reported by subjects or found on analysis of vital signs or laboratory tests. This single dose study found that the test and reference products met the regulatory criteria for bioequivalence in these health volunteers. Both formulations were safe and well tolerated in 16 mg of candesartan cilexetil hydrochloride.