Bioanalysis and pharmacokinetic analysis
Plasma was obtained by centrifugation at 3,000 rpm for 10 min and stored
in polypropylene tubes at -70 ºC until concentrations were determined.
Plasma concentrations of proparnolol and 4-OH-propranolol were
determined with a validated liquid chromatography-tandem mass
spectrometry (LC-MS/MS) method. The lower limit of quantification (LLOQ)
for propranolol was 0.4 ng/mL with a linear calibration range of 0.4-100
ng/mL and that for 4-OH-propranolol was 0.3 ng/mL with a linear
calibration range of 0.3-75 ng/mL. Intra- and inter-day accuracies for
propranolol were 90.5-104.0% and those for 4-OH-propranolol were
98.8-101.3%; intra- and inter-day precisions varied with <9.4
CV% for propranolol and <6.67% for 4-OH-propranolol. The
peak plasma concentration (Cmax) and time to
Cmax (i.e. Tmax) were directly obtained
from the observed values. The area under the concentration-time curve
(AUC) from time 0 to the last measurable time (AUClast)
was calculated using the trapezoidal rule. The terminal half-life and
AUC extrapolated to infinity (AUCinf) were not
determined because the pharmacokinetic blood samplings were not
conducted until sufficient time after drug administration to evaluate
elimination phase precisely. Non-compartmental analyses were performed
using PK solutions pharmacokinetic software (SummitPK.com).
Statistical analysisDemographic characteristics and pharmacokinetic parameters were compared
among the patient groups using the Kruskal-Wallis test. Post-hoc
analysis was performed if there was a significant difference in the
comparison of pharmacokinetic parameters. A multivariate regression with
stepwise backward elimination was performed to determine the best model
for predicting the Cmax or AUClast of
propranolol. The initial variables used in the multivariate regression
were age, sex, body weight, clinical laboratory test results, and H/L
ratio. IBM SPSS Statistics™ 21 (Datasolution Inc., version 21, Seoul,
Korea) was used for statistical analysis. The two-sided level of
statistical significance was set at 0.05.