Steady-state plasma kinetics of slow-release propafenone, its two isomers and its main metabolites.
Steady-state plasma kinetics of propafenone (CAS 54063-53-5), the S- and R-enantiomers, and the two main metabolites were investigated in a double-blind, placebo-controlled dose-finding study using a slow-release formulation of propafenone at three different dose regimens (2 x 225 mg, 2 x 325 mg, and 2 x 425 mg). The study included a total of 24 patients (18 m, 6 f) with symptomatic ventricular arrhythmia. Since statistically valuable data was limited by a considerable portion of undetectable plasma concentrations among patients having received verum, kinetics could be followed up only in a group of 14 patients (10 m, 4 f) over a period of 12 h under steady state conditions. All patients were phenotyped prior to the study by measuring the ratio of sparteine/dehydrosparteine and three poor metabolizers were identified. A detailed description of the analytical methods used is given. With the low dose, a mean plasma level of 87 +/- 16 ng propafenone per ml plasma was obtained, with the medium dose a level of 243 +/- 34 ng/ml and with the higher dose 334 +/- 71 ng/ml were reached. All three doses of the slow-release preparation resulted in a smoothened and thus therapeutically favorable plasma concentration curve, independently from phenotype. With regard to the two propafenone enantiomers, a preferential clearance of the R-form (S/R = 2.08 +/- 0.19) could be confirmed without observing a change in the S/R ratio with time.
Volz
M
M
Max Planck Institute for Physiological and Clinical Research, Kerckhoff-Klinik GmbH, Bad Nauheim, Germany.
Mitrovic
V
V
Thiemer
J
J
Schlepper
M
M
D000107:Acetylation; D001711:Biotransformation; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007536:Isomerism; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011405:Propafenone / Q000008:administration & dosage / Q000493:pharmacokinetics*
D003692:Delayed-Action Preparations; D011405:Propafenone