title: Liquid chromatographic determination of unbound flecainide in therapeutic drug monitoring.
abstract: An assay method was developed for determining unbound flecainide in serum by reversed phase-high performance liquid chromatography (HPLC). Serum water including unbound flecainide was separated by ultrafiltration of the serum sample and subjected to C(18)-cartridge extraction followed by HPLC analysis. The recovery of flecainide from serum water was greater than 93%. The coefficient variations for intra- and inter-day assay of flecainide were smaller than 2.4 and 3.7%, respectively. We applied the method to determining unbound flecainide in serum samples collected from 20 patients receiving oral flecainide (150-300 mg/day) for tachyarrhythmia. Total and unbound concentrations for serum flecainide were 403.5+/-200.8 ng/ml and 180.2+/-95.0 ng/ml, respectively. Linear relationship was observed between total and unbound concentrations (r=0.978, P<0.0001). Percent unbound (44.3+/-5.7%) determined in the present study agreed with the reported values. The percentage unbound tended to increase in the samples with lower alpha(1)-acid glycoprotein (<60 mg/dl). The assay method can be applied to routine determination of unbound flecainide in therapeutic drug monitoring.
authors.affiliation: Faculty of Pharmaceutical Sciences, Josai University, 1-1 Keyakidai, Sakado, Saitama 350-0295, Japan.
authors.forename: Kumi
authors.initials: K
authors.lastname: Katori
authors.forename: Masato
authors.initials: M
authors.lastname: Homma
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuga
authors.forename: Iwao
authors.initials: I
authors.lastname: Yamaguchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugibayashi
authors.forename: Yukinao
authors.initials: Y
authors.lastname: Kohda
mesh_terms: D000368:Aged; D002853:Chromatography, Liquid / Q000379:methods; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D005424:Flecainide / Q000097:blood* / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011485:Protein Binding / Q000502:physiology
chemical_list: D005424:Flecainide