title: Assessment of serum flecainide trough levels in patients with tachyarrhythmia.
abstract: The reported therapeutic range for trough flecainide concentration is 200-1000 ng mL(-1). Severe adverse events, such as ventricular arrhythmias, have occurred occasionally in patients whose serum flecainide exceeded 1000 ng mL(-1). However, the lower limit remains controversial. We have evaluated blood flecainide concentrations in patients with tachyarrhythmia who received the drug to control palpitation. We measured the flecainide trough levels and incidence and frequency of palpitation of 44 outpatients receiving oral flecainide (150-300 mg daily). Mean serum flecainide trough concentrations differed significantly between patients with (n = 14) and without (n = 30) palpitation (259.5 +/- 85.2 vs 462.2 +/- 197.7 ng mL(-1), P < 0.01). The frequency of palpitation decreased as the serum flecainide concentration increased. The incidence of palpitation was 65% at serum flecainide concentrations < 300 ng mL(-1) and 11% at > or = 300 ng mL(-1). QRS values were increased significantly in patients with serum flecainide < 300 ng mL(-1) compared with > or = 300 ng mL(-1) (0.110 +/- 0.016 s vs 0.093 +/- 0.019 s, P < 0.05). We concluded that to control paroxysm in patients receiving flecainide for tachyarrhythmia serum flecainide concentrations should be maintained at > or = 300 ng mL(-1).
authors.affiliation: Department of Pharmaceutical Sciences, Institute of Clinical Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ten-nodai 1-1-1, Tsukuba, Ibaraki 305-8575, Japan. masatoh@md.tsukuba.ac.jp
authors.forename: Masato
authors.initials: M
authors.lastname: Homma
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kuga
authors.forename: Kosuke
authors.initials: K
authors.lastname: Doki
authors.forename: Kumi
authors.initials: K
authors.lastname: Katori
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: D000889:Anti-Arrhythmia Agents / Q000097:blood* / Q000493:pharmacokinetics; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects; D005260:Female; D005424:Flecainide / Q000097:blood* / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D013056:Spectrophotometry, Ultraviolet; D013610:Tachycardia / Q000097:blood*
chemical_list: D000889:Anti-Arrhythmia Agents; D005424:Flecainide