Doki K, Homma M, Kuga K, Kawano S, Aonuma K, Yamaguchi I, Kohda Y
Department of Pharmaceutical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
J Clin Pharm Ther. 2007 Aug;32(4):409-11. doi: 10.1111/j.1365-2710.2007.00837.x.
A 72-year-old male patient with dilated cardiomyopathy was treated with oral flecainide (100 mg/day) for persistent atrial fibrillation (AF) that could not be converted to sinus rhythm by electrical cardioversion. Initiation of flecainide treatment provided sinus rhythm without prolongation of QRS and QTc, bradycardia and first-degree atrioventricular block at a serum flecainide level of 438 ng/mL. Then, he received cardiac resynchronization therapy (CRT). Dose reduction to 50 mg/day because of stabilization of heart rate after CRT produced AF at a serum flecainide level of 270 ng/mL. Electrical cardioversion did not restore the AF to a sinus or pacing rhythm. Dose escalation of flecainide (to 100 mg/day) restored the pacing rhythm at a serum flecainide level of 401 ng/mL. This case suggests that in the Japanese population, serum flecainide level should be maintained at >300 ng/mL to control AF even after effective CRT.
