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Vol.44 No.1 >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10564/1846

Title: USE-DEPENDENT BLOCK AND RECOVERY OF NA⁺ CHANNELS BY CLASS IC ANTIARRHYTHMIC DRUGS (FLECAINIDE AND ETHACIZIN) IN CANINE VENTRICULAR MUSCLE
Authors: Satoh, Hiroyasu
Matsui, Kazunori
Nakatani, Toshiaki
Narushima, Itaru
Nakashima, Toshikatsu
Keywords: class Ic antiarrhythmic drugs
flecainide
ethacizin
slow kinetic
use-dependent block
Issue Date: 28-Feb-1993
Publisher: 奈良医学会
Citation: 奈良医学雑誌 Vol.44 No.1 p.5-13
Abstract: Electrophysiological effects of flecainide and ethacizin (class Ic antiarrhythmic drugs) were examined using conventional microelectrode techniques. Flecainide significantly depressed the maximum rate of depolarization (⩒max) at 3x10⁻⁶M, and depolarized the resting potential (RP) at 10⁻⁵M, in a concentration-dependent manner. Ethacizin depressed ⩒max at 10⁻⁶M, and depolarized RP at 10⁻⁵M, significantly. However, both drugs did not affect the effective refractory period (ERP) nor the action potential duration (75% repolarization, APD₇₅). Both also had no effect on the action potential amplitude (APA). On the other hand, the drugs caused a use (or rate)-dependent block of ⩒max, and their time constants of onset of inhibition (at 3 Hz) were slow ; 6.3±1.2 msec (n=10) in the presence of flecainide (10⁻⁵M), and 6.0±1.6 msec (n=6) in the presence of ethacizin (10⁻⁵M). The time constants of the recovery were also so late : 12.2±2.5 sec (n=3) for flecainide (10⁻⁵M), and 27.1±13.3 sec (n=3) for ethacizin (2x10⁻⁶M), These results indicate that both antiarrhythmic drugs, flecainide and ethacizin, have no effect on APD₇₅ and ERP, but possess the characteristics for very slow kinetics of the use-dependent block and the recovery for fast Na⁺ channels of cardiac muscles. Ethacizin produces slower kinetics for the Na⁺ channels than flecainide.
URI: http://hdl.handle.net/10564/1846
ISSN: 04695550
13450069
Appears in Collections:Vol.44 No.1

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