title: Mexiletine has no effect on defibrillation energy requirements in dogs.
abstract: Many of the antiarrhythmic drugs produce a rise in the ventricular defibrillation threshold (DFT). Although mexiletine has also been reported as the probable cause of a significant elevation of DFT, there has been no previous study; therefore, the effect of mexiletine on DFT was investigated in the present study. The experiments were performed on ten mongrel dogs in the open-chest state using general anesthesia. Mexiletine 1, 2, 4, 6, or 8 mg/kg was administered as the loading dose, followed by the same dose/kg per hour. In these five groups, fibrillation/defibrillation (F/D) trials were performed repeatedly every 10 minutes, until 60 minutes after starting the maintenance dose. F/D trials were also performed at 30, 45, and 60 minutes after the completion of mexiletine infusion. The heart was allowed to fibrillate for a total of 30 seconds. Applying internal paddles to the heart, energies of 2, 3, 5, 7, 10, 20, and 30 J maximum were used. The minimal energy shock that caused defibrillation was defined as the DFT. The mexiletine concentration in each group changed from 0 to 6.11 micrograms/mL, DFT ranged from 2-10 J, and no statistical correlation was found between mexiletine concentration and DFT. We conclude that mexiletine does not induce an increase in DFT in dogs.
authors.affiliation: Department of Anesthesiology, University of Tsukuba, Ibaraki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sato
authors.forename: M H
authors.initials: MH
authors.lastname: Tsuji
authors.forename: H
authors.initials: H
authors.lastname: Naito
mesh_terms: D000818:Animals; D004285:Dogs; D004554:Electric Countershock; D006439:Hemodynamics / Q000187:drug effects; D008801:Mexiletine / Q000494:pharmacology*; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*
chemical_list: D008801:Mexiletine