In vivo and in vitro electrophysiologic effects of terodiline on dog myocardium.
BACKGROUND
Terodiline hydrochloride, widely prescribed for urinary incontinence, has been reported to cause bradycardia and torsades de pointes.


RESULTS
In this study, we characterized the electrophysiologic effects of terodiline in dog cardiac tissues in vivo and in isolated canine cardiac Purkinje fibers. Terodiline (1 to 10 microM) resulted in dose-dependent reduction of action potential amplitude and maximal upstroke velocity (Vmax). The threshold for these effects was approximately 2 microM (0.6 mg/L), and the changes were cycle-length dependent. Terodiline (> or = 2 microM) also depressed the action potential plateau but did not significantly alter action potential duration at concentrations < or = 10 microM. In vivo studies demonstrated that high doses of terodiline (3 mg/kg) lengthened AH and HV intervals, slowed spontaneous sinus rate, prolonged ventricular refractoriness, and inhibited vagally induced slowing of the sinus node. Sympathetic effects on spontaneous sinus rate were unchanged. In both isolated canine Purkinje fibers and anesthetized dogs, terodiline did not evoke afterdepolarizations, repetitive firing, or ventricular tachyarrhythmias under normal or hypokalemic conditions.


CONCLUSIONS
Our findings suggest that terodiline (> or = 1 to 2 microM) leads to blockade of sodium and calcium channels as well as muscarinic receptors in canine cardiac tissues.
Pressler
M L
ML
Department of Medicine, Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis 46202-4800, USA.
Warner
M R
MR
Rubart
M
M
Rardon
D P
DP
Zipes
D P
DP
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D016275:Atrial Function / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002082:Butylamines / Q000097:blood / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004285:Dogs; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006327:Heart Block; D009994:Osmolar Concentration; D011690:Purkinje Fibers / Q000187:drug effects; D011802:Quinidine / Q000494:pharmacology; D012032:Refractory Period, Electrophysiological; D016276:Ventricular Function / Q000187:drug effects; D016277:Ventricular Function, Left
D002082:Butylamines; D002121:Calcium Channel Blockers; C010637:terodiline; D011802:Quinidine