Digoxin- and digitoxin-induced changes in monophasic action potential of the right ventricle of the dog heart.
The effects of digitoxin and digoxin on right ventricular monophasic action potentials were studied in intact dogs during an 8 hour observation period. Pentobarbital anaesthesia was used, and monophasic action potential recordings were obtained with the suction electrode technique. Intravenous injection of 2.0 mg digitoxin to six dogs, 2.0 mg digoxin to two dogs and 1.0 mg digoxin to five dogs caused a rapid increase in the time taken for 90% repolarisation with return to control values after 20 to 30 min. A late increase in 50 and 90% repolarisation times was observed 2 to 4 h after digitoxin, while digoxin had no such effect. The late action potential prolonging effect was inversely correlated to serum concentrations in the early elimination phase (2 to 8 h after the injection) since it reached a maximum towards the end of the observation period. Digitoxin and digoxin thus differed in their late effects on ventricular monophasic action potentials in intact dogs and may possess different antiarrhythmic activity.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004074:Digitoxin / Q000097:blood / Q000494:pharmacology*; D004077:Digoxin / Q000097:blood / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D016276:Ventricular Function
D004077:Digoxin; D004074:Digitoxin