Article: PDF OnlyAntiarrhythmic Effects of Bupuranolol Against Canine Ventricular Arrhythmias Induced by Halothane-Adrenaline or Two-Stage Coronary LigationHashimoto, Keitaro; Tsukada, Tokumasa; Matsuda, Hiroto; Nakagawa, Yoshito; Imai, ShoichiAuthor Information Department of Pharmacology, Niigata University School of Medicine, Niigata, Japan Journal of Cardiovascular Pharmacology: March 1979 - Volume 1 - Issue 2 - p 205-218 Free Abstract Summary We compared the β-adrenoceptor blocking actions of bupuranolol and propranolol using the response to isoprenaline of the strength of contraction of the canine blood-perfused ventricular muscle, of the rate and strength of contraction of the isolated guinea pig heart and of a guinea pig tracheal ring preparation. The potency ratios of bupuranolol to propranolol were 3.6, 3.0, 3.4, and 2.4, respectively. Bupuranolol decreased the maximum dV/dt of the canine ventricular action potential and had no sympathomimetic action. Bupuranolol effectively suppressed halothane-adrenaline ventricular arrhythmias in the dog, reflecting its potency as a β-adrenoceptor antagonist. In contrast, bupuranolol did not suppress ventricular arrhythmias induced by two-stage coronary ligation in the dog. Compared to propranolol and certain other antiarrhythmic drugs, bupuranolol had weaker effects on prolonging the effective refractory period than on the maximum dV/dt of canine ventricular muscle. This suggests that lengthening of the refractory period may be important for suppressing the two-stage coronary ligation arrhythmia and that the mechanism of this arrhythmia might be reentry. © Lippincott-Raven Publishers.