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Title: A comparison of the anti-arrhythmic actions of I.C.I. 50172 and (--)-propranolol and their effects on intracellular cardiac action potentials and other features of cardiac function. Author: Papp JG, Williams EM. Journal: Br J Pharmacol; 1969 Oct; 37(2):391-9. PubMed ID: 4390670. Abstract: 1. I.C.I. 50172 had marked quinidine-like effects on intracellular cardiac action potentials at concentrations above 20 mg/l. (6.61 x 10(-5)M). The rate of rise and overshoot of the action potential, conduction velocity and contractions were decreased. (-)-Propranolol had similar effects at less than 1/30 this concentration.2. I.C.I. 50172 had 1/100 the activity of (-)-propranolol as a local anaesthetic. Since this is also the ratio of their in vitro beta-receptor blocking activities, I.C.I. 50172 provides no net increase in specificity of beta-receptor blockade.3. In contrast, the in vivo activity of I.C.I. 50172 in protecting anaesthetized guinea-pigs against ouabain-induced ventricular fibrillation was 40% that of (-)-propranolol.4. Structure-activity relations of beta-receptor blocking drugs are discussed.[Abstract] [Full Text] [Related] [New Search]