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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(s) -
PAPP J. GY.,
WILLIAMS E. M. VAUGHAN
Publication year - 1969
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1969.tb10576.x
Subject(s) - propranolol , cardiac function curve , cardiac action potential , action (physics) , intracellular , cardiology , medicine , electrophysiology , chemistry , repolarization , physics , heart failure , biochemistry , quantum mechanics
1 . I.C.I. 50172 had marked quinidine‐like effects on intracellular cardiac action potentials at concentrations above 20 mg/l. (6·61 × 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 β‐receptor blocking activities, I.C.I. 50172 provides no net increase in specificity of β‐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 β‐receptor blocking drugs are discussed.