Investigations to characterize a new anti-arrhythmic drug, ORG 6001 including a simple test for calcium antagonism.

1 The compound Org 6001 (3alpha-amino-2beta-hydroxy-5alpha-androstan-17-one hydrochloride) was found in recent experiments to exhibit anti-arrhythmic activity. Evidence is presented in this paper concerning its mode of action. 2 Org 6001 was 1.8 times more potent than procaine as a local anaesthetic on desheathed frog nerve. 3 Org 6001 had no effect on the resting potential of isolated cardiac muscle of rabbit, but greatly reduced the maximum rate of depolarization tion (MRD). The action potential duration TAPD) WAS MARGINALLY PROLONGED IN ATRIAL AND VENTRICULAR MUSCLE. 4 Org 6001 preferentially shortened APD in that part of the Purkinje system in which APD is normally longer than elsewhere, so that APD