Local anaesthetic and antiarrhythmic properties of an aminosteroid: 3alpha-dimethyl-amino-5alpha-androstan-2beta-ol-17-one (Org. NA 13).

1. The aminosteroid Org. NA13 (3alpha-dimethylamino-5alpha-androstan-2beta-ol-17-one) was shown to be a more potent local anaesthetic than lignocaine in rats and guinea-pigs. 2. Experimental arrhythmias induced in mice by chloroform, in rats by aconitine and in dogs by coronary artery ligation were corrected by Org. NA13 at doses from 10 to 50 mg/kg intravenously. 3. In contrast to lignocaine, other local anaesthetics and beta-adrenoceptor blocking drugs, Org. NA 13 did not show any activity against the arrhythmias induced by ouabian in dogs. 4. The acute toxicity in whole animals and myocardial toxicity in the rabbit isolated atrium appeared to be less than that observed with lignocaine.