Further Quinolizidine Derivatives as Antiarrhythmic Agents. 3

Fourteen quinolizidine derivatives, structurally related to the alkaloids lupinine and cytisine and previously studied for other pharmacological aims, were presently tested for antiarrhythmic, inotropic, and chronotropic effects on isolated guinea pig heart tissues, and to assess calcium antagonism in comparison to amiodarone, lidocaine, procainamide, and quinidine. All compounds, but two, compared favorably with the reference drugs. Potent antiarrhythmic activity was observed for compounds (in increasing order) 4, 1, 6 and 5. The last compound N-(3,4,5-trimethoxybenzoyl)aminohomolupinane) was outstanding, exhibiting a nanomolar potency (EC50 = 0.017 µM) for the increase of threshold of ac-arrhythmia, and being devoid of antihypertensive activity against spontaneously hypertensive rats.