Comparison of electrophysiological and mechanical effects of droxicainide and lidocaine on heart muscle isolated from rats

A new antiarrhythmic drug, droxicainide, was compared with lidocaine in order to evaluate droxicainide's effect on heart muscle. Dose-response curves for electrophysiological and mechanical effects of the two drugs on spontaneously beating atria, electrically stimulated atria and papillary muscles isolated from rats were obtained. After increasing doses of both droxicainide and lidocaine sinus node automaticity decreased, atrial and ventricular excitability and contractile force decreased and refractoriness increased. The effects of the two drugs on atrial and ventricular muscle were qualitatively and quantitatively the same, but droxicainide was less potent. The results fit well with the concept that droxicainide is a class 1 anti-arrhythmic drug.