Use dependent depression of fast sodium current in heart muscle by the new antiarrhythmic substance Bonnecor (AWD 19-166, GS 015).

A new antiarrhythmic compound (Bonnecor AWD 19-166, GS 015) was studied in its effects on the fast sodium channel in two types of cardiac preparations (rabbit ventricular myocardium, frog atrial trabecules). AWD 19-166 depressed the maximum upstroke velocity of the action potentials in ventricular myocardium (50% inhibition at 5 X 10(-6) mol/l) and decreased the fast inward current in frog atrial myocardium. High frequent trains of pacing pulses produced a pacing dependent extra block of both the maximal upstroke velocity and the fast inward current. It is concluded that AWD 19-166 blocks the fast sodium channel in a use dependent manner.