COMPARISON OF THE EFFECTS OF A BENZOTRIAZINIUM IODIDE AND QUINIDINE ON GUINEA-PIG HEART

The actions of 2‐H‐propyl‐4‐p‐tolylamino‐l,2,3‐benzotriazinium iodide (TnPBI) and quinidine were compared on guinea‐pig heart preparations. Quinidine had negative inotropic and chronotropic effects on guinea‐pig isolated atria and on Langendorff hearts: TnPBI had negative inotropic and chronotropic effects on Langendorff hearts, but showed a positive inotropic effect on isolated atria at low dose levels. Both quinidine and TnPBI increased the effective refractory period of guinea‐pig atrial preparations. The effects of TnPBI on transmembrane action potentials indicated a mixed class I and class III action according to the classification of Vaughan Williams (1970). These effects are discussed in relation to the antiarrhythmic actions of TnPBI. 1979 British Pharmacological Society