[Novel types of cardiotonic drugs]

Since the use of cardiac glycosides for heart failure therapy is limited by their narrow margin of safety, numerous efforts have been made to find and develop novel cardiotonic agents that are superior to the cardiotonic glycosides. Positive inotropic drugs acting on beta-adrenoceptors and inhibitors of cAMP phosphodiesterase have been extensively studied for the treatment of patients with heart failure. The main mechanism of these agents is elevation of cAMP tissue levels. Furthermore, Ca sensitizers such as sulmazol, pimobendan, MCI-154, END 53998 and DPI 201-106 are of interest, since such a mechanism of action may be beneficial for the failing heart. Recently, cardiotonic substances with a novel mechanism of action such as gingerol and xestoquinone have been isolated from natural sources. Natural products, purealin, goniodomin and okadaic acid, have proven to be valuable pharmacological tools for studies on cardiac muscle contraction.