Beta-receptor-active agents: role of partial agonists in patients with heart failure.

Current heart failure therapy has included both stimulation and inhibition of beta-adrenergic receptors. Full beta-agonists have not been clinically effective because of side effects or loss of efficacy over the long term. Full beta-antagonists are effective in selected patients but are not tolerated in others because of cardiac depression. Partial beta-antagonists (beta-blockers with weak intrinsic sympathomimetic activity) do not possess sufficient agonist activity to counteract their own cardiac depressant action. Partial beta-agonists produce mild beta-antagonism, but not enough to offset their overall cardiac stimulating property. The partial beta-agonists have been clinically effective in some patients with heart failure and appear to be a potentially useful and unique class of agents because of their ability to modulate cardiac beta-receptors in such a way as to avoid an excessive response to endogenous or exogenous stimuli.