A drug used in the treatment of angina pectoris, heart failure, conduction defects, and myocardial infarction. It is a partial agonist at beta adrenergic receptors and acts as a coronary vasodilator and cardiotonic agent.

Compounds possessing both a hydroxyl (-OH) and an amino group (-NH2).

An alkaloid found in opium but not closely related to the other opium alkaloids in its structure or pharmacological actions. It is a direct-acting smooth muscle relaxant used in the treatment of impotence and as a vasodilator, especially for cerebral vasodilation. The mechanism of its pharmacological actions is not clear, but it apparently can inhibit phosphodiesterases and it may have direct actions on calcium channels.

Drugs that selectively bind to and activate beta-adrenergic receptors.