ISOPROTERENOL IS A POTENT AGONIST OF BOTH BETA-1- AND BETA-2 ADRENERGIC RECEPTORS, WITH MINIMAL TO NO EFFECTS ON ALPHA-ADRENERGIC RECEPTORS AT THERAPEUTIC DOSES. ISOPROTERENOL STIMULATES BETA-RECEPTORS THROUGHOUT THE BODY EXCEPT FOR THE SWEAT GLANDS AND FACIAL ARTERIES. INTRACELLULARLY, THE ACTIONS OF ISOPROTERENOL ARE MEDIATED BY CYCLIC ADENOSINE MONOPHOSPHATE (CAMP), THE PRODUCTION OF WHICH IS AUGMENTED BY BETA STIMULATION. CONSEQUENTLY, ISOPROTERENOL STIMULATES MYOCARDIAL PERFORMANCE PRIMARILY VIA POSITIVE INOTROPIC AND CHRONOTROPIC EFFECTS, AND IMPROVES CORONARY ARTERY BLOOD FLOW, ALTHOUGH USUALLY NOT ENOUGH TO COMPLETELY MEET THE INCREASED MYOCARDIAL OXYGEN DEMAND RESULTING FROM VIGOROUS BETA STIMULATION. IN ADDITION, ISOPROTERENOL WILL RELAX BRONCHIAL, GI, AND SKELETAL SMOOTH MUSCLE, RELIEVING BRONCHOSPASM AND INCREASING BLOOD FLOW.