A Beta-3 adrenergic antagonist (ò<sub>3</sub>-adrenoceptor antagonist) is an adrenergic antagonist which blocks the Beta-3 adrenergic receptors of cells, with either high specificity (an antagonist which is selective for ò<sub>3</sub> adrenoceptors) like L-748,328, L-748,337 and SR 59230A or non-specifically (an antagonist for ò<sub>3</sub> and for ò<sub>1</sub> or ò<sub>2</sub> adrenoceptors) like the non-selective betablocker Carvedilol.