The minimum requirement for adrenergic agents is a primary or secondary amine separated from a substituted benzene ring by one or two carbons. This configuration results in strong agonist activity. As the size of the substituent attached to the amine becomes greater, particularly with respect to a t-butyl group, then the molecule typically is found to have receptor affinity without intrinsic activity, and is, therefore, an antagonist.<unk> , with its 1-methyl-3-phenylpropyl substituted amine, is greater in size relative to a t-butyl group and therefore acts predominantly as an antagonist. The overall structure of<unk>  is very polar. This was created by substituting the isopropyl group in the standard beta-blocker structure with an aralkyl group, including a carboxamide group on the meta position, and by adding a hydroxyl group on the para position.<unk>  has two chiral carbons and consequently exists as four stereoisomers. Two of these isomers, the (S,S)- and (R,S)- forms are inactive. The third, the (S,R)-isomer, is a powerful α1 blocker. The fourth isomer, the (R,R)-isomer which is also known as dilevalol, is a mixed nonselective β blocker and selective α1 blocker.<unk>  is typically given as a racemic mixture to achieve both alpha and beta receptor blocking activity. Stereoisomers of<unk>  250 px(R,R)-LabetalolCAS number: 75659-07-3 250 px(S,S)-LabetalolCAS number: 83167-24-2 250 px(R,S)-LabetalolCAS number: 83167-32-2 250 px(S,R)-LabetalolCAS number: 83167-31-1<unk>  acts by blocking alpha and beta adrenergic receptors, resulting in decreased peripheral vascular resistance without significant alteration of heart rate or cardiac output. The β:α antagonism of<unk>  is approximately 3:1. It is chemically designated in International Union of Pure and Applied Chemistry (IUPAC) nomenclature as 2-hydroxy-5-1-hydroxy-2-(1-methyl-3-phenylpropyl)aminoethylbenzamide monohydrochloride.
Labetalol
Esmolol
Nadolol
Sodium nitroprusside
Nefopam
Alvimopan
Fenoldopam
Dobutamine