This non-selective antihypertensive b-blocker (FW = 291.43 g/mol; CAS 36507-48-9; IUPAC: (S)-1-(tert-butylamino)-3-(2-cyclopentylphenoxy)- propan-2-ol), known variously as Levatol?, Levatolol?, Lobeta?, Paginol?, Hostabloc?, and Betapressin, binds to both b1- and b2-adrenergic receptors, thus exhibiting the sympathomimetic effects of a partial b-adrenergic agonist, while also acting as a serotonin (5-HT1A) receptor antagonist. By blocking b-adrenergic receptors and the sympathetic nervous system, penbutolol decreases heart rate and cardiac output, thereby lowering arterial blood pressure.