title: Timolol maleate, a new beta-adrenergic receptor blocking agent.
abstract: Some pharmacodynamic properties of an oxypropanolamine substituted novel heterocyclic compound are described. Initial studies involve comparison of the racemic mixture, dl-timolol maleate, with the beta-adrenergic receptor blocking agent propranolol in the rat, dog and cat. dl-Timolol maleate is shown to be a potent inhibitor of cardiovascular beta-adrenergic receptors activated by isoproterenol or adrenergic nerve stimulation. Blockade of alpha-adrenergic receptors is not observed even after extremely high doses. The compound is approximately 3 times more potent than propranolol in suppressing isoproterenol-induced cardioacceleration by the i.v. route of administration. dl-Timolol maleate is also extremely well absorbed when given orally, being then about 10 times more active than propranolol. Unlike propranolol, neither dl-timolol maleate nor its optical isomers possess demonstrable local anesthetic activity. Similar to propranolol and other beta-adrenergic receptor blocking agents, activity of the compound resides predominantly in the l-isomer (timolol maleate.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004285:Dogs; D006321:Heart / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D007536:Isomerism; D007545:Isoproterenol / Q000037:antagonists & inhibitors; D008297:Male; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D013830:Thiadiazoles / Q000494:pharmacology*; D014630:Vagus Nerve / Q000502:physiology
chemical_list: D000319:Adrenergic beta-Antagonists; D000779:Anesthetics, Local; D009025:Morpholines; D011412:Propanolamines; D013830:Thiadiazoles; D011433:Propranolol; D007545:Isoproterenol