betaxolol hydrochloride

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adrenergic receptors 

Receptors which are stimulated by the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). These receptors belong to a family of G protein coupled receptors and are found in the central nervous system and many tissues innervated by the peripheral nervous system. There are two types of adrenergic receptors: (1) α-receptors, which are mainly excitatory to smooth muscles and gland cells but cause relaxation of intestinal smooth muscles; (2) β-receptors of which there are (at least) two types, β1 and β2. Generally, stimulation of β-receptors produces an inhibitory response, although in some cases the effect is excitatory (e.g. in the heart). Example: the dilator pupillae muscle contains mainly α-adrenergic receptors and stimulation (e.g. with adrenaline) produces mydriasis. On the other hand, there are drugs that block the effect of catecholamines on α- or β-adrenergic receptors and are called α- or β-blockers (or sympatholytic drugs or adrenergic receptor agonists). Example: the ciliary epithelium contains mainly β-receptors and a β-blocker such as timolol inhibits the secretion of aqueous humour, thus reducing intraocular pressure. Syn. adrenoceptor. See alpha-adrenergic agonists; alpha-adrenergic antagonists; beta-blocker; miotics; mydriatic; sympatholytic drugs; sympathomimetic drugs; autonomic nervous system.


A drug that blocks or reduces the action of neurotransmitters on beta-adrenergic receptors. It reduces secretion of aqueous humour and consequently intraocular pressure and it is used in the treatment of glaucoma. Common beta-blockers include timolol maleate, betaxolol hydrochloride, carteolol hydrochloride, levobunolol hydrochloride and metipranolol. Timolol is often used together with another agent (combination drugs), e.g. timolol and brimonidine, timolol and dorzolamide, timolol and latanoprost. Syn. beta-adrenergic antagonist; beta-adrenergic blocking agent. See adrenergic receptors; miotics; sympatholytic drugs.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann