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Adrenergic Antagonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
These are agents that act by selectively blocking β1 adrenoceptors with or without intrinsic sympathomimetic activity. The selective β1 adrenergic blockers (third generation) are betaxolol, celiprolol, nebivolol (Brunton et al., 2011; Katzung, 2009; Tripathi, 2014). Table 4.6 describes the mechanism of action, pharmacological effects, and clinical responses of selective β1 blockers (third generation).
Autonomic Responses to Microgravity and Bedrest
Published in David Robertson, Italo Biaggioni, Disorders of the Autonomic Nervous System, 2019
Victor A. Convertino, Rose Marie Robertson
If plasma noradrenaline becomes low during extended spaceflight, the attenuated hormonal stimulation might lead to increased sensitivity of adrenoreceptors such that a given adrenergic discharge such as that observed postflight would be expected to lead to excessive tachycardia. If sensitivity were relatively greater than oí2 sensitivity, a normal vasoconstrictor response to upright posture might be transformed into a more vasodepressor and tachycardic response. Especially in the setting of hypovolemia, this adrenergic discharge might be ineffective in maintaining upright blood pressure and the baroreceptor-mediated increase in heart rate might be further enhanced. While this is largely speculative, it is an intriguing possibility that could have great practical importance for the development of possible treatments not yet tested. For example, since excess tachycardia is known to be a trigger for the Bezold-Jarisch response and vasovagal syncope, the use of a β-blocker with intrinsic sympathomimetic activity might diminish β-adrenoreceptor hypersensitivity. Combined with treatment to diminish volume losses, this might improve orthostatic stability at critical times of flight and landing. Clearly, important research remains to better define the sympathetic response to spaceflight and its effects on adrenoreceptor function.
Antihypertensive Drug Classes
Published in Giuseppe Mancia, Guido Grassi, Konstantinos P. Tsioufis, Anna F. Dominiczak, Enrico Agabiti Rosei, Manual of Hypertension of the European Society of Hypertension, 2019
Engi Abdel-Hady Algharably, Reinhold Kreutz
Beta-blockers are a heterogeneous group of antihypertensive agents that antagonize the effects of catecholamines at beta-adrenoceptors (beta 1, beta 2 and beta 3) in a competitive way. Beta-blockers differ in their receptor selectivity and the presence of additional intrinsic sympathomimetic activity (ISA) (1). Beta-blockers with ISA are generally not recommended anymore. Surprisingly, the mechanisms by which beta-blockers lower BP are still not fully understood, and several modes of action are likely to be involved. A basic short-term mechanism is reducing cardiac output by their negative chronotropic and inotropic effects, which is, however, accompanied by increased peripheral resistance due to baroreceptor stimulation. Long-term lowering of BP occurs because of late lowering of peripheral vascular tone that may occur due to the resetting of baroreceptors. Other possible mechanisms include inhibition of renin secretion from the kidneys with a subsequent decrease in plasma Ang II and catecholamine levels, and a central reduction in sympathetic outflow leading to reduction in vasomotor tone. An effect on prejunctional beta receptors has also been suggested, leading to a reduction in norepinephrine release, hence adrenergic drive (2).
Efficacy of the combination of carteolol hydrochloride + latanoprost in the treatment of glaucoma and ocular hypertension
Published in Expert Opinion on Pharmacotherapy, 2018
Rebecca Russ Soares, M Reza Razeghinejad
In addition to beta-adrenergic receptor antagonism, carteolol has intrinsic sympathomimetic activity (ISA). The ISA of carteolol makes it an agonist of cardiac and vascular beta-receptors, which may lessen the risk of cardiovascular events as compared with nonselective beta-blockers [31]. This partial agonistic activity is invaluable to optic nerve ocular blood flow. A reduced ocular perfusion pressure with subsequent restriction of blood flow to the optic nerve head is theorized to contribute pathologically to glaucomatous optic neuropathy in glaucoma. This is likely secondary to a combination of high IOP and low blood flow to the optic nerve [32]. Whereas timolol and other non-selective beta-blockers are hypothesized to reduce blood flow to the optic nerve head through vascular beta2-antagonism, carteolol’s ISA may improve perfusion. The validity of this theory remains unknown, although in early studies, carteolol has been shown to enhance blood flow dynamics of the optic nerve head in animal and human models [33–35]. Timolol and other non-selective beta-blockers have had an equivocal effect on optic nerve perfusion [36–38].
Antihypertensive and cardioprotective effects of three generations of beta-adrenergic blockers: an historical perspective
Published in Hospital Practice, 2022
Steven G. Chrysant, George S. Chrysant
Intrinsic Sympathomimetic Activity (ISA): Regarding the ISA, three beta-blockers (acebutolol, labetalol, pindolol) possess this property due to partial agonism of one or more adrenergic receptors with acebutolol being cardioselective and labetalol and pindolol being nonselective [34,35]. The ISA prevents the significant decrease in heart rate (HR) and these beta-blockers are useful for the treatment of hypertensive patients with baseline slow HR. In addition, the stimulation of β2 receptors by acebutolol increases peripheral vasodilation and acebutolol has been shown to decrease mortality after myocardial infarction.
Metoprolol in the treatment of cardiovascular disease: a critical reappraisal
Published in Current Medical Research and Opinion, 2018
At present, more than 20 molecules belonging to the β-blocker class are available for clinical use. Although all these compounds share the pharmacological blockade of the adrenergic receptors, each of them is characterized by specific pharmacological properties, including selectivity of action depending on the adrenergic receptors sub-types, intrinsic sympathomimetic activity (ISA), lipid solubility, pharmacokinetic profile, and also other ancillary properties1.