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do Vale GT, Ceron CS, Gonzaga NA, Simplicio JA, Padovan JC. Three Generations of β-blockers: History, Class Differences and Clinical Applicability. Curr Hypertens Rev 2019; 15:22-31. [PMID: 30227820 DOI: 10.2174/1573402114666180918102735] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/11/2018] [Accepted: 09/11/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND Beta-adrenergic receptors are expressed in cardiomyocytes and activated by either noradrenaline released from sympathetic synapses or circulating catecholamines. Their corresponding receptors have three subtypes, namely, β1, β2 and β3, which are members of the G protein-coupled receptors (GPCRs) family. Activation of β1-adrenergic receptors causes various physiological reactions including cardiac contraction and renin secretion from juxtaglomerular cells of the kidney. Antagonists of β-adrenergic receptors, known as β-blockers, have been used effectively for over four decades and have beneficial effects in the treatment of cardiovascular diseases. There are three generations of β-blockers according to their pharmacological properties. Firstgeneration β-blockers are non-selective, blocking both β1- and β2-receptors; second-generation β- blockers are more cardioselective in that they are more selective for β1-receptors; and thirdgeneration β-blockers are highly selective drugs for β1-receptors. The latter also display vasodilator actions by blocking α1-adrenoreceptors and activating β3-adrenergic receptors. In addition, thirdgeneration β-blockers exhibit angiogenic, antioxidant, anti-proliferative, anti-hypertrophic and antiapoptotic activities among other effects that are still under investigation. CONCLUSION The objective of this review is to describe the evolution observed during the development of the three distinctive generations, thereby highlighting the advantages of third-generation β- blockers over the other two drug classes.
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Affiliation(s)
- Gabriel T do Vale
- Laboratorio de Farmacologia, Escola de Enfermagem de Ribeirao Preto, USP, Ribeirao Preto, SP, Brazil
| | - Carla S Ceron
- Laboratorio de Farmacologia, Escola de Enfermagem de Ribeirao Preto, USP, Ribeirao Preto, SP, Brazil
| | - Natália A Gonzaga
- Laboratorio de Farmacologia, Escola de Enfermagem de Ribeirao Preto, USP, Ribeirao Preto, SP, Brazil
| | - Janaina A Simplicio
- Laboratorio de Farmacologia, Escola de Enfermagem de Ribeirao Preto, USP, Ribeirao Preto, SP, Brazil
| | - Júlio C Padovan
- The Rockefeller University, Laboratory of Blood and Vascular Biology, New York, NY, United States
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Howes LG, Rowe PR, Krum H, Louis WJ. The effects of a single dose of dilevalol on [3H]-noradrenaline plasma kinetics and plasma lipoprotein cholesterol concentrations. Br J Clin Pharmacol 1990; 29:281-7. [PMID: 2310652 PMCID: PMC1380127 DOI: 10.1111/j.1365-2125.1990.tb03637.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
1. A single oral dose of dilevalol (200 mg or 400 mg) or placebo was administered to 15 normal male volunteers in a double-blind, random order crossover study. 2. Dilevalol had no significant effect on supine blood pressures or heart rates, but caused a significant fall in systolic blood pressure 1 and 30 min following standing, and attenuated the rise in diastolic blood pressure and heart rate that accompanies standing. 3. Dilevalol caused a dose dependent increase in plasma noradrenaline levels from arterialized blood which was due to an increase in noradrenaline spillover with no change in clearance. 4. Dilevalol increased plasma levels of the noradrenaline metabolite 3,4-dihydroxyphenylethylene glycol (DHPG) (which is formed in sympathetic nerves following neuronal uptake of noradrenaline), indicating that the increase in noradrenaline spillover was not due to the blockade of neuronal uptake. 5. Acute dilevalol administration had no effect on total plasma cholesterol, HDL-cholesterol or LDL-cholesterol levels.
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Affiliation(s)
- L G Howes
- Department of Clinical Pharmacology and Therapeutics, Austin Hospital, Heidelberg, Victoria, Australia
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β-Adrenergic blocking agents with α-adrenergic blocking and vasodilator activity (survey). Pharm Chem J 1986. [DOI: 10.1007/bf00757631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Doggrell SA, Hughes EW. The effects of KF-4317, a novel combined alpha- and beta 1-adrenoreceptor antagonist, on the rat isolated right ventricle and aorta. JOURNAL OF AUTONOMIC PHARMACOLOGY 1986; 6:25-32. [PMID: 2870068 DOI: 10.1111/j.1474-8673.1986.tb00627.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of KF-4317 on the accumulation of radioactivity from [3H]-noradrenaline, and on the subsequent spontaneous and noradrenergic nerve-evoked outflow of radioactivity have been investigated in the rat isolated right ventricle. In addition the effects of KF-4317 on the contractions of the electrically-driven directly muscle stimulated rat right ventricle to isoprenaline and of the rat isolated aorta to phenylephrine and 5-hydroxytryptamine are reported. KF-4317 at 1 microM had no effect on the ability of the rat right ventricle to accumulate radioactivity from [3H]-noradrenaline. The spontaneous outflow of radioactivity, following loading of the ventricle with [3H]-noradrenaline, was increased by KF-4317 at 1 microM by a cocaine-insensitive mechanism. KF-4317 at 1 microM had no effect on the noradrenergic nerve-evoked outflow or radioactivity, and therefore is not an alpha 2-adrenoreceptor antagonist, but reduced the associated contractile response probably mainly by acting as an antagonist at postjunctional beta 1-adrenoreceptors. KF-4317 caused a parallel rightward shift of the concentration-response curve of the electrically-driven directly muscle stimulated rat right ventricle to isoprenaline. However the inhibitory effect, X9.0 and X237.2 in the presence of 0.1 and 1 microM KF-4317, was not closely concentration-related. At 1 microM, KF-4317 also depressed the maximum responses to isoprenaline. This suggests that in addition to beta 1-adrenoreceptor antagonism, KF-4317 probably exerts membrane stabilizing activity. The responses of the rat isolated aorta to phenylephrine were inhibited in a non-concentration related manner by KF-4317.(ABSTRACT TRUNCATED AT 250 WORDS)
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Doggrell SA, Hughes EW. Comparison of the effects of labetalol and SCH 19927, the R1R isomer of labetalol, on the rat isolated right ventricle and aorta. JOURNAL OF AUTONOMIC PHARMACOLOGY 1985; 5:279-88. [PMID: 4093453 DOI: 10.1111/j.1474-8673.1985.tb00551.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The effects of labetalol and its R1R isomer, SCH 19927, on the accumulation of radioactivity from [3H]-noradrenaline, and on the subsequent spontaneous and nerve-evoked outflow of radioactivity have been investigated in the rat isolated right ventricle. In addition, the effect of these agents on the contractions of the electrically-driven rat right ventricle to isoprenaline and of the rat isolated aorta to phenylephrine and 5-hydroxytryptamine are reported. Labetalol and SCH 19927 (both at 10(-6)M) inhibited the accumulation of radioactivity from [3H]-noradrenaline by 26 and 37%, respectively. The spontaneous outflow of radioactivity, following loading of the ventricle with [3H]-noradrenaline, was increased by labetalol and SCH 19927 (both at 10(-6)M) by a cocaine and idazoxan-insensitive mechanism. The nerve-evoked outflow of radioactivity was increased by labetalol and SCH 19927 (both at 10(-6)M). The ability of labetalol and SCH 19927, to increase nerve-evoked outflow was maintained in the presence of cocaine (10(-5)M) or idazoxan (10(-7)M) but reversed in the presence of cocaine and idazoxan. It is suggested that labetalol and its R1R isomer act both to inhibit neuronal uptake of noradrenaline and as antagonists at prejunctional alpha 2-adrenoreceptors. Labetalol and SCH 19927 reduced the contractile responses associated with the nerve-evoked outflow of radioactivity probably mainly by acting as antagonists at postjunctional beta 1-adrenoreceptors. The contractile responses of the electrically-driven rat right ventricle to isoprenaline were inhibited by labetalol and SCH 19927. SCH 12297 (pA2 = 8.9) was 4 times more potent than labetalol (pA2 = 8.3) as a beta 1-adrenoreceptor antagonist. The ability of labetalol and SCH 19927 at greater than or equal to 10(-7)M to depress maximal responses to isoprenaline may represent membrane stabilizing activity. The contractile responses of rat aorta to phenylephrine were inhibited by labetalol and SCH 19927. Labetalol (pA2 = 7.5) was 4X more potent than SCH 19927 (pA2 = 6.9) as an alpha 1-adrenoreceptor antagonist. SCH 19927 and labetalol had no effect on contractile responses to 5-hydroxytryptamine.
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Nakagawa Y, Nakahara H, Chin WP, Imai S. Alpha-blockade and vasodilatation induced by nipradilol, arotinolol and labetalol in pithed rats. JAPANESE JOURNAL OF PHARMACOLOGY 1985; 39:481-5. [PMID: 2419612 DOI: 10.1254/jjp.39.481] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In pithed rats two recently-introduced beta-blockers, nipradilol and arotinolol, as well as labetalol shifted the pressor dose-response curve for phenylephrine to the right. Labetalol and arotinolol did not modify the pressor dose-response curve for clonidine, while nipradilol induced a definite rightward shift. These results indicate that labetalol and arotinolol are selective alpha 1-blockers, while nipradilol is a non-selective one. In addition, all the three beta-blockers produced complex changes in the blood pressure in pithed rats. A fall of the diastolic blood pressure induced by labetalol and nipradilol was preceded by a slight rise, while arotinolol produced a fall at lower doses and a rise at higher ones. The hypotension by labetalol was abolished after propranolol, while the hypertension was suppressed by prazosin, indicating that labetalol has an intrinsic beta- and alpha 1-sympathomimetic effect. The hypertension and the hypotension produced by nipradilol and arotinolol persisted even in the presence of propranolol and prazosin or propranolol and yohimbine.
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Hughes EW, Doggrell SA. The effects of amosulalol, a novel combined alpha- and beta-adrenoreceptor antagonist, on the rat isolated right ventricle and aorta. JOURNAL OF AUTONOMIC PHARMACOLOGY 1985; 5:169-76. [PMID: 2865263 DOI: 10.1111/j.1474-8673.1985.tb00117.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of amosulalol on the accumulation of radioactivity from [3H]-noradrenaline and on the subsequent spontaneous and nerve stimulation-evoked outflow of radioactivity have been investigated in the rat isolated right ventricle. In addition the effect of amosulalol on the contractions of the electrically-driven directly muscle stimulated rat right ventricle to isoprenaline and of the rat isolated aorta to phenylephrine and 5-hydroxytryptamine are reported. Amosulalol at 10(-6)M did not prevent the accumulation of radioactivity from a solution containing [3H]-noradrenaline. The spontaneous outflow of radioactivity, following loading of the ventricle with [3H]-noradrenaline, was increased by amosulalol at 10(-6)M by a cocaine- and idazoxan- insensitive mechanism. The nerve stimulation-evoked outflow of radioactivity was increased by amosulalol (10(-6)M), cocaine (10(-5)M) and idazoxan (10(-7)M). The ability of amosulalol to increase nerve-evoked outflow was maintained in the presence of cocaine but prevented by pretreatment with idazoxan. This suggests that amusulalol is an alpha 2-adrenoreceptor antagonist. The contractile response of the electrically-driven directly muscle stimulated right ventricle to isoprenaline were inhibited by amosulalol at 10(-7) and 10(-6)M with apparent pA2 values of 7.5 and 8.1, respectively. It is suggested that amosulalol at 10(-6)M may have an action additional to beta 1-adrenoreceptor antagonism on the right ventricle. The contractile responses of the rat aorta to phenylephrine were inhibited by amosulalol at 10(-7) and 10(-6)M with a pA2 of 8.6 which was independent of concentration. Amosulalol also reduced the magnitude of the maximal responses of the aorta to 5-hydroxytryptamine.
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Cooke ED, Bowcock SA, Smith AT. Cold sensitivity in essential hypertension: the effect of beta- and combined alpha- and beta-blockade. Eur J Clin Pharmacol 1985; 29:33-6. [PMID: 2865156 DOI: 10.1007/bf00547365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The presence of cold sensitivity was investigated in three groups of patients; untreated hypertensives and hypertensives treated by a beta-adrenoceptor blocker (propranolol) or by a combined alpha- and beta-adrenoceptor blocker (labetalol) at two ambient temperatures. At a comfortable ambient (24 degrees C) one-third of the untreated and those treated with beta-blockade only showed cold sensitivity as compared with 16% of patients on the combined therapy. Under conditions of mild cold stress (20 degrees C) cold sensitivity increased in frequency in all three groups, more than half of the untreated and beta-blocked patients were affected and greater than one-third of those with alpha- and beta-blockade. These findings indicate that in the general population of hypertensives treatment with beta-adrenoceptor blockade alone may have little effect on the peripheral vasculature and that a useful degree of protection may be provided by therapy which blocks both receptors.
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Abstract
Labetalol represents the culmination of an effort to enhance the antihypertensive efficacy and to improve the hemodynamic profile of beta-adrenoceptor blockers by incorporating an additional anti-hypertensive action, that is, alpha blockade, into its pharmacologic mechanism. Reviewed here are the major aspects of the animal pharmacology of labetalol. The compound blocks beta1 and beta2-adrenoceptors nonselectively. Its blockade of alpha receptors is selective and directed at the alpha1 subset. Labetalol also dilates blood vessels independently of these mechanisms. This action is mediated by activation of vascular beta2 adrenoceptors. Thus, labetalol acts as a partial agonist on vascular smooth muscle. However, it differs markedly from other beta blockers with intrinsic sympathomimetic activity in that its agonism is directed specifically at beta2 receptors. Labetalol lowers blood pressure in a variety of animal models of hypertension. Unlike pure beta blockers, the compound reduces peripheral vascular resistance. On the basis of this profile, it is proposed that labetalol lowers blood pressure in human subjects by three independent mechanisms: (1) beta blockade, (2) alpha blockade, and (3) direct vasodilatation.
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MacCarthy EP, Bloomfield SS. Labetalol: a review of its pharmacology, pharmacokinetics, clinical uses and adverse effects. Pharmacotherapy 1983; 3:193-219. [PMID: 6310529 DOI: 10.1002/j.1875-9114.1983.tb03252.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Labetalol is a combined alpha- and beta-adrenoceptor blocking agent for oral and intravenous use in the treatment of hypertension. It is a nonselective antagonist at beta-adrenoceptors and a competitive antagonist of postsynaptic alpha 1-adrenoceptors. Labetalol is more potent at beta that at alpha 1 adrenoceptors in man; the ratio of beta-alpha antagonism is 3:1 after oral and 6.9:1 after intravenous administration. Labetalol is readily absorbed in man after oral administration, but the drug, which is lipid soluble, undergoes considerable hepatic first-pass metabolism and has an absolute bioavailability of approximately 25%. There are no active metabolites, and the elimination half-life of the drug is approximately 6 hours. Unlike conventional beta-adrenoceptor blocking drugs without intrinsic sympathomimetic activity, labetalol, when given acutely, produces a decrease in peripheral vascular resistance and blood pressure with little alteration in heart rate or cardiac output. However, like conventional beta-blockers, labetalol may influence the renin-angiotensin-aldosterone system and respiratory function. Clinical studies have shown that the antihypertensive efficacy of labetalol is superior to placebo and to diuretic therapy and is at least comparable to that of conventional beta-blockers, methyldopa, clonidine and various adrenergic neuronal blockers. Labetalol administered alone or with a diuretic is often effective when other antihypertensive regimens have failed. Studies have shown that labetalol is effective in the treatment of essential hypertension, renal hypertension, pheochromocytoma, pregnancy hypertension and hypertensive emergencies. In addition, preliminary studies indicate that labetalol may be of value in the management of ischemic heart disease. The most troublesome side effect of labetalol therapy is posture-related dizziness. Other reported side effects of the drug include gastrointestinal disturbances, tiredness, headache, scalp tingling, skin rashes, urinary retention and impotence. Side effects related to the beta-adrenoceptor blocking effect of labetalol, including asthma, heart failure and Raynaud's phenomenon, have been reported in rare instances.
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Zschiedrich H, Neurohr W, Lüth JB, Philipp T, Distler A. Sympathetic nervous activity and the pressor effect of noradrenaline under chronic alpha-beta-adrenoceptor blockade with labetalol in hypertension. KLINISCHE WOCHENSCHRIFT 1983; 61:661-7. [PMID: 6310204 DOI: 10.1007/bf01487583] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In 14 patients with essential hypertension, the influence of the alpha- and beta-adrenoceptor blocking drug labetalol on blood pressure, heart rate, plasma renin, plasma noradrenaline and pressor effect of exogenous noradrenaline was investigated during long-term treatment. During the initial four weeks of treatment, labetalol at a dose of 400 mg/day showed a slight effect only on supine blood pressure, whereas upright blood pressure was already lowered effectively after the second week of treatment (p less than 0.01). An increase in the mean dose to 850 mg/day had an additional blood pressure-lowering effect (p less than 0.001), whereby a preferential decrease of the orthostatic blood pressure was no longer apparent. Further increase in the mean dose to 1,000 mg/day at the end of the 12th week did not have an additional blood pressure-lowering effect. Body weight, plasma renin and plasma noradrenaline remained unchanged on labetalol treatment in the lowest and the highest dose. There was, however, an increased pressor effect of exogenous noradrenaline, i.e. an alpha-adrenoceptor antagonistic effect of labetalol was not detectable under these conditions. The cause of the increased pressor effect was a reduced elimination of noradrenaline from plasma, which is probably the consequence of an inhibition of the uptake 1 process by labetalol. During long-term treatment with the doses administered, the blood pressure-lowering effect of labetalol appears essentially to be the expression of the beta-adrenoceptor blocking properties of the drug.
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Cohen ML, Hynes LM. Effect of labetalol and YM-09538 on neuronal uptake of (3H)norepinephrine in the rat vas deferens. CLINICAL AND EXPERIMENTAL HYPERTENSION. PART A, THEORY AND PRACTICE 1983; 5:563-75. [PMID: 6133660 DOI: 10.3109/10641968309081793] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Labetalol and YM-09538 are combined alpha and beta receptor antagonists with demonstrated antihypertensive activity. Both compounds inhibited the uptake of (3H)norepinephrine into nerves in the rat vas deferens. However, labetalol was approximately 5 fold more potent than YM-09538 as an inhibitor of neuronal uptake. Inhibition of neuronal uptake occurred at concentrations 43 and 3800 times higher than necessary for inhibition of alpha receptors by labetalol and YM-09538, respectively. Thus YM-09538 shows a greater separation between neuronal uptake blocking properties and alpha receptor blocking properties than labetalol. This separation of activities may contribute to greater antihypertensive efficacy of YM-09538 relative to labetalol.
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Takenaka T, Asano M, Berdeaux A, Giudicelli JF. Adrenoceptor blocking hemodynamic and coronary effects of YM-09538, a new combined alpha- and beta-adrenoceptor blocking drug, in anesthetized dogs. Eur J Pharmacol 1982; 85:35-50. [PMID: 6129981 DOI: 10.1016/0014-2999(82)90422-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In anesthetized dogs. YM-09538, a new sulfonamide-substituted phenylethylamine, competitively antagonised the phenylephrine-induced vasopressor response with a DR10 of 0.50 mg/kg i.v. and the isoproterenol-induced positive chronotropic response with a DR10 of 0.66 mg/kg i.v., indicating that YM-09538 blocks both alpha 1- and beta 1-adrenoceptors and almost to the same extent. YM-09538 was 4 times more potent than phentolamine in blocking alpha 1-adrenoceptors and 3 times less potent than propranolol in blocking beta 1-adrenoceptors. YM-09538 non-selectively blocked cardiac beta 1- and vascular beta 2-receptors and was devoid of intrinsic beta-sympathomimetic and local anesthetic activities. In anesthetized closed-chest dogs, YM-09538 resembled propranolol in reducing heart rate, cardiac output, max. dLVP/dt and left ventricular cardiac work but differed from propranolol in decreasing total peripheral resistance, in increasing femoral blood flow, in causing larger falls in arterial blood pressure and in decreasing pulmonary arterial pressure. In anesthetized open-chest dogs, YM-09538 reduced heart rate, myocardial contractile force and arterial blood pressure. In non-ischemic myocardium, transmural flow and coronary vascular resistance were respectively strongly increased and decreased and the endo/epi flow ratio was slightly but not significantly reduced. In ischemic myocardium, YM-09538 also increased transmural flow and since endocardial and epicardial flows were augmented to the same extent, the endo/epi flow ratio remained unchanged. All these hemodynamic and coronary effects of YM-09538 can be accounted for the drug's combined alpha- and beta-adrenoceptors blocking properties.
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Brittain RT, Drew GM, Levy GP. The alpha- and beta-adrenoceptor blocking potencies of labetalol and its individual stereoisomers in anaesthetized dogs and in isolated tissues. Br J Pharmacol 1982; 77:105-14. [PMID: 6127131 PMCID: PMC2044658 DOI: 10.1111/j.1476-5381.1982.tb09275.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
1 The antagonist potencies of labetalol and each of its four stereoisomers have been compared at alpha 1-, beta 1- and beta 2-adrenoceptors in anaesthetized dogs and in isolated tissues. 2 The RR stereoisomer is a potent, non-selective antagonist at beta-adrenoceptors but has only weak alpha 1-adrenoceptor blocking activity. 3 The SR stereoisomer was the most potent antagonist at alpha 1-adrenoceptors, and it also had similar potency as an antagonist at beta-adrenoceptors. 4 The alpha- and beta-adrenoceptor blocking profile of the RS stereoisomer is intermediate between that of the RR and SR, but the SS stereoisomer is a relatively weak antagonist at both alpha- and beta-adrenoceptors. 5 It is concluded that, although most of the alpha 1-adrenoceptor blocking activity of labetalol is attributable to the SR stereoisomer and nearly all of its beta-adrenoceptor blocking activity resides in the RR stereoisomer, each of the stereoisomers contributes to the overall pharmacological profile of labetalol.
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Clinical Pharmacology of Antihypertensive Drug Therapy. ARTERIAL HYPERTENSION 1982. [DOI: 10.1007/978-1-4612-5657-1_32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
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Deitchman D, Perhach JL, Snyder RW. Beta-adrenoceptor and cardiovascular effects of MJ 13105 (bucindolol) in anesthetized dogs and rats. Eur J Pharmacol 1980; 61:263-77. [PMID: 6102523 DOI: 10.1016/0014-2999(80)90128-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Abstract
Labetalol has a unique and profound effect on the IOP of rabbits, in contrast to pure beta-adrenergic blockers which have little or no effect in this animal. Its action cannot be satisfactorily explained by simple alpha and beta-adrenergic blocking activity. In the concentrations used, it failed to block the action of a beta-adrenergic agonist (isoproterenol), the action of an alpha-adrenegic agonist (norepinephrine), and its own hypotensive action was neither blocked nor potentiated by the alpha-adrenergic blocker phenoxybenzamine. However, the beta blocker, timolol, did reduce the action of labetalol. These observations and the reduced response to labetalol after cervical sympathectomy, suggest that labetalol's ocular hypotensive effect may occur through some mechanism other than alpha or beta blockade.
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Prichard BN, Walden RJ. Some major consequences of actions of drugs on the autonomic nervous system in man and experience of prediction from animal studies. Pharmacol Ther 1979; 5:55-9. [PMID: 227001 DOI: 10.1016/0163-7258(79)90074-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Doggrell SA, Paton DM. Release of noradrenaline by labetalol in the rat anococcygeus muscle. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1978; 305:103-8. [PMID: 732886 DOI: 10.1007/bf00508278] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The effects of labetalol on the accumulation and spontaneous release of (--)-[3H]noradrenaline, and on contractile responses to exogenously applied (--)-noradrenaline were studied in the isolated anococcygeus muscle of the rat. 1. Labetalol (3 x 10(-7)--10(-4)M) inhibited the accumulation of (--)-[3H]noradrenaline. 2. Labetalol (10(-6)--10(-4)M) and guanethidine (6 x 10(-6) M) increased the spontaneous release of [3H] following incubation of the muscle with (--)-[3H]noradrenaline. Nortriptyline (10(-6) M) had no effect on the spontaneous release of [3H], antagonised the increased release of [3H] produced by 6 x 10(-6) M guanethidine but not that observed with 10(-5) M labetalol. Labetalol (5 x 10(-6) M) markedly increased the loss of tritiated deminated metabolites with little change in the loss of (--)-[3H]noradrenaline. 3. Labetalol (10(-7)--10(-5)M), alone or in the presence of 10(-6) M nortriptyline, had no effect on contractile responses to (--)-noradrenaline. 4. Following pretreatment with 6-hydroxydopamine (10(-3)M for 3 h) to deplete endogenous noradrenaline stores, labetalol (10(-7)--10(-5) M) inhibited responses to exogenously applied (--)-noradrenaline. 5. These results suggest that, in the rat anococcygeus muscle, labetalol is a noradrenaline releasing agent and an alpha-adrenoceptor antogonist.
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Doggrell SA, Paton DM. Effect of labetalol on the accumulation and release of noradrenaline in rat ventricle. Eur J Pharmacol 1978; 51:303-7. [PMID: 710505 DOI: 10.1016/0014-2999(78)90417-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In rat ventricular tissue, labetalol inhibited the accumulation of (-)-[3H]noradrenaline and released [3H] following preloading with (-)[3H]noradrenaline. Cocaine (30 micrometer) inhibited the release observed with tyramine (5 micrometer) and beta-phenethylamine (5 micrometer) but not that observed with labetalol (5 micrometer). Reserpine pretreatment of the animals abolished the release observed with labetalol (5 and 50 micrometer). Labetalol primarily increased the loss of deaminated metabolites of noradrenaline. It is suggested that labetalol may release (-)-noradrenaline from the vesicles.
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Drew GM, Hilditch A, Levy GP. Effect of labetalol on the uptake of [3H]-(-)-noradrenaline into the isolated vas deferens of the rat. Br J Pharmacol 1978; 63:471-4. [PMID: 667491 PMCID: PMC1668086 DOI: 10.1111/j.1476-5381.1978.tb07799.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
1 The effects of the combined alpha- and beta-adrenoceptor blocking drug, labetalol, on the uptake of [3H]-(-)-noradrenaline into the isolated vas deferens of the rat have been determined and compared with those of some other alpha-adrenoceptor blocking drugs and cocaine. 2 Labetalol, like cocaine, produced a simple competitive inhibition of [3H]-(-)-noradrenaline uptake and was about 4 times less potent than cocaine. It is concluded that labetalol is a potent inhibitor of uptake1. Phentolamine and thymoxamine also inhibited [3H]-(-)-noradrenaline uptake, and were respectively 8 and 14 times less potent than cocaine. Tolazoline, piperoxan and yohimbine were inactive in concentrations up to 30 microgram/ml. 3 The uptake1 blocking action of labetalol could explain, at least in part, the previously reported difference in its ability to block noradrenaline and phenylephrine vasopressor responses in the anaesthetized dog. 4 The possibility that uptake1 inhibitory concentrations of labetalol could be present in the blood of subjects receiving normal antihypertensive doses of the drug is discussed.
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Brogden RN, Heel RC, Speight TM, Avery GS. Labetalol: a review of its pharmacology and therapeutic use in hypertension. Drugs 1978; 15:251-70. [PMID: 25757 DOI: 10.2165/00003495-197815040-00002] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Labetalol is an orally active adrenoceptor blocking drug which is a competitive antagonist at both alpha- and beta-adrenoceptor sites. Its beta-blocking effects resemble those of propranolol, but its overall haemodynamic effects are akin to those of a comination of propranolol and an alpha-adrenoceptor blocking drugs such as phenoxybenzamine. Unlike with conventional beta-adrenoceptor blocking drugs, acute administration of labetalol reduces peripheral vascular resistance and blood pressure and has little effect on cardiac output. Theoretically, labetalol has advantages over beta-adrenoceptor blocking drugs alone in the treatment of hypertension, but any real advantage, particulary in mild or moderate hypertension, has yet to be conclusively demonstrated in therapeutic trials. Labetalol may be particularly useful in some patients whose blood pressure is not adequately controlled by beta-adrenoceptor blocking drugs alone or combined with a diuretic, but possibly at the expense of a postural hypotensive effect. Postural hypotension is the most troublesome side-effect, occasionally necessitating withdrawal of therapy, but severe side-effects such as are seen with effective antihypertensive dosages of phenoxybenzamine do not occur with labetalol.
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Blakeley AG, Summers RJ. The pharmacology of labetalol, an alpha- and beta-adrenoceptor blocking agent. GENERAL PHARMACOLOGY 1978; 9:399-402. [PMID: 32121 DOI: 10.1016/0306-3623(78)90024-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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25
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Summers RJ, Tillman J. The effects of labetalol (AH 5158) on metabolism of 3H(-)-noradrenaline released from the cat spleen by nerve stimulation. Biochem Pharmacol 1977; 26:2137-43. [PMID: 588296 DOI: 10.1016/0006-2952(77)90265-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Blakeley AG, Summers RJ. The effects of labetalol (AH 5158) on adrenergic transmission in the cat spleen. Br J Pharmacol 1977; 59:643-50. [PMID: 15698 PMCID: PMC1667764 DOI: 10.1111/j.1476-5381.1977.tb07733.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
1. The competitive alpha- and beta-adrenoceptor blocking agent labetalol, in concentrations up to 10(-4) M, produced dose-dependent increases in transmitter overflow from the isolated blood perfused spleen of the cat following nerve stimulation at 10 and 30 Hz. 2. At concentrations above 10(-4) M labetol produced a pronounced decrease in transmitter overflow. 3. Labetalol (1.5 X 10(-4) M) increased the recovery of 3H label in the venous blood following the close-arterial infusion of [3H]-(-)-noradrenaline indicating that the drug inhibits uptake of the amine. 4. Both labetalol (3.8 X 10(-5) M) and piperoxan (7.4 X 10(-6) M) produced parallel shifts to the right of the dose-response curves to noradrenaline and oxymetazoline in isolated strips of cat splenic capsule. In this preparation both drugs acted as competitive postsynaptic alpha-adrenoceptor blocking agents. 5. Labetalol (3.3 X 10(-5) M) increased the transmitter overflow following stimulation of the splenic nerves with 200 impulses at 10 Hz. The overflow could be further increased by subsequent addition of piperoxan (7.2 X 10(-6 M). Piperoxan (5.7 X 10(-6) M) alone produced a marked increase in transmitter overflow which could be further increased by subsequent addition of desmethylimipramine (DMI; 3.2 X 10(-5) M). Cocaine (1.5 X 10(-5) M) or DMI (5.4 X 10(-5 M) produced a small increase in transmitter overflow which was not further increased by addition of labetalol (2.8 X 10(-5) M). 6. Labetalol produced a biphasic effect on the responses of the isolated blood perfused spleen of the cat to nerve stimulation. With low doses (up to 10(-4) M) vascular responses were potentiated and with high doses (greater than 10(-4) M) inhibited. The potentiation was related to uptake blockade and the inhibition to decreased transmitter overflow and postsynaptic alpha-adrenoceptor blockade. 7. Labetalol appears to act as a postsynaptic alpha-adrenoceptor antagonist in the isolated blood perfused spleen of the cat with little effect on presynaptic alpha-adrenoceptors. The moderate elevation of transmitter overflow by the drug is related to the inhibitory effect of the drug on neuronal uptake rather than on presynaptic alpha-adrenoceptors.
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Harichaux P, Hary L. Some complementary data on AH 5158, an inhibitor of both alpha-and beta-adrenoceptors [proceedings]. Br J Pharmacol 1976; 58:412P. [PMID: 11020 PMCID: PMC1667557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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28
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Marshall RJ, Parratt JR. The effects of dobutamine in the early stages of acute experimental myocardial infarction in the dog [proceedings]. Br J Pharmacol 1976; 58:407P-408P. [PMID: 990595 PMCID: PMC1667530 DOI: 10.1111/j.1476-5381.1976.tb07718.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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Richards DA, Tuckman J, Prichard BN. Assessment of alpha- and beta-adrenoceptor blocking actions of labetalol. Br J Clin Pharmacol 1976; 3:849-55. [PMID: 9968 PMCID: PMC1428931 DOI: 10.1111/j.1365-2125.1976.tb00637.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Isoprenaline dose-response curves plotting increases in heart rate before and after labetalol are suggestive of competitive antagonism at beta-adrenoceptor sites. Phenylephrine dose-response curves using increases in systolic pressure before and after labetalol are suggestive of competitive antagonism at alpha-adrenoceptor sites. The ratio of alpha:beta-adrenoceptor antagonism induced by labetalol is approximately 1:3. Peak pharmacological responses after a single oral dose of labetalol (400 mg) occurred between 90-120 min after administration.
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Frick MH, Pörsti P. Combined alpha- and beta-adrenoceptor blockade with labetalol in hypertension. BRITISH MEDICAL JOURNAL 1976; 1:1046-8. [PMID: 773498 PMCID: PMC1639910 DOI: 10.1136/bmj.1.6017.1046] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The antihypertensive effect of labetalol, a new alpha- and beta-adrenoceptor inhibiting agent, was studied in 20 patients in a double-blind crossover trial. A dose of 300 mg daily reduced blood pressure only moderately in the supine position, though in the sitting and standing positions the effect was more pronounced. A dose of 600 mg daily produced statistically significant and clinically relevant reductions in blood pressure in all positions studied. The effect on heart rate was small and of significance only in reducing the heart rate increment due to a change in posture. Side effects were mild: only one patient complained of postural dizziness with the higher dose. We conclude that labetalol is useful in the treatment of mild and moderately severe hypertension.
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PROCEEDINGS OF THE British Pharmacological Society. Br J Pharmacol 1976. [DOI: 10.1111/j.1476-5381.1976.tb07648.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Blakeley AG, Summers RJ. Proceedings: The effects of AH 5158 on the overflow of transmitter and the uptake of (3H)-(--)-noradrenaline in the cat spleen. Br J Pharmacol 1976; 56:364P-365P. [PMID: 4184 PMCID: PMC1666902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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