Comparison of the beta 1 and beta 2 adrenoceptor blocking properties of acebutolol and propranolol

Selectivity of acebutolol, atenolol, and metoprolol in healthy volunteers estimated by the extent the drugs occupy beta 2-receptors in the circulating plasma

The selectivity of acebutolol, atenolol, and metoprolol in healthy volunteers was estimated by determining the extent to which the drugs occupied beta 1-receptors of rabbit lung and beta 2-receptors of rat reticulocytes in the circulating plasma after drug intake. This ex vivo method had the advantage of including all drug components contributing to the drug-receptor equilibrium in vivo and of excluding the factors regulating organ sensitivity to catecholamine stimulation. The oral doses of 400 mg acebutolol, 100 mg atenolol, and 100 mg metoprolol were administered to six healthy male volunteers using a double-blind, randomized, and cross-over study design. The three drugs occupied beta 1-receptors to a similar extent at 2 hours after drug intake. The receptor fraction occupied by metoprolol at 3 to 8 hours after drug intake was usually smaller, however (analysis of variance for repeated measures, P < .05) than that of the other drugs. Acebutolol occupied significantly larger fractions of beta 2-receptors (analysis of variance for repeated measures, P < .05) than did atenolol and metoprolol. Therefore, at an identical beta 1-receptor occupancy, the beta 2-receptor occupancy of acebutolol was larger than that of the other agents. Apparently, active metabolites decreased markedly the selectivity of acebutolol, but not that of metoprolol. The receptor occupancy of the agents was well in agreement with the literature concerning the selectivity, intensity, and time-course of drug actions after identical doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative beta-adrenoceptor blocking effects of propranolol, bisoprolol, atenolol, acebutolol and diacetolol on the human isolated bronchus

Five beta-adrenoceptor blockers, propranolol, acebutolol, diacebutolol, atenolol and bisoprolol, were tested for their antagonistic effect against isoprenaline on human isolated bronchi. The results showed (1) that only propranolol exerted a competitive antagonistic effect against isoprenaline (pA2 = 9.40 +/- 0.22, n = 7) whereas the other drugs did not, and (2) that, in the presence of beta-adrenoceptor blockers in the plasma concentrations reported after a single usual therapeutic dose, the doses of isoprenaline giving the same bronchodilator effect must be multiplied by 32.6, 5.51, 4.63, 2.82 and 1.95 respectively with propranolol, diacetolol, acebutolol, atenolol, and bisoprolol. It was concluded that (1) atenolol and bisoprolol were the least potent drugs at bronchial level in therapeutic plasma concentrations and (2) that tests performed on the human isolated bronchus might be a useful screening procedure for new drugs with potential activity on the airways.

Comparative effects of bisoprolol and acebutolol in smokers with airway obstruction

1. The effects of single oral doses of 10 mg bisoprolol and 400 mg acebutolol on respiratory function were studied in nine smokers with airway obstruction in a double-blind, placebo-controlled experiment. 2. The effects of the drugs were assessed by measuring specific airway conductance (sGaw) for 3 h after their administration and by studying their interaction with the bronchodilator response to inhaled salbutamol. 3. sGaw did not change for 3 h after bisoprolol or acebutolol administration. The bronchodilator response to inhaled salbutamol was not affected by bisoprolol but significantly reduced by acebutolol (P less than 0.05 vs placebo). 4. Under these conditions, bisoprolol behaves like a selective beta 1-adrenoceptor antagonist but acebutolol exhibits less beta 1-adrenoceptor selectivity.

Acebutolol: a review of its pharmacology, pharmacokinetics, clinical uses, and adverse effects

Acebutolol is a new hydrophilic, cardioselective beta-adrenergic-blocking agent that possesses partial agonist and membrane-stabilizing activities. In the treatment of mild to moderate essential hypertension, once-daily acebutolol as monotherapy provides effective control in a large majority of patients and produces a further reduction in blood pressure when used concomitantly with diuretics. Acebutolol is as effective as other beta-blocking agents, and in a large, double-blind, parallel study against propranolol was found to cause less reduction in heart rate, and fewer neurologic side effects and patient withdrawals due to adverse effects. Oral acebutolol is also effective in suppressing premature ventricular contractions, and in small numbers of patients generally beneficial results were obtained in supraventricular and ventricular arrhythmias with intravenous administration. These salutary effects are attributable to beta blockade. Controlled clinical trials documented the antianginal actions of oral acebutolol in chronic stable angina pectoris; its efficacy in this regard is comparable to that of other beta-blocking agents. The drug produces smaller decreases in heart rate and cardiac output and alterations in peripheral vascular hemodynamics than beta-blocking drugs without partial agonist activity, and because of its cardioselectivity, it may be used cautiously in patients with bronchospastic disease. Acebutolol has minimal metabolic effects and does not elevate levels of blood lipids during long-term therapy; high-density-lipoprotein cholesterol increased with acebutolol in a small number of patients.

Effects of esmolol on airway function in patients with asthma

In a double-blind, randomized, crossover study in ten patients with asthma, the effects on specific airway resistance of esmolol, a new ultra-short-acting beta 1-selective adrenoceptor blocker, were compared with those of placebo. Specific airway resistance was measured during increasing doses of esmolol infusion, during dry air provocation tests, and following isoproterenol inhalation. These same studies were later carried out on six of ten patients following intravenous propranolol infusion. All patients were able to tolerate the maximum dose of esmolol (300 micrograms/kg/min); treatment differences between esmolol and placebo were not found. In contrast, intravenous propranolol produced marked symptomatic bronchoconstriction after the lowest dose (1 mg) in two of six patients. Esmolol produced slight but statistically significant enhancement of patients' sensitivity to dry air provocation. Similarly, a slight but significant inhibition of bronchomotor sensitivity to isoproterenol was noted during esmolol infusion. After infusion of 5 mg of intravenous propranolol, one of four patients had a clinically significant increase in sensitivity to dry air. It is concluded that esmolol, because of its short duration of action and relative lack of effect on airway resistance, may be preferred over propranolol in patients with asthma who require treatment with an intravenous beta-blocking agent.

Comparative study of the respiratory effects of two beta 1-selective blocking agents atenolol and bevantolol in asthmatic patients

Seven asthmatic patients were given a single placebo tablet in a first test session and then in two subsequent double blind sessions they randomly received 400 mg bevantolol or 100 mg atenolol, with at least 2 days between each of the sessions. Neither beta-blocker had any significant effect on FVC as compared to the placebo. FEV 1, however, was significantly lower 2 and 3 h after atenolol or bevantolol; there was no significant difference between the effects of the two drugs on FEV 1. Peak expiratory flow rate was reduced by bevantolol but not by atenolol, the difference reaching significance after 3 h. Fenoterol inhalation at the end of each test session always enhanced pulmonary performance, but to a lesser extent after bevantolol than after placebo or atenolol. A slower heart rate was recorded 2, 3, and 4 h after bevantolol and 3 and 4 h after atenolol; the mean 2-h value was significantly lower with atenolol than with bevantolol. No patient suffered any adverse effect. Bevantolol may be slightly less selective than atenolol.

Ancillary pharmacologic properties of acebutolol: cardioselectivity, partial agonist activity, and membrane-stabilizing activity

Acebutolol, a new beta-blocking agent, possesses the ancillary pharmacologic properties of cardioselectivity and partial agonist and membrane-stabilizing activities. Compared to propranolol at equipotent doses, acebutolol produces less bronchoconstriction and preserves the bronchodilator response to isoprenaline. Similarly, acebutolol has less of an effect on peripheral vascular hemodynamics than does propranolol. Because of partial agonist activity, acebutolol produces a lesser reduction in heart rate and cardiac output than do propranolol and atenolol and has been found to have minimal effects on lipoprotein metabolism. Acebutolol may be the only beta-blocking agent that demonstrates some membrane-stabilizing activity at clinically achievable plasma concentrations. The ancillary pharmacologic properties of cardioselectivity and partial agonist activity are distinct and offer definite advantages to selected patients, particularly patients with respiratory disease, in whom cardioselective acebutolol, particularly at low doses, can minimize patient risk. The ancillary property of membrane-stabilizing activity may also guide therapy in selected patients.