The effects of propranolol and acebutolol on left ventricular function and coronary haemodynamics in the conscious dog with myocardial ischaemia

Effects of KRN4884 (a novel K+ channel opener), levcromakalim, nilvadipine and propranolol on endothelin-1-induced heart disorders in anesthetized rats

The effects of KRN4884 (5-amino-N-[2-(2-chrolophenyl)ethyl]-N'-cyano-3-pyridinecarboxa midine), a novel K+ channel opener, on the electrocardiogram changes caused by the intracoronary administration of endothelin-1 (ET-1) were studied in anesthetized rats and compared with the effects of levcromakalim, a K+ channel opener; nilvadipine, a Ca2+ antagonist; and propranolol, a beta-adrenoceptor antagonist. KRN4884 (50 microg/kg, i.v.) and levcromakalim (300 microg/kg, i.v.) inhibited the ST segment elevation and the development of arrhythmias induced by ET-1 (5 microg, i.c.) and decreased the incidence of death. Nilvadipine (300 microg/kg, i.v.) and propranolol (1000 and 3000 microg/kg, i.v.) each prevented the ST segment elevation, but the suppressions of the occurrence of arrhythmias produced by nilvadipine and propranolol were less than that shown by KRN4884. KRN4884 (30 and 50 microg/kg, i.v.), levcromakalim (100 and 300 microg/kg, i.v.) and nilvadipine (100 and 300 microg/kg, i.v.) significantly decreased the mean blood pressure in a dose-dependent manner, but propranolol did not. The heart rate was decreased by nilvadipine (100 and 300 microg/kg, i.v.) and propranolol (1000 and 3000 microg/kg, i.v.), but was not affected by KRN4884 (30 and 50 microg/kg, i.v.) or levcromakalim (100 and 300 microg/kg, i.v.). These results suggest that pretreatments with KRN4884 and levcromakalim are more effective on ET-1-induced electrocardiogram changes than those with nilvadipine and propranolol.

Effect of intravenous propranolol on coronary vasomotion at rest and during dynamic exercise in patients with coronary artery disease

Coronary vasomotion was studied at rest and during bicycle exercise with biplane quantitative coronary arteriography in 28 patients with coronary artery disease. Patients were divided into two groups; the first 18 patients served as controls (group 1), and the next 10 patients were treated with propranolol 0.1 mg/kg, which was infused intravenously before exercise (group 2). Luminal area of a normal and a stenotic vessel segment was determined at rest, during supine bicycle exercise, and 5 minutes after sublingual administration of 1.6 mg nitroglycerin after exercise. In group 1, the normal vessel showed vasodilation (+16%, p less than 0.001) during exercise, whereas the stenotic vessel segment showed vasoconstriction (-31%, p less than 0.001). After sublingual administration of nitroglycerin, there was coronary vasodilation of both normal (+36%, p less than 0.001 vs. rest) and stenotic (+20%, p less than 0.001) vessel segments. Patients with angina pectoris during supine exercise (n = 10) had significantly (p less than 0.05) more vasoconstriction (-36%) than patients without angina (-23%). In group 2, intravenous administration of propranolol at rest was associated with a decrease in luminal area of both normal (-24%, p less than 0.001) and stenotic (-43%, p less than 0.001) vessel segments; however, during subsequent exercise, both normal (-2%, p = NS vs. rest) and stenotic (-3%, p = NS vs. rest) vessel segments dilated when compared with the measurements after propranolol. Administration of nitroglycerin further increased luminal area of both vessel segments (normal segment, +23%, p less than 0.001; stenotic segment, +46%, p less than 0.001 vs. rest). It is concluded that dynamic exercise in patients with coronary artery disease is associated with coronary vasodilation of the normal and vasoconstriction of the stenotic coronary arteries. Patients with exercise-induced angina had significantly more stenosis vasoconstriction than patients without angina although minimal luminal area at rest was similar. Intravenous administration of propranolol is accompanied by a significant decrease in coronary luminal area of both normal and stenotic vessel segments at rest, which is overridden by dynamic exercise and sublingual nitroglycerin. The reduction in myocardial oxygen consumption and the prevention of exercise-induced stenosis vasoconstriction might explain the beneficial effect of beta-blocker treatment in most patients with coronary artery disease.

Evaluation by 31P NMR of the effects of acebutolol on the ischaemic isolated rat heart

We used 31P NMR spectroscopy to study the effect of acebutolol on the metabolic disturbances caused by ischaemia in the isolated rat heart. The intracellular acidosis and high-energy phosphate compound depletion induced by global low-flow ischaemia were significantly attenuated in the presence of acebutolol 2.7 X 10(-5) and 1.35 X 10(-4) M. The drug displayed no significant effect either at the 5.4 X 10(-6) M concentration or when administered as pretreatment to the animals (50 mg X kg-1, 120 and 60 min before isolating the heart). Since acebutolol had no effect on the contractility of the isolated rat heart at the 2.7 X 10(-5) M concentration the present results suggest that the mechanisms through which acebutolol exerts its effects on energy metabolism are not related to a reduction of cardiac work. The possible contribution of the membrane-stabilizing property of the drug is suggested by the fact that high concentrations are needed and that a short pretreatment had no effect.

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.

Acebutolol. A review of its pharmacological properties and therapeutic efficacy in hypertension, angina pectoris and arrhythmia

Acebutolol is a cardioselective beta-adrenoceptor blocking drug possessing both partial agonist (intrinsic sympathomimetic) and membrane stabilising activity. In hypertension, it can be administered once or twice daily with equal effectiveness, and has been as effective at lowering blood pressure as propranolol, diuretics, and other beta-blocking drugs (metoprolol, labetalol and atenolol) and more effective than methyldopa. Acebutolol has a significantly smaller effect on resting heart rate than propranolol, metoprolol and atenolol, although direct comparisons with drugs with intrinsic sympathomimetic activity have yet to be undertaken. In both angina and arrhythmia, when administered twice daily it has been as effective as standard therapeutic agents. The side effect profile of acebutolol appears to be comparable to that of other cardioselective beta-blockers. Its relative cardio-selectivity, partial agonist and membrane stabilising activity, hydrophilicity, and considerable extrarenal excretion may offer advantages over some beta-blocking drugs in specific patients. Choosing a beta-blocking agent, however, should be made with a knowledge of pharmacodynamic and pharmacokinetic properties of the various agents and careful consideration of how such properties may be of benefit to an individual patient.