Effects of single doses of alprenolol and two cardioselective beta-blockers (H 87-07 and H 93-26) on exercise-induced angina pectoris

Orthostatic response before and after nitroglycerin in metoprolol- and verapamil-treated angina pectoris

The orthostatic changes in heart rate (HR) and blood pressure (BP) were recorded in ten patients with stable angina pectoris before and after simultaneous sublingual nitroglycerin administration. All patients were examined three times: without other medication, during chronic metoprolol treatment, and during chronic verapamil treatment. Under control conditions, only minor changes were found in systolic BP following vertical tilting, while diastolic BP increased by approximately 10%. Nitroglycerin augmented these changes to some extent, while neither metoprolol nor verapamil caused significant changes. The orthostatic HR increase was considerably augmented by nitroglycerin. Verapamil treatment did not influence this response, while metoprolol caused significant reductions. These findings seem to explain why some few patients have observed severe orthostatic symptoms while taking nitroglycerin during treatment with beta-adrenergic blocking agents.

Beta-blockers alprenolol and carvedilol stimulate beta-arrestin-mediated EGFR transactivation

Recent evidence suggests that binding of agonist to its cognate receptor initiates not only classical G protein-mediated signaling, but also beta-arrestin-dependent signaling. One such beta-arrestin-mediated pathway uses the beta(1)-adrenergic receptor (beta(1)AR) to transactivate the EGFR. To determine whether beta-adrenergic ligands that do not activate G protein signaling (i.e., beta-blockers) can stabilize the beta(1)AR in a signaling conformation, we screened 20 beta-blockers for their ability to stimulate beta-arrestin-mediated EGFR transactivation. Here we show that only alprenolol (Alp) and carvedilol (Car) induce beta(1)AR-mediated transactivation of the EGFR and downstream ERK activation. By using mutants of the beta(1)AR lacking G protein-coupled receptor kinase phosphorylation sites and siRNA directed against beta-arrestin, we show that Alp- and Car-stimulated EGFR transactivation requires beta(1)AR phosphorylation at consensus G protein-coupled receptor kinase sites and beta-arrestin recruitment to the ligand-occupied receptor. Moreover, pharmacological inhibition of Src and EGFR blocked Alp- and Car-stimulated EGFR transactivation. Our findings demonstrate that Alp and Car are ligands that not only act as classical receptor antagonists, but can also stimulate signaling pathways in a G protein-independent, beta-arrestin-dependent fashion.

A clinical evaluation of sustained release metoprolol durules in the treatment of angina pectoris

A clinical comparison of the sustained release form of metoprolol, consisting of a 200 mg metoprolol durule, with 100 mg conventional metoprolol twice daily, has been carried out to assess the therapeutic control of ten patients with stable angina pectoris. Objective measurements of heart rate, blood pressure, and ECG recordings were assessed during exercise on a bicycle ergometer. Ten patients completed the 8-week double-blind study. There were similar changes in heart rate and blood pressure at rest and during exercise, both at 2 h and at 12 and 24 h postdose. Although similar exercise tolerance was achieved on both regimes, there was significantly less ST-segment depression at 24 h post durule, in comparison with the 12 h post conventional metoprolol reading, suggesting that metoprolol durules produce a more effective reduction in the degree of myocardial ischemia.

Comparison of once and twice daily sotalol in exercise-induced angina pectoris

The efficacy of chronic oral treatment with a total daily dose of 320 mg sotalol, given as a single or as two divided doses, was compared with placebo in a double-blind cross-over study of 12 patients with angina pectoris. Sotalol given once or twice daily significantly reduced heart rate and systolic and diastolic blood pressures at rest. The exercise heart rates were significantly decreased in both treatment groups. After sotalol 320 mg once daily, there was a greater reduction in the maximum exercise heart rate 2 h after taking the last tablet than after sotalol 160 mg b.i.d. The systolic blood pressure at the highest comparable work-load was significantly and equally reduced by sotalol both once and twice daily. Total work (watts X minutes in both sotalol treatment groups was significantly increased compared to placebo. There was no difference between the two sotalol dosage regimens. The peak plasma levels were higher after the once daily treatment, but the trough levels were similar for both regimens. No serious side effects were observed.

Hemodynamic effects of intravenous metoprolol

The hemodynamic effects of the cardioselective beta adrenergic blocking agent metoprolol, at a dose of 0.1 mg/kg body weight administered intravenously, were studied in 10 patients undergoing routine cardiac catheterization. The beta adrenergic blocking effect of the drug was confirmed by a highly significant reduction (53 percent, P less than 0.001) in the mean heart rate response to a challenge with isoproterenol, and by a mean heart rate rssponse to a challenge with isoproterenol, and by a highly significant reduction (73 percent, P less than 0.001) in the isoproterenol-induced increase in the first derivative of left ventricular pressure (dP/dt). An intrinsic negative inotropic effect was shown by a 43 percent reduction (P less than 0.05) in the response of mean left ventricular dP/dt when the heart rate was fixed by atrial pacing alone. With the combination of atrial pacing and isoproterenol, metoprolol produced a 48 percent reduction (P less than 0.01) in the response of mean left ventricular dP/dt, resulting from both the intrinsic depressor effect and the beta adrenergic blocking effect on the rate-independent beta agonist activity of isoproterenol. There was no significant change in right atrial, femoral arterial or left ventricular end-diastolic pressure; analysis of left ventricular angiograms performed during atrial pacing before and after metoprolol revealed no significant effect on angiographic ejection fraction, pressure-volume loops or diastolic compliance. In two patients improvement in segmental wall motion was noted, and no deterioration was seen in any patient. Metoprolol is an effective cardioselective beta adrenergic blocking agent that, under these conditions, reduces catecholamine-induced increases in heart rate and left ventricular dP/dt without significant alteration in ejection fraction, preload or afterload.

Mode of action of beta blockers in angina pectoris

The therapeutic effect of beta adrenoceptor blockers in angina pectoris can be ascribed to an inhibition of beta1 receptor mediated stimulation of heart rate and myocardial contractility, resulting in an improved oxygen supply-demand balance in the myocardium. When given in equipotent beta1 blocking doses, the nonselective blocker propranolol and the beta1 selective blocker metoprolol differ markedly as regards inhibition of adrenaline induced beta2 mediated vasodilatation. Only propranolol will inhibit this effect. After propranolol, adrenaline therefore elicits a haemodynamic effect pattern characterized by high peripheral vascular resistance, high arterial blood pressure, low cardiac output and increased cardiac size. In view of these findings it is suggested that a beta1 selective blocker may be a more efficient antianginal agent than a nonselective blocker in those patients in which the anginal attack is associated with a significant release of adrenaline. The clinical relevance of this hypothesis has not been tested.

An eighteen months' study of the clinical response to metoprolol, a selective beta1-receptor blocking agent, in patients with angina pectoris

Following an initial dose response study, metoprolol, a selective beta1-receptor blocking agent, was compared with equipotent dosages of propanolol in a double blind cross-over study, including exercise tolerance tests, on fourteen patients with angina pectoris. Long term therapy with metoprolol then followed until the seventy-second week. Patients performed 8% more total work on metoprolol with 15% more work recorded up to the onset of S-T depression, in comparison with propranolol. In the long term, ther was no significant difference in work performed when the daily dosage of metoprolol was changed from a q.i.d. to a b.d. regime. Metoprolol was shown to be an effective anti-anginal compound with good tolerance and safety, with gradual improvement in underlying myocardial ischaemia during long term treatment.

Assessment of metoprolol, a cardioselective beta-blocking agent, during chronic therapy in patients with angina pectoris

Ten patients with typical angina pectoris and without hypertension, congestive heart failure or other disease were treated with alternating four-week courses of metoprolol (alpha beta1 cardioselective beta-blocking agent), propranolol and placebo. Midway through each four-week period, drug dosage was doubled; thus, regimes were metoprolol, 150 and 300 mg/day, propranolol, 120 and 240 mg per day and placebo, 3 and 6 tablets per day. Serum concentrations of metoprolol increased with increasing dosage in a proportion very similar to that seen with propranolol. Statistically significant reductions in angina frequency/nitroglycerin consumption, and statistically significant increases in total work performed on a bicycle ergometer, were found with both active compounds when compared with placebo. No significant differences were noted between the two active compounds. Though most patients showed greatest improvement on the higher of the two drug dosages, three patients with metoprolol and two with propranolol responded best on the lower dose regime. Both compounds reduced heart rate at rest and during exercise. Neither reduced arterial pressure at rest, but both reduced arterial pressure during exercise. It is concluded that metoprolol is as effective as propranolol in the reduction of angina attacks and improvement in exercise tolerance during chronic therapy in patients with uncomplicated angina pectoris. It is now appropriate to study the effects of metoprolol in patients with coronary artery disease in whom the harmful effects of non-selective beta-blockade heretofore have precluded optimal therapy with beta-blocking drugs.