Metoprolol--a new cardioselective beta-adrenoceptor blocking agent for treatment of tachyarrhythmias

The antiarrhythmic effect of the cardioselective beta-adrenoceptor blocking agent metoprolol, given intravenously, was studied in 44 patients with various tachyarrhythmias, including patients with congestive heart failure and signs of digitalis intoxication. All patients with atrial tachycardia (12 cases) reverted to normal sinus rhythm. In 3 out of 18 patients with atrial fibrillation, sinus rhythm was restored, and in the others there was a significant reduction in ventricular rate. In 6 of 10 patients with ventricular ectopic beats, and 1 of 2 patients with ventricular tachycardia, the ectopic rhythm was abolished. The drug was well tolerated, without any significant changes in blood pressure, even by patients with signs of digitalis intoxication and varying degrees of pulmonary or peripheral circulatory congestion. Metoprolol is of clinical value for treatment of tachyarrhythmias, especially those of supraventricular origin.

Antihypertensive effect and tolerability of metoprolol during long-term treatment: a multicentre study

One hundred and forty-seven patients with essential hypertension participated in this multicentre study. The results indicate that metoprolol in a dosage of 150-450 mg daily is an effective and well tolerated therapy both in patients previously untreated and in patients unsatisfactorily treated with other antihypertensive agents.

South African multicentre study of metoprolol and propranolol in essential hypertension

Ninety-three patients diagnosed as essential hypertensives, WHO stage I or II, entered this double-blind trial comparing 2 dose levels of CGP 2175-H 93/26 (metoprolol) with 2 doses of propranolol. Treatment on active medication was maintained for 6 weeks and was started after a 2-week washout and a 2-week placebo period. Twelve patients dropped out of the trial for reasons not related to the drugs and 1 patient was regarded as a therapeutic failure. Efficacy was assessed by measuring the diastolic and systolic blood pressure, pulse rate and by noting any significant ECG changes. All treatments reduced and maintained a lower blood pressure. However, a reduction with 360 mg propranolol per day was not statistically significant. Metoprolol 120 mg/d was significantly superior to propranolol 240 mg/d in holding the diastolic supine blood pressure at less than or equal to 90 mmHg. Metoprolol 120 mg/d and 210 mg/d pooled results were significantly superior to the propranolol 240 mg/d and 360 mg/d pooled data in maintaining a diastolic blood pressure of less than or equal to 90 mmHg. All treatments were well tolerated and in no case was it necessary to withdraw owing to adverse effects. No significant difference was detected between the treatments with respect to therapeutic emergent symptoms and signs. Laboratory results remained normal with all treatments.

Anti-hypertensive effect of metoprolol in spontaneously hypertensive rats

1. Oral and intravenous administration of metoprolol to adult spontaneously hypertensive rats (SHR) with established hypertension lowered arterial blood pressure within 4 days of treatment. 2. Steady state plasma concentrations of metoprolol were similar to those of patients during anti-hypertensive treatment with this drug. 3. The neuroeffector function of portal veins of SHR treated orally for 14 days or intravenously for 4 days was not impaired when studied in vitro. This is in contrast to previous findings after long-term treatment. 4. It is concluded that the anti-hypertensive effect of metoprolol in SHR in many respects resembles that observed in patients. It is suggested that impairment of vasomotor nerve control may contribute to the anti-hypertensive effect of beta-adrenoreceptor antagonists.

A controlled study on the anti-hypertensive effect of a new beta-adrenoreceptor-blocking drug, metoprolol, in combination with chlorthalidone

1. A double-blind cross-over evaluation of the anti-hypertensive effect of metoprolol vs placebo was carried out in a series of twenty-three patients with mild or moderate essential hypertension who were receiving 25 mg of chlorthalidone daily as their basic treatment. An individually determined dose of metoprolol (75-300 mg) was used. 2. Metoprolol, as compared with placebo, produced a statistically significant reduction of blood pressure, both in supine and standing positions. 3. During the double-blind cross-over study mild side effects were more common at the beginning of metoprolol/chlorthalidone treatment than during placebo/chlorthalidone, but these tended to diminish or disappear with time. 4. Metoprolol in combination with chlorathalidone appears to be an effective and well-tolerated treatment for mild and moderate hypertension in patients not responding to chlorthalidone alone.

[Hemodynamic changes under metoprolol compared to propranolol in hypertensive patients]

The effect of the new beta-receptor-blocking drug metoprolol on hemodynamics and plasma renin activity was studied at rest and during exercise. 5 patients with essential hypertension were investigated before, 4 weeks after and 8 weeks after oral treatment (3 X 50 mg day). The results were compared to data of 5 patients under propranolol matched according to age, arterial blood pressure, and renin concentration. Metoprolol leads to a significant fall in renin and heart rate, whereas cardiac index is depressed only during exercise. Peripheral resistance remains unchanged and left ventricular filling pressure rises slightly. This results in a slight fall in arterial blood pressure. In comparison with propranolol the hemodynamic and renin patterns under metoprolol are similar, the only difference being the slighter fall in blood pressure due to a less depressed cardiac index.

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.

Comparison of metoprolol as hydrochlorothiazide and antihypertensive agents

A crossover comparison of metoprolol and hydrochlorothiazide has been performed in 20 patients with mild hypertension. Both drugs caused almost identical statistically significant reduction in blood pressure of about 20 mm Hg systolic and 15 mm Hg diastolic. The side effects during active therapy were few and mild, but 5 patients experienced subjective symptoms during the first few days following abrupt withdrawal of metoprolol, namely general malaise, palpitations, headache, sweating and tremor. The symptoms were more pronounced in the standing position and disappeared at once on resumption of beta-blocker therapy, or gradually over 5 - 7 days when placebo tablets were given. In 11 of the 20 patients hydrochlorothiazide produced subnormal serum potassium levels and potassium supplements were given. The serum uric acid level was also significantly increased during hydrochlorothiazide 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.

Comparative study of metoprolol and alpha-methyldopa in untreated essential hypertension

The hypotensive actions of metoprolol and alpha-methyldopa have been compared in 37 men with previously untreated essential hypertension; 36 belonged to stage 1 and 1 to stage 2 of the WHO classification. After four weeks of placebo treatment the patients were randomly allocated to treatment with either of the two drugs. Treatment was started with metoprolol 75 mg daily or alpha-methyldopa 375 mg and was doubled after eight weeks. Satisfactory blood pressure control was defined as systolic blood pressure below 160 mm Hg and diastolic below 95 mm Hg. The patients were examined every four weeks and in those with unsatisfactory control the dose was gradually increased up to a maximum daily dose of metoprolol 450 mg or alpha-methyldopa 2250 mg. The trial lasted for 24 weeks after randomization. Five patients dropped out of the study. After six months, satisfactory blood pressure control was recorded in 16 out of 17 patients and 14 out of 15 patients treated with metoprolol and alpha-methyldopa, respectively. The average reduction in blood pressure produced by the two drugs was comparable. One patient in the alpha-methyldopa group developed drug exanthema and two patients a positive Coombs' test. Other side effects were few and did not differ between the two compounds.