A comparison between once-daily and twice-daily administration of metoprolol in the management of hypertension

The efficacy of metoprolol as an antihypertensive agent was assessed in 20 previously untreated Asian patients with mild to moderate hypertension. After a 4-week run-in period when placebo therapy was given, the patients were given oral metoprolol at a starting dosage of 100 mg twice daily. The dosage of metoprolol was increased at fortnightly intervals until either satisfactory blood pressure control, defined as a diastolic blood pressure of less than 90 mmHg or a greater than 10% fall in pre-treatment diastolic blood pressure, was achieved or a total of 400 mg metoprolol was reached. All 20 patients had satisfactory control of their blood pressures on a twice-daily regimen and the average dosage of metoprolol required was 200 mg daily. For the second part of the study, the medication was changed to a once-daily regimen at the same total dosage of metoprolol. Final efficacy of once-daily therapy was assessed after 8 weeks of treatment. All blood pressure and pulse rate reductions were significant (P < 0.001) from the placebo phase. However, twice-daily and once-daily readings were not significantly different from each other. No side-effects were reported during the study.

Evidences supporting an increased sympathetic tone and reactivity in a subgroup of patients with essential hypertension

Several experimental evidences have shown that, under standarized conditions, circulating catecholamines (CA) or norepinephrine (NE) levels can be used as a valid index of the sympatho-adrenal activity in animal and man. This approach in the study of hypertensive patients has permitted to uncover that about 50% of patients with labile hypertension and about 30% of patients with stable hypertension had elevated CA levels at rest for 20 minutes in the supine position. The increased CA levels were mainly due to a rise in NE in stable hypertension and to a rise in epinephrine (E) in labile hypertension. On the basis of circulating CA levels, the hypertensive patients were divided into hyperadrenergic (CA levels above normal range) and normoadrenergic (CA levels within the normal range) subgroups. The hyperadrenergic labile or stable hypertensive subgroups were found to be also characterized by an enhanced CA or NE increase in response to change in position from supine to standing, by a faster heart rate and by an increased myocardial contractility, while these parameters were normal in the normoadrenergic subgroups. These findings support therefore the existence of an increased sympathetic tone and reactivity in association with hyperkinetic cardiac functions in an important population of hypertensive patients. In response to two weeks treatment with beta-blockers (either propranolol or metoprolol) hyperadrenergic stable hypertensive patients were found to be more responsive to this therapy than normoadrenergic patients although both groups had the same initial blood pressure. Moreover, this treatment lowered basal NE or CA levels and restored the enhanced CA or NE response to change in position toward normal in hyperadrenergic patients while it did not modify significantly circulating supine or standing CA and NE in normoadrenergic patients. These findings strongly support a participation of the sympathetic system in the maintenance of an elevated blood pressure in hyperadrenergic patients and raise the possibility of using a more rational approach in the therapy of hypertension.

Comparison of propranolol and metoprolol in the management of hyperthyroidism

1 Propranolol and metoprolol were both effective in controlling the symptoms and signs of hyperthyroidism. 2 Propranolol caused a highly significant increase in serum reverse T3 concentrations with lesser changes in other serum thyroid hormone levels, whereas metoprolol did not have this effect. 3 Steady-state plasma propranolol and metoprolol levels showed marked inter-individual variation. Metoprolol concentrations showed relatively little intra-individual variability, and could be related to the clinical efficacy of the drug, whereas no such relationship was demonstrated for propranolol.

Influence of selective and non-selective beta-adrenoreceptor blockade on the haemodynamic effect of adrenaline during combined antihypertensive drug therapy

1. Haemodynamic effects of adrenaline were studied in 27 hypertensive patients, succesively during treatment with propranol and metoprolol. In 12 patients beta-adrenoreceptor blockade was combined with diuretics and in 15 patients the blockade was combined with vasodilators. 2. During propranolol adrenaline caused a marked pressor effect: there was a considerable rise in systolic as well as in diastolic blood pressure and a marked fall in heart rate. During metoprolol there was only a slight rise in blood pressure and an increase in heart rate. 3. Forearm blood flow was decreased by adrenaline during propranolol and was increased during metoprolol. Calculated vascular resistance showed opposite changes. 4. Results were essentially the same when beta-adrenoreceptor blockade was combined with diuretics or with vasodilators and did not differ from previous results obtained in patients treated by blockade alone. 5. If adrenaline infusion can be considered as a model for acute stress, our results seem to favour a selective beta 1-adrenoreceptor blocking agent over a non-selective one, even when the blocker is combined with a diuretic or a vasodilator.

Angiotensin II blockade during combined thiazide-beta-adrenoreceptor-blocker treatment

1. Sixteen patients (11 male, five female), median age 41 years, with essential hypertension insufficiently controlled by hydrochlorothiazide (75 mg/day; diastolic blood pressure greater than or equal to 100 mmHg), were studied. 2. Plasma renin concentration [renin], plasma angiotensin II concentration ([ANG II]), plasma volume and exchangeable sodium (NaE) were determined, and a saralasin infusion (5.4 nmol min-1 kg-1) was carried out while the patients were on thiazide alone and, in 14 cases, 3 months after addition of a beta-adrenoreceptor blocker (propranolol, six, metoprolol, six, and atenolol, two patients). 3. On thiazide alone, saralasin caused a significant decrease in mean arterial blood pressure in 12 out of 16 patients. The saralasin response was closely related to pre-saralasin plasma [ANG II] (r = 0.73, P less than 0.01). Plasma [renin] and [ANG II] were higher than normal in the group as a whole. 4. After addition of a beta-adrenoreceptor blocker systolic and diastolic blood pressure decreased from 164/109 mmHg to 136/94 mmHg. Plasma [renin] and [ANG II] decreased by 40 and 58% respectively. At this point, saralasin caused no significant change in mean arterial pressure. No close correlation was found between plasma [renin] or [ANG II] or saralasin response on thiazide treatment and changes in blood pressure during subsequent thiazide/beta-adrenoreceptor-blocker treatment. Plasma volume and NaE did not change significantly. 5. In patients with thiazide-induced stimulation of the renin-angiotensin system, addition of a beta-adrenoreceptor blocker leads to suppression of the system and, at the same time, ANG II-dependence of blood pressure disappears. This contributes to the antihypertensive effect of beta-adrenoreceptor blockers in this particular situation.

One year follow-up of hyperuricaemic hypertensive patients treated with tienilic acid or a diuretic with or without uric acid-lowering drugs

1. Fifty-four hypertensive, hyperuricaemic patients were pair-matched for age, sex and current therapy (diuretic, uric acid-lowering drug).

2. One member of each pair was randomly assigned to continue on the previous therapy and the other member to treatment with tienilic acid (ticrynafen). Routine potassium chloride supplements were given only to subjects who were or had previously been on uric acid-lowering drugs.

3. Blood pressure control was equally good in the tienilic acid-treated and control groups. Serum uric acid was significantly lower in patients treated with tienilic acid.

4. In patients (32) not given supplements of potassium chloride, mean serum K+ did not fall but in four patients (three on tienilic acid, one on cyclopenthiazide) serum K+ fell to 3·5 mmol/l or less and potassium chloride was added.

5. Liver-function tests changed from pretrial results in nine patients. In eight of these (four on tienilic acid and four in the control group) minor rises in alkaline phosphatase only occurred. In the ninth patient, who was also taking metoprolol, serum aspartate transaminase rose markedly after 2 months and fluctuated for 4 months. Eventually there were also rises in alkaline phosphatase and bilirubin; these reverted to normal after stopping tienilic acid.

Effect of exercise in hypertension controlled with metoprolol or methyldopa

1. The adequacy of the control of essential hypertension during exercise was studied in patients whose resting blood pressure had been controlled for 1 year with either metoprolol or methyldopa. 2. Systolic blood pressure increased with exercise in both groups, the increase being significantly less in the metoprolol group than in the methyldopa group.

Effects of metoprolol on blood pressure and plasma renin activity in thiazide-resistant hypertensive patients

Twenty patients with mild to moderate hypertension whose blood pressures were not adequately controlled by a thiazide diuretic were treated for 4 wk with metropolol. Normotension (diastolic pressure less than 90 mm Hg) or reduction in diastolic pressure of at least 10 mm Hg was achieved in 12 of the patients 1 wk after metoprolol (200 mg/day) was added to the hydrochlorothiazide (100 mg/day) regimen. In the other 8 patients, pressure reduction was attained with larger doses (300 to 400 mg/day) of metoprolol. After 1 wk of combined therapy, heart rate decreased by 11% (p less than 0.001) and plasma renin activity (PRA) decreased 48% (p less than 0.001). The individual changes in mean blood pressure did not correlate with either the premetoprolol PRA level (r = 0.14) or the changes in PRA after metoprolol (r = 0.03) but did correlate with steady-state metoprolol plasma levels (r = 0.61, p less than 0.01). Pressure and heart rate reductions were sustained during the last 3 wk of combined therapy but the PRA decrease did not persist; levels gradually rose to near control by the fourth week. Urinary sodium excretion was not consistently changed on metoprolol therapy.

[Beta-receptor blocking drugs and the bronchial system. A comparative study of pindolol and metoprolol (author's transl)]

Effects of the beta 2-receptor stimulating drug fenoterol were investigated after administration of beta-receptor blocking agents in 12 patients with obstructive respiratory disease and a hyperreactive bronchial system (positive acetylcholine test). In a double blind trial pindolol (universal beta-receptor blocking drug) and metoprolol (a cardioselective substance) were compared after administration of equally effective doses of 5 and 100 mg respectively. Whole-body plethysmography showed that both beta-receptor blocking drugs caused no bronchial constriction; the bronchodilating effects of fenoterol were not reduced. These findings must cast doubt on the differentiation between cardioselective and non-cardioselective beta-receptor blocking agents as far as practical therapeutic implications are concerned.

Red cell changes in hyperthyroidism

The Coulter 'S' red cell profile was studied prospectively in 100 untreated non-anaemic hyperthyroid patients and followed up in 52 of them until they had become euthyroid with radio-iodine or carbimazole treatment. Serial haematological data were also obtained in 23 hyperthyroid patients during treatment with beta-adrenoreceptor blocking drug alone. The most significant finding was a low mean corpuscular volume (MCV) which was invariably present throughout the hyperthyroid state. Treatment with beta-adrenoreceptor blocking drugs did not significantly alter any of the red cell parameters. On the other hand, the MCV increased and was restored to normal with radio-iodine or carbimazole treatment although there was a lag period of about 6--8 weeks between achieving the euthyroid state and the normalisation of this red cell index. While none of the patients were aneaemic, the haemoglobin level rose significantly following effective anti-thyroid treatment. It is suggested that measurement of the MCV may have a useful role in the diagnosis of hyperthyroidism. 2 possible mechanisms leading to the observed red cell changes in hyperthyroidism are postulated.

Slow-release metoprolol in angina pectoris. A comparative study of a cardioselective beta-blocking drug, metoprolol, in ordinary and slow-release tablets (Durules) in the treatment of angina pectoris

A double-blind cross-over study was undertaken to compare the effects of ordinary metoprolol tablets (tablets) 0.1 g b.i.d. and metoprolol slow-release tablets (Durules) 0.2 g once daily in 16 patients with angina pectoris. Initially, the patients were treated with placebo for 2 weeks, and then during the cross-over periods with either 1 tablet morning and evening or 1 Durules in the morning and 1 placebo in the evening. Standardized bicycle ergometer exercise tests with heart rate and blood pressure measurements were performed 2 hours after placebo, 2 hours after tablets and Durules, 12 hours after tablets and 24 hours after Durules. The patients kept diaries of their anginal attacks throughout the study. There were no statistically significant differences in total work between tablets and Durules when the values at 12 hours and 24 hours were compared. However, total work was significantly greater at 2 hours and at 12 hours after tablets and 24 hours after Durules than after placebo. Heart rate and systolic blood pressure during exercise were significantly decreased 24 hours after Durules compared to placebo. The heart rate was, however, lower 12 hours after tablets than 24 hours after Durules (p less than 0.05), although this slight difference in the degree of beta-blockade did not seem to be of clinical importance in these patients.

Effects of beta-adrenoreceptor antagonists on sino-aortic baroreflex sensitivity and blood pressure in hypertensive man

1. Sensitivity of the sino-aortic baroreflex was investigated before and after acute (23 patients) and chronic (23 patients) beta-adrenoreceptor antagonism in patients with essential hypertension. 2. Sensitivity was inversely related to age (r = -0.60) and systolic blood pressure (r = -0.46); a positive relationship was noted between sensitivity and initial pulse intervals (r = 0.40). 3. Sensitivity increased significantly in patients less than 40 years of age after chronic treatment. No change occurred after acute treatment or in older patients treated chronically. 4. The fall in ambulatory intra-arterial blood pressure after chronic treatment was unrelated to alteration of baroreflex sensitivity.

Series on pharmacology in practice. 2. Antiarrhythmic drug therapy

The selection of appropriate antiarrhythmic drug therapy depends on a knowledge of the drugs available, their spectrum of action, their pharmacokinetics, and their major side effects. It is important to know how the pharmacokinetics of a drug vary with different disease states so that appropriate adjustments to dosage can be made. Drugs with similar actions can be assigned into groups, and five different groups can be identified. The commonly used antiarrhythmic drugs are reviewed, and some of the newer drugs are discussed.

Influence of metoprolol on hemodynamics and respiratory function in asthmatic patients

Studies of metoprolol in asthmatic patients showed beta 1-selective blocking properties on the adrenergic receptor. Metoprolol in a dose of 40 mg given orally to 9 asthmatic patients significantly decreased the pulse rate at 60 and 120 minutes and the systolic blood pressure at 120 minutes but did not cause any increase of respiratory impedance, measured by the forced oscillation technique. A double-blind test was carried out to compare the effects of metoprolol and inactive placebo on the respiratory response to isoproterenol in 24 asthmatic patients. In the metoprolol group, systolic blood pressure decreased significantly and pulse rate at rest also tended to decrease. There was no significant difference between the metoprolol and placebo groups in the respiratory response to an isoproterenol aerosol.