Effect of propranolol and metoprolol on parathyroid hormone and calcitonin secretions in uraemic patients

Nine uraemic patients not being treated by dialysis received intravenous propranolol 1 microgram/kg/min for 85 minutes after a priming dose of 1 mg. Fifteen days later, six of them received intravenous metoprolol 1.2 microgram/kg/min after a priming dose of 1.2 mg. Plasma concentrations of parathyroid hormone (PTH) and calcitonin fell significantly after propranolol but not after metoprolol, whereas no change in plasma concentrations of ionised calcium and phosphate occurred with either drug. Heart rate fell similarly with both drugs. The fact that propranolol acutely suppressed PTH and calcitonin secretion in uraemic patients indicates that further studies are warranted to assess the long-term effects of the drug on the secretion of these hormones and on renal osteodystrophy. The contrast between the responses to propranolol and metoprolol supports the concept that PTH and calcitonin secretion is modulated through specific beta 2-receptors.

Effects of metoprolol on effort angina during the postprandial state

To determine whether beta blockers prevent the more rapid onset of effort angina during the postprandial state, metoprolol 100 mg was given before and after an 800-calorie meal in 12 male patients with stable angina and coronary artery disease. Three graded treadmill exercise tests were done daily on 2 days. After an overnight fast the first test on each day was done after a placebo to detect day-to-day variations. The second test was done 90 min after metoprolol or placebo given orally in a double-blind randomized fashion. Immediately thereafter the patients ate their meal and did their third test 30 min later. There was no significant difference between the first test on each day. After placebo the postprandial state was associated with an earlier onset of effort angina (310 and 370 sec, p less than 0.01) and with greater heart rate and systolic blood pressure rises for any work load. After metoprolol, however, there was no significant difference between the pre- and postprandial findings. During the postprandial state metoprolol delayed the onset of angina more than placebo (385 and 310 sec) and positive electrocardiogram (310 and 228 sec) and induced lowering of maximal heart rate (120 and 144 bpm) and systolic blood pressure (157 and 187 mm Hg) (p less than 0.01). Metoprolol slowed the rapid onset of effort agina during the postprandial state.

Cortisol, growth hormone and prolactin responses to insulin-induced hypoglycaemia in hyperthyroid patients before and during beta-adrenoceptor blockade

Two beta-adrenoceptor blocking agents, metoprolol (beta-1-selective) and propranolol (non-selective), were used in the treatment of hyperthyroid patients. The response of pituitary stress hormones to insulin-induced hypoglycaemia was investigated before and during beta-adrenoceptor blockage. Treatment with metoprolol (n=10) or propranolol (n=10) produced no changes in the cortisol or prolactin responses to hypoglycaemia. Moreover the growth hormone response remained unaltered during treatment with metoprolol. A small, but statistically significant, augmentation of growth hormone response was obtained during treatment with propranolol. When twelve subjects, euthyroid after final conventional treatment (surger), radioiodine or thyrostatic drugs), were re-examined, the cortisol and prolactin responses were unchanged, although growth hormone concentrations reached a slightly higher maximum value (P less than 0.01). It was concluded that treatment with beta-blocking agents in hyperthyroid subjects has no clinically important influence on the release of pituitary stress hormones during hypoglycaemia.

Metoprolol kinetics and dose response in hypertensive patients

The kinetics and dose-response characteristics of metoprolol were examined in a series of hypertensive patients. In 14 the elimination half-life of metoprolol after single 100-mg doses (4.1 +/- 0.6 hr) was prolonged (p less than 0.05) after 6 to 12 wk of therapy (5.6 +/- 0.7 hr). In 5 patients receiving 100 mg twice daily evidence of nonlinear metoprolol kinetics emerged, because the area under the concentration-time curve at steady state was 86.8% more (p less than 0.02) than predicted from a single dose. Kinetic data from single doses of metoprolol appear to be a poor predictor of steady-state kinetics. Single metoprolol dosage also induced a fall (p less than 0.01) in blood pressure with pretreatment levels (163/108), reaching a minimum at 5 hr (133/189). During long-term therapy incremented doses of metoprolol between 100 and 600 mg/day in 34 hypertensive patients resulted in a relatively horizontal dose-response curve at doses above 200 mg/day.

Antihypertensive pharmacology

Although drug treatment of hypertension is associated with improved survival and decreased vascular complications, drug compliance is a major problem in the control of hypertension. All antihypertensive medications are associated with side effects; thus, it is a physician's responsibility to explain to each patient the side effects of the drugs he prescribes to treat hypertension, and to instill in the patient a sense of necessity for the treatment of hypertension. The choice of antihypertensive drug should be made based on each patient's lifestyle, overall health and ability to tolerate the drug. Ideally, the antihypertensive regimen should be simple, effective, convenient to take and have very few side effects.

Time course of blood pressure, pulse rate, plasma renin and metoprolol during treatment of hypertensive patients

Eleven patients were treated for essential hypertension with metoprolol (Selokén) for more than three months. The time course of changes in blood pressure, pulse rate and plasma renin activity was studied during treatment with an oral maintenance dose of 100 mg twice daily. Significant decreases in pulse rate, diastolic blood pressure and plasma renin activity were observed even after the first dose. The plasma concentration of metoprolol reached equilibrium after the second dose. After the third dose there was no further significant change in blood pressure. There was a significant correlation (p < 0.001) between the initial (after three doses) and final (after > 90 days) effect of metoprolol on blood pressure (r = 0.86 and 0.91 for systolic and diastolic blood pressure change, respectively).

The effect of metoprolol and atenolol on plasma high density lipoprotein levels in man

1. The effects of two beta-adrenoreceptor blocking drugs, metoprolol and atenolol, on plasma lipoproteins were studied in thirty-four patients using a single-blind cross-over design, with a 10-day placebo washout period between drugs. 2. Compared with placebo values, neither metoprolol nor atenolol influenced total plasma cholesterol levels, while total plasma triglycerides increased slightly. 3. Low density lipoprotein protein level remained unaltered, while high density lipoprotein (HDL) cholesterol and protein were significantly reduced by both beta-adrenoreceptor blockers. 4. The ratio of total cholesterol to HDL cholesterol was increased by both drugs. 5. The data suggest that patients taking these drugs over many years may be exposing themselves to increased vascular risk, despite other anticipated benefits from such therapy.

[Clinical trials of various glaucoma drugs acting on the adrenergic system (author's transl)]

The authors summarize findings in a clinical trial of the betablockers Timolol and Metoprolol, as well as the effectiveness of various concentration of the combination preparation Guanethidine-Adrenaline. In the trial Timolol proved to be the almost ideal drug for glaucoma therapy. However, as a pressure-lowering agent the guanethidine-epinephrine combination is more effective. Metroprolol, which is a pure beta 1-blocker, is probably preferable to Timolol in asthmatic patients.

Newer antihypertensive agents

There are very few areas of clinical pharmacology being pursued as vigorously as hypertension. Numerous new drugs are being discovered and tested both in United States and overseas. The most promising new antihypertensive drugs seem to fall into the angiotensin-renin blocker group and those affecting the sodium-volume axis in hypertensive patients. We can look forward to newer agents that are efficacious as monotherapy and on a daily or twice daily dosage regimen for the treatment of the vast majority of hypertensive patients. There is further hope that preoperative evaluation with angiotensin blockers in patients with renovascular hypertension may improve the predictability of successful renal bypass surgery.

A comparison of oral metoprolol and propranolol in patients with chronic bronchitis

A double-blind study of oral metoprolol and propranolol in nine patients with chronic bronchitis (Medical Research Council definition) showed no appreciable deterioration in lung function or significant differences between the two drugs.

Insulin release and carbohydrate tolerance in hyperthyroid patients during non-selective or selective beta-1-adrenoceptor blockade

The insulin release and the glucose disappearance rate (K-value) during an iv glucose tolerance test were evaluated in 20 hyperthyroid patients before and during treatment with either a non-selective (propranolol, n = 10) or a selective (metoprolol, n = 10) beta-1-adrenoceptor blocking agent. Mean daily doses were 240 mg of propranolol and 280 mg of metoprolol, administered four times daily for 10 to 14 days. The insulin increase after glucose injection remained unchanged during treatment with each drug. Fasting blood glucose concentrations and the K-values were not altered during treatment. Sixteen patients were re-investigated 10 to 36 weeks later when euthyroid due to treatment by surgery, thyrostatic drugs or radioiodine. In the euthyroid state mean serum insulin concentrations after the glucose load were not significantly different from the values found when the patients were hyperthyroid. However, mean fasting blood glucose concentrations decreased from 5.5 mmol/l to 5.0 (P less than 0.01) and the mean K-value increased from 1.5 to 2.0 (P less than 0.05) when the patients were euthyroid. It is concluded that short-term treatment of hyperthyroid patients with non-selective or selective beta-1-adrenoceptor blocking agents does not impair the glucose stimulated insulin secretion or the carbohydrate tolerance.

Experiences with metoprolol Durules, a slow-release formulation in hypertension

The antihypertensive effect and the tolerability of metoprolol Durules have been studied in fifty-five patients with mild to moderate hypertension. The patients' diastolic blood pressure was greater than or equal to 95 mm Hg in order to qualify for entry. Thirty-seven out of fifty-three patients completing the study (70%) were treated with metoprolol Durules monotherapy throughout the study. The mean blood pressure was reduced from 153/101 to 138/92 mm Hg after metoprolol Durules compared to placebo (p less than 0.001). Twenty-seven patients received one Durules daily and ten patients received two Durules daily as the final dose. Of the sixteen patients not responding on metoprolol Durules, six patients achieved satisfactory control, i.e. a diastolic blood pressure below 95 mm Hg, when given 200 mg metoprolol + 25 mg hydrochlorothiazide (HCT). The results indicate that most patients with mild or moderate hypertension can be controlled with metoprolol Durules monotherapy given one daily. The addition of HCT gives a significant benefit in moderate hypertension, where metoprolol monotherapy is not sufficient.

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.