Effect of alprenolol on blood pressure and plasma renin activity in hypertensive patients

A controlled study on the antihypertensive effect of a new beta-adrenergic receptor blocking drug, metoprolol, in combination with chlorthalidone

A double-blind crossover evaluation of the antihypertensive effect of metoprolol v. placebo was carried out in a series of twenty-three patients with mild or moderate essential hypertension who were receiving chlorthalidone (25 mg daily) as their basic treatment. An individually titrated metoprolol dosage (75-300 mg) was used. The double-blind crossover study consisted of two 3-month periods during which the patients received either metoprolol or placebo in addition to chlorthalidone. Metoprolol, as compared with placebo, produced a statistically significant reduction of blood pressure, both in supine and standing positions. Normotension was achieved during metoprolol-chlorthalidone treatment in twenty-two of the twenty-three patients, but during placebo-chlorthalidone treatment in only twelve of the twenty-three patients. During the double-blind crossover study mild side-effects occurred during metoprolol-chlorthalidone treatment in fourteen patients during first month, in twelve patients during second month and seven patients during third month. During placebo-chlorthalidone treatment side effects occurred in seven, six and seven patients, respectively. In conclusion, metoprolol caused a significant fall in blood pressure when given to patients already receiving chlorthalidone. Metoprolol in combination with chlorthalidone appears to be an effective and well-tolerated treatment for mild and moderate hypertension in those patients not responding to chlorthalidone alone.

Relationship between plasma aldosterone concentration and plasma potassium in patients with essential hypertension during alprenolol treatment

Plasma aldosterone concentration (PAC), plasma renin concentration (PRC), plasma potassium, plasma sodium and blood pressure (BP) have been measured in 22 patients with essential hypertension before and after treatment for one month with alprenolol. PAC, PRC and BP decreased and plasma potassium increased significantly during treatment. Plasma sodium, however, was unchanged. Changes in PAC were inversely correlated to changes in plasma potassium. No relationship could be demonstrated between PAC and plasma sodium. Mean BP was inversely correlated to PAC during alprenolol treatment, but bot before treatment. No relationship was found between changes in BP and changes in PRC. The results suggest that plasma potassium is an important regulatory factor for aldosterone secretion during alprenolol treatment. Other factors, however, must have a modulating influence and since the renin- angiotensin system is not suppressed to very low values, this system is possibly the most important of these factors. It is suggested that aldosterone secretion is not of primary importance in BP regulation during alprenolol treatment.

Prognostic value of renal vein renin determination in suspected renovascular hypertension

Surgical correction of unilateral renal artery stenosis was performed in 31 hypertensive patients. Preoperative renal vein renin ratios (RVRR) before and after dihydralazine stimulation were measured in all patients. Postoperative blood pressure were normal in 12, improved in 17 and unchanged in 2 patients. Six patients did not have renin lateralization, but all were cured or improved after surgery. RVRR was a poor predictor of the results of surgery in patients with unilateral renal artery stenosis.

Hemodynamic effects of diuretic therapy in hypertension

The antihypertensive effect of diuretics is well documented. At least some preserved kidney function seems to be necessary to achieve a demonstrable effect. The importance of fluid volume reduction for the antihypertensive effect of these drugs during long-term treatment is however uncertain. The effects on central hemodynamics vary according to the literature, but the blood pressure reduction in responders (delta MAP greater than 10%) may primarily be explained by a reduction of the total peripheral vascular resistance. The peripheral circulation is influenced in the same way. Sometimes a flow reduction is observed, and sometimes a resistance reduction. In spite of a lasting blood pressure reduction after treatment with diuretics, the structural hypertensive vascular changes do not seem to be influenced.

Old antihypertensive agents-diuretics and beta-blockers: do we know how and in whom they lower blood pressure?

Morbidity and mortality data that increasingly favor the use of diuretics and beta-blockers continue to accumulate. Nonetheless, the use of these agents particularly diuretics is viewed as a dated practice. The issue of which antihypertensive drug to use will remain complex and confusing as the marketing juggernauts of the pharmaceutical industry vigorously promote drug classes such as angiotensin- converting enzyme inhibitors, angiotensin-receptor antagonists, and calcium-channel blockers. A pharmacologic middle ground will probably be reached in the form of fixed-dose combination therapy. Diuretics and b-blockers are mechanistically rational when combined with numerous other drugs; thus, the issue of which drug should be used to begin treatment will be settled by a truce, albeit an uneasy one, favoring the increased use of fixed-dose combination antihypertensive therapy.

Beta blockers in hypertension

Beta-adrenoceptor antagonists are effective in the management of patients with mild-to-moderate hypertension. Noncardioselective agents, cardioselective agents and beta blockers with intrinsic sympathomimetic activity (ISA) are equally effective, provided they are used in equipotent doses. Beta blockers can be used as first-line therapy in the management of hypertension and can be safely combined with diuretics, vasodilators, or both, for a better control of blood pressure. The exact mechanism by which beta blockers decrease blood pressure remains speculative, but they all reduce cardiac output during long-term therapy; drugs with ISA lower cardiac output and heart rate less than do drugs without ISA. Pharmacokinetic properties of beta blockers differ widely; drugs metabolized by the liver have shorter plasma half-lives than drugs primarily excreted by the kidneys. Although many of the side effects of various beta blockers are similar, differences in water and lipid solubility account for a higher incidence of central nervous system side effects with lipid-soluble drugs (such as propranolol and metoprolol) than with hydrophilic drugs (such as atenolol and timolol). The incidence of cold extremities has been reported to be less with drugs with ISA, and the incidence of bronchospasm less with cardioselective drugs. In the management of uncomplicated mild-to-moderate hypertension, all beta blockers are equally effective and produce less troublesome side effects than alternative antihypertensive agents. For effective therapy beta blockers can be used in 2 divided daily doses or even once daily.(ABSTRACT TRUNCATED AT 250 WORDS)

How intrinsic sympathomimetic activity modulates the haemodynamic responses to beta-adrenoceptor antagonists. A clue to the nature of their antihypertensive mechanism

1 A survey has been made of the literature on acute and long-term haemodynamic effects of ten different β-adrenoceptor antagonists.

The β-adrenoceptor blockers are: pindolol, practolol, alprenolol, oxprenolol, acebutolol, penbutolol, metoprolol, atenolol, propranolol and timolol. The total numbers of patients included in this review are 396 patients in 41 acute studies and 410 patients in 36 long-term studies.

2 The effects of β-adrenoceptor blockers on the concentrations of plasma noradrenaline have also been reviewed. Ten studies including 110 patients on non-ISA-β-adrenoceptor blockers and eight studies including 116 patients on pindolol are presented.

3 In the acute studies (i.e. 15-90 min) arterial pressure was lowered by 1-7% and in the long-term studies (i.e. 3 days-5 years) by 6-17%.

4 The degree of cardio-depression induced by the various β-adrenoceptor blockers was inversely correlated with their pharmacologically defined quantity of intrinsic sympathomimetic activity (ISA) both in acute and in long-term studies.

5 In the acute studies the increments in peripheral vascular resistance were directly correlated with the degree of cardio-depression. This suggests that a fall in arterial pressure immediately after administration of a β-adrenoceptor blocker is prevented by increased vasoconstrictor nerve activity mediated through the arterial baroreflex.

6 The compensatory response of vascular resistance to cardio-depression was similar for β₁-selective and non-selective blockers, thereby indicating that extra-junctional vascular β-receptors are relatively unimportant for maintaining basal vascular tone.

7 In the long-term studies the correlation between changes in cardiac output and changes in vascular resistance was shifted to a lower level of vascular resistance. This means that the onset of blood pressure reduction during β-adrenoceptor blockade was associated with a fall in vascular resistance at any level of cardiac output. Thus vascular resistance was higher during treatment with a non-ISA-β-adrenoceptor blocker than during treatment with an ISA-β-adrenoceptor blocker.

8 The level of vascular resistance ultimately attained during treatment with the various β-adrenoceptor blockers appears to be inversely related to their effects on plasma renin activity.

9 The concentration of noradrenaline in plasma rose by approximately 30% during treatment with non-ISA-β-adrenoceptor blockers and fell by more than 30% after pindolol.

10 There is evidence that under propranolol, which reduces cardiac output and hepatic blood flow, the plasma noradrenaline clearance is diminished. Since noradrenaline is mainly cleared from the circulation by the lungs and by the liver, and since pindolol has no effect on cardiac output and hepatic blood flow, one may expect the plasma noradrenaline clearance not to be diminished by pindolol.

11 The reported effects of β-adrenoceptor blockers on plasma noradrenaline may indicate that the release of neurotransmitter is diminished, but in the case of non-ISA-β-adrenoceptor blockers this effect is not reflected by a decreased concentration of noradrenaline in plasma, because its clearance is also reduced.

12 The hypotensive effect of β-adrenoceptor blockers appears to be independent of blockade of postjunctional cardiac-β-receptors, juxtaglomerular-β-receptors and extrajunctional vascular β-receptors. This indicates that blockade of β-receptors at other sites (i.e. centrally and/or prejunctionally) is more important.

Merits of adding a beta blocker (acebutolol) to a diuretic (hydrochlorothiazide) in the treatment of hypertension

In a double-blind crossover study, the antihypertensive effect of hydrochlorothiazide alone and in combination with the beta blocker acebutolol was assessed in 18 patients suffering from mild to moderate hypertension. After a placebo period, the patients were placed on hydrochlorothiazide alone for four weeks at a dose of 50 mg daily. Acebutolol was than gradually titrated into the regimen until the optimum dose was established. The average dose was 555 mg per day, with the usual optimum dose 200 mg b.i.d. The patients then entered the crossover portion of the trial during which patients received either hydrocholorothiazide with acebutolol or hydrochlorothiazide with placebo. Each treatment period lasted six weeks. Blood pressure and heart rate were significantly lower with the combination treatment than with hydrochlorothiazide alone. At the end of each treatment period, the mean diastolic blood pressure (erect) was 90.5 mm Hg with hydrochlorothiazide-acebutolol but remained above 100 mm Hg with the diuretic alone. Neither hydrochlorothiazide nor acebutolol produced any significant changes in plasma renin activity or plasma aldosterone. There were very few side effects and no reports of bradycardia.

Fixed combination of sotalol and hydrochlorothiazide in the treatment of uncomplicated hypertension

The combination of sotalol and hydrochlorothiazide in a fixed ratio of 6.4:1 was evaluated in thirty patients with uncomplicated hypertension. In the first part of the study, once daily administration of an optimal dose of the combination was significantly more effective than either hydrochlorothiazide or sotalol alone in lowering both the supine and standing systolic and diastolic blood pressure. Blood pressure was still controlled 24 h after the previous dose. Serum potassium fell by 0.37 mEq/l from the mean pretreatment value after treatment with the combination, but it still remained within the normal range. In the second part of the study the long term effect of the combination on blood pressure, heart rate and biochemical parameters was studied in twenty patients. Supine and standing blood pressure fell by 28.7/15.3 mmHg and 29.5/17.6 mmHg, respectively (p less than 0.001). Serum potassium was 3.98 +/- 0.07 mEq/l after twelve months of therapy; potassium supplements were not administered. Like serum potassium, the other biochemical parameters remained within the normal range. The combination was well tolerated on long term use, and only one patient withdrew from the study.

Adaptation of hypertensives to treatment with cardioselective and non-selective beta-blockers. Absence of correlation between bradycardia and blood pressure control, and reduction in slope of the QT/RR relation

Thirty mild hypertensives were treated for more than two months with either cardioselective (atenolol or metoprolol) or non-selective (propranolol or pindolol) beta-blockers; the patients were assigned to the drugs in a double-blind manner. A procedure was designed to distinguish between the effects of the drugs themselves while treatment continued, and the development of adaptive changes which would persist when the drugs had been eliminated from the body. Though individual responses to treatment varied in both groups, the mean effect of the cardioselective and non-selective drugs in the control of hypertension was similar. There was no evidence of the development of supersensitivity or "rebound". On the contrary, an adaptive bradycardia (that is a fall of not less than 10% in heart rate persisting 52 hours after stopping treatment) was observed at rest in 17/30 patients, and peak heart rates and blood pressures during exercise were lower in both groups than before treatment. Cardioselective drugs induced a significantly greater bradycardia at rest than non-selective, but on exercise increases in heart rate were reduced more by the non-selective drugs, so that the same peak heart rates were reached on exercise in both groups. Adaptation also affected QT. The results suggest that two factors govern the shortening of QT by increases in heart rate, a "metabolic" effect, determined by sympathetic drive, and a "biophysical" effect determined by heart rate. The adrenergic effect is attenuated by acute beta-blockade, or by adaptation to prolonged blockade, leaving a shallow, rate-determined, slope to the QT/RR regression.

Angiotensin II blockade during combined thiazide-beta-blocker treatment

Sixteen patients (11 M, 5 F), median age 41 years, with essential hypertension insufficiently controlled on hydrochlorothiazide 75 mg/day (DBP greater than or equal to 100 mmHg) were investigated. Plasma renin concentration (PRC), angiotensin II concentration (PA II), aldosterone concentration (PAC), plasma noradrenaline concentration (PNAC), plasma volume (PV) and exchangeable sodium (NaE) were determined and a saralasin-infusion (5.4 nmol/kg/min) was carried out while the patients were on thiazide alone, and in fourteen cases, repeated 3 months later after addition of a beta-blocker (propranolol 6, metoprolol 6 and atenolol 2 patients). On thiazide alone PRC, PA II and PAC was higher than normal in the group as a whole and the angiotensin II-inhibitor, saralasin, caused a significant decrease in MAP in twelve out of sixteen patients. After addition of a beta-blocker SBP and DBP decreased from 164/109 mmHg to 136/94 mmHg. PRC and PA II decreased by 40% and 58%, respectively. At this point saralasin caused no significant change in MAP. No close correlation was found between changes in BP on beta-blocker treatment and either PRC, PA II or saralasin response on thiazide treatment. PV, NaE, PAC and PNAC did not change sigificantly. It is concluded that in pts with thiazide-induced stimulation of the renin-angiotensin system (RAS) addition of a beta-blocker leads to suppression of RAS and the angiotensin II dependence of the blood pressure is nearly abolished. This mechanism might well contribute to the antihypertensive effect of beta-blockade in this particular situation. However, the pharmacological changes induced by beta-blockade are very complex, and most likely other factors are involved in the antihypertensive effect of beta-blocking drugs.

Hydralazine and oxprenolol in the treatment of hypertension and the effect of these drugs on plasma renin activity

The effect of a vasodilator (hydralazine), a beta-blocker (oxprenolol) and also their combination, on essential arterial hypertension and plasma renin activity (PRA), was studied. Eighteen patients with mild hypertension (WHO I or II) were treated for 4 weeks with oxprenolol, hydralazine and their combination, with 4-week placebo periods between the active treatment periods. Oxprenolol and hydralazine lowered the blood pressure to a similar degree and their combination accentuated this effect. PRA decreased significantly on both the oxprenolol and the combination therapy, but increased during the following placebo and hydralazine periods to a level slightly higher than the initial level. Another group of eleven patients were treated with oxprenolol for 20 weeks. Blood pressure decreased almost to a normotensive level during the first 4 weeks of treatment and a little lower during the following 4 weeks. It remained at this level until the end of the trial. PRA decreased significantly during the first 4 weeks on oxprenolol and remained low during the whole 20-week treatment period. No correlation was found between the change in blood pressure caused by oxprenolol treatment and the initial placebo value of PRA, or, the change in PRA on oxprenolol treatment. These results support the view that the level of PRA has no significance when an antihypertensive treatment is being selected, e.g. beta-blockers.

The abrupt discontinuation of antihypertensive treatment

Although deleterious events following abrupt withdrawal of antihypertensive treatment are relatively uncommon, considerable attention has recently been focused on this problem. A withdrawal syndrome may occur after termination of almost all types of antihypertensive drugs, but most experience has been with the centrally acting agents and with beta-adrenoreceptor blockers. Abrupt discontinuation of high doses of centrally acting drugs such as alpha-methyldopa, clonidine, and guanabenz can produce a syndrome of sympathetic overactivity that includes agitation, headache, sweating, and nausea and less commonly can provoke rapid upswings in blood pressure. If beta blockers are suddenly stopped, a similar pattern can occur that may be related to excessive activity of thyroid hormones as well as sympathetic factors. Additionally, patients with ischemic heart disease may be susceptible to an acute exacerbation of their cardiac disease when beta-blocker treatment is stopped. It seems likely that discontinuation events can be particularly severe when combinations of different types of antihypertensive medications are sud-disease when betablocker treatment is denly stopped. This problem can be dealt with by educating patients to avoid sudden drug cessation and when elective discontinuation is planned, by gradual dose reduction.

Bioavailability and disposition of metoprolol and hydrochlorothiazide combined in one tablet and of separate doses of hydrochlorothiazide

1. The plasma levels and the urinary excretion of hydrochlorothiazide (HCT) have been studied after administration of single doses of 12.5 and 25 mg of the drug in solution and in combination with 100 mg of the selective beta 1-adrenoreceptor antagonist metoprolol in a rapidly dissolving tablet. 2. Metoprolol did not significantly influence the bioavailability or the time-course of HCT. 3. HCT had no significant effect on the time-course or the plasma levels of metoprolol. The average half-life, 4.4 +/- 0.9 h, is about the same as previously observed for separate doses of this drug. 4. It seems unlikely that repeated doses of the combination product studied will lead to biopharmaceutic or pharmacokinetic interactions of clinical importance.

Effect of nadolol in treatment of hypertension

Nadolol, a new beta-adrenergic blocking agent, was administered orally in gradually increasing single daily doses to 13 hospitalized patients with essential hypertension. Maximal doses ranged from 200 to 480 mg/day. Blood pressure was reduced in nine patients and heart rate was decreased in 11 patients. The decrease in blood pressure was either partial or temporary in five of the nine patients who responded. Concomitant administration of the diuretic chlorthalidone decreased blood pressure in a previously unresponsive patient. Nadolol effectively inhibited isoproterenol-induced tachycardia and decreased cardiac output by 18 per cent. Plasma renin activity and plasma aldosterone concentration were not changed significantly by the treatment. Body weight was not altered significantly. Blood pressure response was independent of the pretreatment renin levels or the change in renin induced by nadolol; it was also independent of the changes in cardiac output and heart rate but was more pronounced in patients with milder baseline hypertension. The decline in serum concentration of nadolol was consistent with the drug's reported half-life of 12.2 hours. The results indicate that single daily doses of nadolol alone can reduce blood pressure significantly with minimal cardiodepressant effects and no important side effects. The effectiveness of nadolol may be enhanced by the addition of a diuretic.

Double-blind comparison of metoprolol, alprenolol, and oxprenolol in hypertension

A double-blind comparison of the beta-blockers metoprolol, alprenolol and oxprenolol was carried out to evaluate their antihypertensive effect and tolerability. 105 patients with previously untreated hypertension entered the trial and 72 completed it. Side-effects were infrequent and were never the reason for drop-out. All three drugs caused a statistically significant reduction in blood-pressure at the lower of the two doses used during a dose-finding period. At the higher dose employed in this period, metoprolol caused a significantly greater reduction in diastolic blood-pressure than did alprenolol or oxprenolol. All three drugs caused a significant reduction in heart rate. During the following period, the beta-blockers were supplemented if necessary with hydrochlorothiazide. This was required less frequently in the metoprolol group than in the other two groups.

Placebo-controlled, double-blind clinical trial of alprenolol in African hypertensive patients

A placebo-controlled, double-blind clinical trial of alprenolol was carried out in 20 hypertensive Africans. The active drug and placebo were each administered for 8 weeks using a crossover design. Alprenolol was given in the form of a slow-release tablet preparation at a dosage of 200 mg twice daily. Four patients were withdrawn from the study either because of side-effects (2 patients) or non-compliance (2 patients). The mean reduction in blood pressure obtained in the 16 patients who completed the trial was less than that usually reported in Caucasians.

The second Lilly Prize Lecture, University of Newcastle, July 1977. beta-Adrenergic receptor blockade in hypertension, past, present and future

All beta-adrenoceptor blocking drugs that have been described share the common property of being competitive inhibitors. They differ in their associated properties, the presence or absence of cardioselectivity, membrane stabilizing activity, and partial agonist activity. Recently some beta-adrenoceptor blocking drugs have been reported which also possess alpha-adrenoceptor blocking activity. The associated properties have been used as a basis for classifying beta-adrenoceptor blocking drugs (Fitzgerald, 1969, 1972). The presence or absence of cardioselectivity is most useful for dividing beta-adrenoceptor blocking drugs. The non-selective drugs (Division I) can be further divided according to the presence or absence of intrinsic sympathomimetic activity (ISA) and membrane stabilizing activity (Fitzgerald's groups I-IV). Group I possess both membrane activity and ISA, e.g. alprenolol, oxprenolol, group II just membrane action, e.g. propanolol, group III ISA but no membrane action, e.g. pindolol. Fitzgerald placed pindolol in group I but should be placed in group III as it possesses a high degree of beta-adrenoceptor blocking potency in relation to its membrane activity (Prichard, 1974). Finally drugs in group IV have neither ISA nor membrane action, e.g. sotalol, timolol. The cardioselective drugs (Division II) can be similarly sub-divided into groups I-IV according to the presence or absence of ISA or membrane action (Fitzgerald grouped all these together as group V). Lastly there are new beta-adrenergic receptor blocking drugs which in addition have alpha- adrenergic receptor blocking properties (Division III).

The sympathetic system in hypertension

Several experimental observations accumulated during recent years have suggested an active participation of the sympathetic system in the pathogenesis and maintenance of hypertension in various experimental models of hypertension. The evaluation of sympathetic tone by various indirect means in human hypertension has also revealed that the sympathetic system plays an important role in the maintenance of hypertension in a subgroup of the human hypertensive population. The study of circulating catecholamines, which appears to be the best and most reliable indirect means to evaluate the sympathetic activity in the human, at present, has indicated that 25 to 40 per cent of patients with essential hypertension are characterized by higher basal circulating catecholamines and by a higher sympathetic reactivity in response to postural changes. These hyperadrenergic patients are also characterized by a higher heart rate, heart contractility, cardiac index and probably by higher plasma renin activity. The identification of these patients as a separate entity is desirable since it is possible that the evolution of the hypertensive disease and the response to therapy differ in this group of patients. The study of these patients could lead to a better understanding of the mechanisms underlying the pathogenesis of cardiovascular complications and to the development of more rational and efficient therapeutic approaches.

Plasma renin concentration in essential hypertension during beta-adrenergic blockade and vasodilator therapy

Plasma renin concentration (PRC) was measured in 46 patients with essential hypertension before and after treatment for 4 weeks with alprenolol 600-1200 mg daily. In 27 of these patients PRC was measured after 4 weeks of combined treatment with alprenolol and hydralizine. During alprenolol treatment PRC and blood pressure were reduced, but the changes were not correlated. Alprenolol treatment caused similar blood pressure reductions in patients with high and low PRC, and the antihypertensive efficacy of beta-adrenergic blocking agents could not be predicted from the pretreatment PRC. When beta-adrenergic blockade was supplemented with hydralazine, blood pressure was further reduced, but PRC remained unchanged. Although a causal relationship between blood pressure reduction and suppression of renin, production might exist at low doses of beta-adrenergic blocking agents, the present study did not indicate such a relationship when higher doses were used. It was shown that alprenolol inhibited the increase in PRC usually induced by hydralazine, but it is not known whether this was important for the effectiveness of the fall in blood pressure produced by hydralazine.

The effect of beta-adrenergic blockade on patterns of urinary sodium excretion, blood pressure and plasma renin activity in patients with essential and renovascular hypertension

The effects of beta-adrenergic blockade, using oxprenolol, were studied in plasma renin activity, urinary sodium excretion and blood pressure in ten normal subjects and in 120 patients with essential and renovascular hypertension. Blood pressure was reduced by oxprenolol administration. The hypotensive action of the drug was independent of either the basal plasma renin activity or of the plasma renin activity response. Oxprenolol decreased plasma renin activity in normal subjects and in patients with essential hypertension with normal or high basal plasma renin activity. Patients with low plasma renin activity may show a lack of response to the beta-blockade. In patients with renovascular disease the response of plasma renin activity to oxprenolol was not a discriminant factor between patients cured or not cured by surgery. Some renovascular patients were unresponsive to beta-blockade with oxprenolol.

The effect of pindolol on plasma renin activity in patients with essential hypertension

Twenty-two patients with essential hypertension were treated for 3 months with pindolol, and blood pressure and plasma renin activity were measured at rest and after stimulation (upright posture stimulation and insulin induced hypoglycaemia stimulation). Beta-receptor blockade produced a significant decrease in systolic and diastolic blood pressure. After treatment with pindolol the plasma renin activity was significantly lower. Under conditions of renin stimulation such as orthostasis and insulin produced hypoglycaemia, plasma renin activity was significantly lower in treated patients. There was no correlation between the fall of plasma renin activity and the decrease of blood pressure. Renin suppression is probably only one of the factors involved in the reduction in the blood pressure in these patients.

Effect of a new beta-adrenergic blocker, l-bunolol, on blood pressure and on the renin-aldosterone system

The antihypertensive effect of a new beta-adrenergic receptor blocker, l-bunolol, was evaluated in 11 hospitalized hypertensive patients of whom four belonged to the high-renin, five to the normal-renin, and two to the low-renin subgroup. There was a significant decrease in blood pressure in most patients, often to normal. Moreover, plasma renin levels were nearly always markedly suppressed, and this suppression preceded the fall in blood pressure. While most high and normal renin patients responded, the numbers of patients within each subgroup were too small to correlate the blood pressure responses with changes in renin levels. There was a significant induced decrease in aldosterone excretion, which usually paralleled the renin suppression. Pulse rate was also consistently reduced during treatment. No weight gain was observed, except in one patient who developed overt congestive cardiac failure. No other side effects were recorded. Ii is concluded that l-bunolol is another beta-blocking drug with significant antihypertensive action. It was found to be effective in cases that were resistant to propranolo. It is well tolerated and safe to use, provided that early evidence of fluid retention is sought for and treated immediately.

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.

Antihypertensive and renin angiotensin effects of metolazone with and without propranolol

Renin angiotensin system parameters and blood pressure (B.P.) were followed monthly in patients with essential hypertension on metolazone, 5 mg daily for three months and with added propranolol, 40 to 160 mg, for the subsequent three months. On metolazone alone at three months, sitting B.P. declined from 166/108 +/- 14/11 mm Hg to 145/98 +/- 14/9 mm Hg (P less than 0.005). Plasma renin activity (PRA) increased from 3.9 +/- ng/ml/hr to 10.4 +/- 8.6 ng/ml/hr (P less than 0.005); plasma angiotensinogen did not change. Venous blood angiotensin I and II levels (pg/ml) rose initially but returned toward control values. A significant decline in plasma renin substrate reactivity (PRSr) in index occurred. Propranolol addition caused further lowering of only systolic B.P. and predominantly in the standing position, more marked at one month (40 mg) than at three months (160 mg). No significant further changes were observed in any of the measured parameters of renin angiotensin system, except for a rise in PRSr index concomitant with B.P. elevation at three months. Metolazone-induced changes in B.P. showed significant correlations at three months with changes in PRSr index. It is concluded that during chronic metolazone administration, the overall activity of the renin angiotensin system was diminished or unchanged. Propranolol did not inhibit metolazone stimulated PRA but did cause further decline in B.P. in the first two months, unrelated to renin angiotensin system.