Beta-adrenergic blockade in diuretic-treated patients with essential hypertension

Renal Hemodynamic Changes after β-Blocker-Diuretic Combination Therapy in Azotemic Hypertensive Patients

The effects of β-blocker therapy with either nadolol or propranolol were compared during therapy with hydrochlorothiazide (HCTZ) 50 mg b.i.d. on glomerular filtration rate (GFR), effective renal plasma flow (ERPF), effective renal blood flow (ERBF), blood pressure, and heart rate in 22 patients with essential hypertension and mild to moderate renal insufficiency. The clearances of inulin and para-aminohippurate (PAH) were used to estimate renal hemodynamic measurements. These parameters were determined after 2 weeks of HCTZ plus placebo and at 1, 3, and 6 months after the addition of β-blocker to HCTZ. Significant reductions in blood pressure and heart rate were seen, but no significant reduction of renal hemodynamics were seen with either β-blocker-HCTZ combination. Since 50% of the patients in each drug group were either Black or White, hemodynamic data were also analyzed by race. One month after β-blocker addition there was a slight reduction of GFR in both Whites (47 ± 6 vs. 40 ± 5 ml/min, p > .05) and Blacks (44 ± 5 vs. 40 ± 6 ml/min, p < .05). By month 6, GFR in Whites rose to 57 ± 9 ml/min, whereas in Blacks it fell significantly to 36 ± 6 ml/min (p < .01). Similarly, at month 1, ERBF declined by 12% and 13% in Whites and Blacks, respectively. However, at month 6, ERBF rose by 28% in Whites and remained 11% lower in Blacks, p< .05. In summary, in the group as a whole neither β-blocker significantly altered renal hemodynamics when added to HCTZ therapy. However, after six months of combined therapy, Whites had elevations whereas Blacks had reductions of GFR and ERBF. These results suggest that the addition of β-blocker to diuretic therapy may be detrimental to certain hypertensive patients with limited renal reserve accelerating their need for a renal replacement therapy.

Body fluid volumes and the response of renin and aldosterone to short- and long-term thiazide therapy of essential hypertension

Plasma volume (PV), extracellular fluid volume (ECV) serum electrolytes, renin and aldosterone were measured before and after 1 week and 4 months of hydrochlorothiazide (HCT) treatment, 50 mg twice daily, in nine male patients with uncomplicated essential hypertension. All studies were carried out under strictly standardized conditions in a metabolic ward. After 1 week of HCT treatment, significant reductions were found in PV and ECV, but after 4 months only ECV was significantly reduced. During HCT therapy, renin and aldosterone were permanently elevated whereas serum sodium and potassium were lowered. After 1 week, renin was inversely correlated with PV and ECV and directly correlated with heart rate. After 4 months, renin was inversely correlated with serum sodium. These results indicate a permanent decrease in ECV during long-term HCT therapy. It is further suggested that the mechanisms responsible for the renin response during short- and long-term HCT treatment are different, changes in body fluid volumes and increased neural activity being responsible for the initial rise in renin, and serum sodium being the predominant factor during chronic treatment.

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.

Plasma renin activity and blood pressure during long term treatment with propranolol and diuretic

19 primary hypertensive patients were treated in random succession with diuretic, propranolol and the combination of both. It was found that the diuretic gave a sustained increase in plasma renin activity (PRA). There was a negative correlation between PRA level attained and blood pressure reduction. Propranolol treatment gave a sustained reduction of PRA. There was no correlation between PRA reduction and blood pressure reduction. When diuretic was combined with propranolol, PRA was in average at control level, and there was no correlation between the PRA reduction from diuretic value to combination value and the corresponding additional blood pressure fall. It is concluded that propranolol treatment does not transform patients to "low renin hypertensives" specifically sensitive to diuretic treatment.

Sympathetic overactivity in patients with chronic renal failure

BACKGROUND

Hypertension is a frequent complication of chronic renal failure, but its causes are not fully understood. There is indirect evidence that increased activity of the sympathetic nervous system might contribute to hypertension in patients with end-stage renal disease, but sympathetic-nerve discharge has not been measured directly in patients or animals with chronic renal failure.

METHODS

We recorded the rate of postganglionic sympathetic-nerve discharge to the blood vessels in skeletal muscle by means of microelectrodes inserted into the peroneal nerve in 18 patients with native kidneys who were undergoing long-term treatment with hemodialysis (of whom 14 had hypertension), 5 patients receiving hemodialysis who had undergone bilateral nephrectomy (of whom 1 had hypertension), and 11 normal subjects. RESULTS. The mean (+/- SE) rate of sympathetic-nerve discharge was 2.5 times higher in the patients receiving hemodialysis who had not undergone nephrectomy than in the normal subjects (58 +/- 3 vs. 23 +/- 3 bursts per minute, P < 0.01). In contrast, the rate of sympathetic-nerve discharge was similar in the patients receiving hemodialysis who had undergone bilateral nephrectomy (21 +/- 6 bursts per minute) and the normal subjects. The rate of sympathetic-nerve discharge in the patients receiving hemodialysis who had not undergone nephrectomy was also significantly higher (P < 0.01) than that in the patients with bilateral nephrectomy, and it was accompanied in the former group by higher values for vascular resistance in the calf (45 +/- 4 vs. 22 +/- 4 units, P < 0.05) and mean arterial pressure (106 +/- 4 vs. 76 +/- 14 mm Hg, P < 0.05). The rate of sympathetic-nerve discharge was not correlated with either plasma norepinephrine concentrations or plasma renin activity.

CONCLUSIONS

Chronic renal failure may be accompanied by reversible sympathetic activation, which appears to be mediated by an afferent signal arising in the failing kidneys.

Altered energy coupling in rat heart mitochondria following in vivo treatment with propranolol

Effects of acute and chronic treatment with propranolol on oxidative phosphorylation in rat heart mitochondria were examined. Acute propranolol treatment resulted in inhibition of coupled respiration with pyruvate + malate and succinate as substrates. Chronic treatment resulted in decreased state 3 respiration rates with all the substrates employed. The net effect of propranolol treatment was decreased ATP-phosphorylation rates suggesting that this was possibly one of the modes of its cardiodepressant activity. Additionally, chronic propranolol treatment brought about a decrease in the content of cytochrome c + c1 in heart mitochondria. Estimation of propranolol concentrations in serum, whole tissue homogenate and heart mitochondria indicated that although the mitochondria accumulated the highest amount of the drug, the intramitochondrial concentration of the drug was one or two orders of magnitude lower than that which is required to bring about inhibition of respiration under in vitro conditions. Besides, the concentrations reached under acute and chronic treatment conditions were almost comparable. The results, therefore, suggest that the action of the drug in vivo may involve more intricate mechanisms than those observed under in vitro conditions.

Renal hemodynamics and pharmacokinetics of bevantolol in patients with impaired renal function

The effects of bevantolol on renal blood flow and glomerular filtration rate and the drug's pharmacokinetics were studied for 7 days in 18 patients (mean age 50 years) with varying degrees of renal dysfunction. Patients were divided into 3 groups: group 1 had a creatinine clearance of 50 to 80 ml/min, group 2, 20 to 49 ml/min and group 3, less than 20 ml/min. After baseline inulin and paraaminohippuric acid clearance values were obtained, patients were given a single, 150-mg "priming" administration of bevantolol. The kinetics of the drug (including plasma drug levels, plasma half-life and plasma clearance) and its effects on renal function were observed for 24 hours. On days 4 to 6 of the study, patients received 150 mg of bevantolol twice daily, with only a single dose given on day 7. Bevantolol did not significantly affect either inulin or paraaminohippuric acid clearance in patients with differing degrees of renal function. In 50% of patients with a creatinine clearance of less than or equal to 50 ml/min, both the half-life and maximum trough serum levels were higher than the ranges seen in healthy subjects. However, neither value appears to be clinically relevant because bevantolol has a wide therapeutic range. Renal impairment did not change the percentages of the bevantolol dosage excreted unchanged or as conjugated drug in the urine, and no toxic or active drug metabolites accumulated in the blood. From these results, it appears that bevantolol may be used safely in short-term therapy of patients with renal impairment.

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)

Time course of development of the antihypertensive effect of propranolol

Ten patients with essential hypertension were hospitalized and treated with placebo, followed by their usual dose of propranolol. Systolic and diastolic blood pressure decreased significantly after the first dose of propranolol, and by the third day of propranolol treatment reached 84% to 92% of the maximum decrease achieved during the 6 days of treatment. Mean maximum falls in blood pressure were 13/12 mm Hg supine and 12/13 mm Hg standing. This development of the decrease in heart rate and blood pressure over 48 hours occurred in parallel with cumulation of propranolol to steady state in plasma. The decrease in diastolic, but not systolic, arterial pressure was directly related to pretreatment blood pressure, but not significantly related to pretreatment plasma renin activity (PRA) or change in PRA. Thus, single doses of propranolol lowered blood pressure in patients with essential hypertension, and with continued therapy, near maximum antihypertensive effects were achieved within 48 hours.

Serum sickness-like syndrome associated with propranolol therapy

A serum sickness-like syndrome developed in a 38-year-old woman with a history of drug allergy who had been taking propranolol hydrochloride (Inderal) for four days. The illness resolved after the drug was withdrawn and a course of prednisone therapy was given. We recommend caution to physicians in prescribing propranolol or other beta-adrenergic blocking agents for patients with a history of allergic reactions to drugs. Also, all patients using beta-blocking agents should be cautioned that although serum sickness-like syndrome is rare, it requires immediate medical attention.

Effects of clonidine on sympathetic function

Fifteen patients with essential hypertension and ten with pheochromocytoma were studied to assess the effect of clonidine, a centrally acting antihypertensive agent, on the functional and biochemical indices of sympathetic function. Single oral doses of clonidine (0.3 mg) decreased supine plasma norepinephrine significantly in essential hypertension, but not in pheochromocytoma despite producing similar reductions in blood pressure and heart rate. Plasma renin activity was unchanged in both groups. In untreated essential hypertension, head-up tilt increased diastolic blood pressure, heart rate, and plasma norepinephrine. Three hours after a single oral dose of clonidine, head-up tilt resulted in significant blood pressure reductions, although heart rate and plasma norepinephrine increased dramatically. Clonidine might reduce blood pressure by inhibiting sympathetic outflow, and any effect on plasma renin activity appears unimportant in its antihypertensive action. In pheochromocytoma clonidine decreases blood pressure without altering plasma norepinephrine, which is consistent with the concept that the norepinephrine released from axon terminals of sympathetic postganglionic neurons is biologically more significant than circulating catecholamines.

Systolic time intervals as possible predictors of pressure response to sustained beta-adrenergic blockade in arterial hypertension. A within-patient, placebo-controlled study

Systolic time intervals (STI) were recorded at rest and during isometric exercise (IHG) in 20 hypertensive outpatients, WHO Stage 1 or 2. In a double-blind crossover study, slow-release metoprolol 200 mg once daily and matched placebo were given for 4 weeks each, at the end of a 2-week placebo washout. Blood pressure and STI were taken in the last day of washout and of either crossover period. Treatment decreased blood pressure and heart rate values at rest and on peak IHG; it didn't modify preejection period index (PEPI), left ventricular ejection time index (LVETI), and their ratio at rest, but decreased the ratio between diastolic blood pressure and PEPI (DBP/PEPI ratio) at rest and on peak IHG and lengthened the PEPI at peak IHG. Resting PEPI values on placebo treatment showed a negative correlation with systolic (r = -0.72) as well as diastolic (r = -0.80) pressure reduction on slow-release metoprolol as compared with placebo treatment. The PEP/LVET ratio at rest on placebo treatment showed a negative correlation with systolic (r = -0.78) as well as diastolic (r = -0.82) pressure reduction at rest on metoprolol compared with placebo treatment. Patients with a resting PEP/LVET ratio less than 0.43 showed a reduction in both systolic and diastolic pressure approximating or exceeding 20 mm Hg, whereas patients with a PEP/LVET ratio greater than 0.47 showed a decrease in systolic and diastolic blood pressure of less than 10 mm Hg. In patients with a PEP/LVET ratio of 0.43 to 0.47 (50% of the trial population), STI didn't show any correlation with the pressure response to beta-blockade. A positive correlation was found between the DBP/PEPI ratio at rest on placebo treatment and systolic (r = 0.56) as well as diastolic (r = 0.76) pressure reduction at rest on slow-release metoprolol compared with placebo treatment. Thus, STI appeared as promising predictors of the magnitude of blood pressure response to sustained beta-blocking therapy in mild-to-moderate essential hypertension, mostly in patients with a resting PEP/LVET ratio less then 0.43 or greater then 0.47.

The effect of a combination of timolol, hydrochlorothiazide and amiloride on 24 hour blood pressure control using ambulatory intra-arterial monitoring

1 The effectiveness of fixed combination tablets of timolol 10 mg, hydrochlorothiazide 25 mg and amiloride 2.5 mg (Moducren) once daily in the control of blood pressure has been assessed in fully ambulant hypertensives by the technique of continuous intra-arterial recording. Highly significant blood pressure reduction (P less than 0.001) was obtained consistently throughout the whole day, confirming the potency and usefulness of the preparation for those patients who need more than one drug to control their blood pressure. 2 Blood pressure responses to both isometric and dynamic forms of exercise were also significantly lowered by combination therapy. 3 The addition of a diuretic to a beta-adrenoceptor blocker appears to be an advantage if the aim of treatment in hypertension is 24 h blood pressure control.

Pindolol and systolic time intervals in patients with hypertension

Two studies of systolic time intervals (STIs) in patients with mild to moderate hypertension (HBP) revealed that no mean change in systolic intervals occurred with pindolol therapy, although some patients had significant alterations in their STIs. Pindolol responders with normal pretreatment preejection period to left ventricular ejection time (PEP/LVET) ratios had a significant increase in this ratio following pindolol therapy, whereas those with abnormal pretreatment PEP/LVET ratios had improvement in this ratio on administration of the drug. Patients on propranolol showed no change in PEP/LVET ratio. Propranolol administration slowed heart rate and lengthened Q-S2, S1-S2, and LVET, however, without altering the Q-S2 and LVET index, indicating that the changes were caused by the effect of propranolol on the heart rate alone. Chlorthalidone in high doses significantly reduced the Q-S2 index and the S1-S2 index, indicating that these changes were not caused by alteration of the heart rate. The second study suggests that STIs may provide a predictive clue for clinical response to pindolol. Patients with normal cardiac function (group I) are more likely to respond to pindolol than are those with abnormal cardiac function (group II). Directionally opposite changes in STIs in the two subgroups suggest different mechanisms for changing cardiac function. Pindolol's dual role as a beta-blocking agent with intrinsic sympathomimetic activity is proposed as a possible explanation, beta-blocking effects predominating in group I and sympathomimetic activity balancing the beta effect in group II.

Responses of catecholamines and blood pressure to beta-blockade in diuretic-treated patients with essential hypertension

Twenty patients (mean age 49 +/- 4 (SEM) yr) with mild to moderate essential hypertension were studied during placebo conditions, following 6 weeks of chlorthalidone monotherapy and 6 to 28 weeks of combined beta-blocker-chlorthalidone treatment, or vice versa. Compared to chlorthalidone therapy alone, addition of a beta-blocker to this diuretic caused a further blood pressure reduction in 11 patients (Responders); in 9 patients addition of a beta-blocking agent failed to further reduce blood pressure (Non-responders). Supine and upright plasma renin, aldosterone, norepinephrine and epinephrine levels and catecholamine excretion rates were always comparable between Responders and Non-responders. In both groups plasma and urinary norepinephrine or epinephrine values were not significantly altered following addition of a beta-blocker; heart rate and plasma renin activity were decreased in both groups to a similar extent. It is concluded that the antihypertensive mechanism of beta-blockers given to diuretic treated patients with essential hypertension is independant of renin and not associated with changes in plasma or urinary catecholamines.

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.

Controlled comparison of the effects of furosemide and hydrochlorothiazide added to propranolol in the treatment of hypertension

Forty patients completed a double-blind parallel group study comparing furosemide (FUR) and hydrochlorothiazide (HCT) when added to a stable dose of beta blocker in the treatment of mild to moderate hypertension. Both diuretics caused a significant additional fall in blood pressure (BP) when added to propranolol, and there were no differences in the mean BP achieved. However, a higher proportion of patients achieved satisfactory control (BP less than 160/95 mm Hg) on FUR than on HCT and, in addition, there was a more marked dose-response effect with FUR. This study showed that FUR is at least as effective as HCT in the treatment of hypertension when added to propranolol, and appears to possess certain advantages in comparison to the thiazide.

The effect of renin and aldosterone inhibition by beta-adrenergic blockade on the response to the new diuretic azosemide

The effect of repeated Azosemide infusions (20 mg in 500 ml 5% glucose for one h) on urine volume and electrolyte excretion, and on the activity of the renin-angiotensin-aldosterone system (RAAS) was studied in a group of 15 patients with benign essential hypertension before and during treatment with the beta-adrenergic blocker Trimepranol. Azosemide alone had a marked but short-lasting diuretic and natriuretic effect. Repeated administration on three consecutive days led, however, to a progressive decrease in the natriuretic effectiveness of Azosemide, associated with an increase in plasma renin activity (from 0.413 o.032 to 1.631 0.438 pmol/l). Treatment with Trimepranol 20 mg/day enhanced and prolonged the diuretic and natriuretic response to Azosemide concomitantly with a reduction of its stimulatory effect of RAAS. There results suggest that stimulation of the RAAS might be responsible for the diminishing effectiveness of repeated Azosemide infusions and that the stimulation could be, at least partly, inhibited by a beta-blocker Trimepranol, resulting in a greater diuretic and natriuretic effect of Azosemide.

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.

Correlation between propranolol in plasma and urine, renin-aldosterone system and blood pressure in essential hypertension

Thirty patients with mild or moderate essential hypertension, and a fixed elevation of diastolic blood pressure, were randomly allocated to three groups and treated with propranolol 40 mg x 4 (Group 1), 80 mg x 4 (group 2) and 160 mg x 4 (Group 3). Blood pressure (BP), pulse rate (PR), plasma renin activity (PRA), plasma aldosterone concentration (PAC), total plasma propranolol (tPP), free plasma propranolol (fPP), and 24 h urinary propranolol excretion (UP) were determined at the end of four consecutive periods: (A) after four weeks without any treatment; (B) after two to three weeks during which the propranolol dose was gradually increased to the intended level; (C) after four weeks, and (D) after eight weeks of unchanged treatment. The maximum reduction in diastolic BP occurred after period B, and in systolic BP after Period C, for Groups 2 and 3, and for all groups together; for Group 1, however, the maximum diastolic BP reduction was first seen after period C. PR was reduced to the same level in all groups after period B. After period B, PRA an PAC fell in all groups, and remained reduced during C and D Group 1. After periods C and D, PRA and PAC in Groups 2 and 3 did not differ significantly from the levels after period A; tPP, fPP and UP were significantly correlated with the propranolol dose, and were lowest in Group 1 and highest in Group 3; UP was negatively correlated with systolic but not diastolic BP in Periods B, C and D. In contrast neither fPP nor tPP were correlated with systolic or diastolic BP. There was no significant correlation between PRA, PAC and changes in PRA or PAC on the one hand and tPP, fPP, UP, BP or changes in BP on the other. It was concluded that propranolol effectively reduced BP, but diastolic BP reduction was most rapidly obtained at 320 and 640 mg daily, that the activity of the renin -aldosterone system was initially suppressed in all group, but for unknown reasons it increased towards the control level after seven to eleven weeks of therapy with 320 and 640 mg/day, and that the reduction in systolic BP increased with higher doses of propranolol and with increasing urinary propranolol excretion.

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.

Recent pathogenic aspects in essential hypertension and hypertension associated with diabetes mellitus

The sympathetic system, the body sodium-fluid volume state, the renin-angiotensin system, functional and structural characteristics of the heart and blood vessels, and some other components are important complementary factors in blood pressure regulation. A deviation from the normal equilibrium among these components, with a persisting non-physiologic increase in pressor factor(s) or in the basal vascular tone and/or cardiovascular reactivity to pressor factors, leads to hypertension. This review discusses recent observations and concepts regarding the pathogenesis of essential hypertension and hypertension associated with diabetes mellitus. It focuses on the roles of various pressor factors as well as cardiovascular pressor responsiveness in the genesis of high blood pressure and in the antihypertensive mechanism of diuretic treatment.

Effect of beta-adrenoreceptor blockade on the renin response to acute natriuresis

1. The response of plasma renin activity to frusemide 40 mg given intravenously, was examined before and after oral propranolol 160 mg daily for 7 days in normal and hypertensive subjects. 2. Although basal renin levels were often reduced, the increase following frusemide was essentially unaltered by propranolol therapy. 3. These findings indicate that enhanced renin activity associated with diuretic use may not be prevented by concurrent propranolol administration. Limitation of hypotensive action of combined beta-blocker diuretic therapy can therefore be anticipated. 4. Preservation of the renin stimulatory effect of frusemide during beta blockade confirms the value of this procedure in the investigation of mineralocorticoid and renovascular hypertension were discontinuation of treatment may be undesirable.

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.

Effect of propranolol on the renin response to frusemide in man

The response of plasma renin activity (PRA) to frusemide, 40 mg given intravenously, was examined before and after oral propranolol 160 mg daily for seven days in normal and hypertensive subjects. Although basal PRA was reduced in many cases, the increase following frusemide was essentially unaltered by propranolol therapy. Evidence is presented that adequate beta adrenoceptor blockade was attained in these studies. Increasing the dose of propranolol to 240 mg daily for seven days in two subjects did not alter renin responsiveness to frusemide. Stimulation of renin release by oral frusemide, examined in one subject, was also unaltered by propranolol therapy. These findings indicate that enhancement of renin activity associated with diuretic use may not be prevented by concurrent propranolol administration. Limitation of the hypotensive action of combined beta blocker-diuretic therapy can therefore be expected. The fact that the renin stimulating effect of frusemide is preserved during beta blockade indicates that this procedure can be used in the investigation of hypertension even in those patients in whom discontinuation of beta blocking treatment may be undesirable.

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).

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.

Diuretic-induced renal impairment without volume depletion in cirrhosis: changes in the renin-angiotensin system and the effect of beta-adrenergic blockade

In 4 patients with cirrhosis and ascites, diuretic therapy resulted in an impairment of renal function that was associated with a rise in plasma renin activity (PRA). In 3, this occurred in the absence of volume depletion. When diuretics were discontinued, renal function returned to normal. beta-adrenergic blocking drugs were then given to suppress renin secretion and diuretics restarted. On this occasion, impairment of renal function did not occur. In 2 further patients, administration of beta-adrenergic blockers during a period of diuretic-induced renal impairment resulted in an improvement in renal function. Although these findings may indicate that diuretic-induced renal impairment in cirrhosis is at least partly due to activation of the renin-angiotensin system, in another group of patients a diuretic-induced rise in PRA was not associated with a deterioration in renal function.

Oxdralazine, a new peripheral vasodilator, combined with propranolol and hydrochlorothiazide: a rational approach to antihypertensive treatment

Forty-three patients suffering from hypertension of different origin (chronic renal failure, gout, or idiopathic) were treated with propranolol (121 +/- 12 mg q.d.) plus hydrochlorothiazide (50 mg q.d.) for 75 +/- 9 days. Blood pressure did not return to normal limits in 15 patients, who were continued on the same protocol plus 10 to 50 mg oxdralazine q.d. After an average of 68 +/- 35 days blood pressure fell from 180/110 mm Hg to 145/90 mm Hg without orthostatism, significant side effects, or changes in GFR. This combination seems particularly successful since propranolol will prevent the undesired rise in cardiac output due to oxdralazine as well as the activation of the renin-angiotensin axis due to diuretics. Thus, the antihypertensive properties of each agent will be enhanced by a reduction in side effects by the associated drug, resulting in optimal blood pressure control.

Individual factors influencing the response to a beta-adrenergic blocking agent given alone and in combination with a diuretic on arterial hypertension

103 patients with arterial hypertension were treated with timolol + placebo for 7 weeks in a multicentre trial, and with timolol + hydrochlorothiazide and amiloride for a further 7-week period. The decrease in blood pressure (BP) produced by timolol alone was influenced neither by the dose of timolol, initial heart rate, magnitude of pretreatment BP nor by age. 64% of the patients less than 40 years of ages, and 48% of the older patients, were well regulated on beta-blocker monotherapy. When the diuretic was given in addition, the BP response in the older age group improved, whereas younger patients showed no change. A significant correlation was found between age or magnitude of untreated BP and the decrease in BP caused by the diuretic. The cardiothoracic ratio increased significantly on timolol alone, whereas no change was found on the combined therapy. Weight changes in the two different treatment periods showed a significant correlation, but they were not related to the observed reduction in BP. The results suggest that in younger patients, beta-blocker therapy is just as effective as a combined treatment with a diuretic, whereas in older patients considerably better regulation is achieved by combined therapy.

Clinical pharmacologic observations on timolol. II. Antihypertensive effect and kinetic disposition on twice-daily dosing in patients with mild or moderate hypertension

Timolol given on a twice-daily schedule has shown both antihypertensive effectiveness and plasma renin-suppressing action in eight patients with mild or moderate hypertension. However, the causal relationship between the drug plasma level, blood pressure fall, and change in plasma renin activity was not so clearly demonstrated in the present study. The disposition profiles of timolol at the steady state show an elimination half-life of 4.7 +/- 0.7 hours and a total plasma clearance of 225 +/- 21 ml/min. These values are found to be different from those of our previous observations obtained in normal individuals. Although the range of mean timolol concentrations at steady state varies to a certain extent among different patients, the dosage regimens for patients who will receive treatment for certain chronic disease states (e.g., arrythmias, obstructive cardiomyopathy, and angina pectoris, but not hypertension) in relation to plasma levels should be based on the disposition data obtained under steady state conditions. Bronchospasm developed in one of eight patients whose timolol level was found to be higher than the average of other patients given the same dosage.

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).

Effect of timolol plus hydrochlorothiazide plus hydralazine on essential hypertension

The effect on hypertension of hydrochlorothiazide 100 mg daily plus timolol 20-60 mg daily versus hydrochlorothiazide plus placebo and of hydrochlorothiazide plus timolol plus hydralazine 40-200 mg daily versus hydrochlorothiazide plus placebo plus hydralazine was evaluated in a double-blind, randomized, crossover study in 38 patients with hypertension. Hydrochlorothiazide plus timolol was more effective than hydrochlorothiazide plus placebo in lowering both supine and standing systolic and diastolic blood pressures. Hydrochlorothiazide plus timolol plus hydralazine was a very effective regimen in lowering both supine and standing systolic and diastolic blood pressure. The patients tolerated this regimen well with greater hypotensive activity and a lower incidence of side effects than on hydrochlorothiazide plus placebo plus hydralazine.