Cardiovascular and metabolic profile during intervention with urapidil in humans

Urapidil, a dual-acting antihypertensive agent: Current usage considerations

Despite the availability of a wide range of effective blood pressure (BP)-lowering agents, a substantial proportion of patients with hypertension fail to achieve target BP levels. The majority of patients with hypertension need a combination of two or more drugs to achieve BP targets and choice of second-line or subsequent-line therapy is an important consideration in hypertension management. Alpha-1-adrenoreceptor antagonists (alpha-blockers) have a BP-lowering effect broadly similar to the other antihypertensive drug classes and are effective as add-on therapy in patients with inadequately controlled hypertension. Alpha-blockers may also have therapeutic benefits that go beyond BP control, including improvements in lipid profile and glucose metabolism, as well as reducing the symptoms of benign prostatic hyperplasia. Urapidil has an alpha-blocking effect but, unlike other alpha-blockers, also has a central sympatholytic effect mediated via stimulation of serotonin 5HT(1A) receptors in the central nervous system. Several studies have suggested that oral urapidil is effective and well tolerated when used as second-line therapy in patients with BP inadequately controlled with other agents. Urapidil has also been shown to improve glucose and lipid metabolism in hypertensive patients with concomitant diabetes and/or hyperlipidemia. Intravenous urapidil is effective in the treatment of hypertensive crises, perioperative hypertension, and pre-eclampsia and may have a potential role in the management of acute stroke. In this review, the use of alpha-blockers in hypertension is discussed, with particular focus on urapidil for the lowering of BP in a variety of clinical settings.

Renal haemodynamics and sodium excretory capacity during urapidil treatment in patients with essential hypertension

OBJECTIVE

Since renal sympathetic nerves are involved in the regulation of sodium excretion, we investigated whether treatment with urapidil, an alpha1-adrenoceptor blocking agent which also lowers sympathetic activity, alters sodium excretory capacity in patients with essential hypertension.

DESIGN

A double-blind, randomized, parallel-group study.

METHODS

Studies were carried out in 26 patients who were randomized to treatment with either placebo or urapidil for 8 weeks. Before and after treatment blood pressure, renal haemodynamics and various neurohormones were measured, as well as the response of these variables to a hypertonic saline infusion.

RESULTS

Urapidil had no effect on renal haemodynamics or neurohormones at rest However, as compared to placebo the saline-induced rises in renal plasma flow and glomerular filtration rate lasted longer during treatment with urapidil. Responses of renin, angiotensin II and catecholamines were not modified by urapidil. On the other hand, aldosterone was less suppressed while atrial natriuretic peptide was less stimulated following the saline load when patients had been treated with urapidil. Cumulative sodium excretion during a 3 h period from the moment of saline infusion was similar whether patients had been treated with placebo or with urapidil.

CONCLUSIONS

Our data show that urapidil interferes with renal haemodynamics after sodium loading but that any tendency to promote sodium output may be offset by changes in aldosterone and atrial natriuretic peptide. We conclude that urapidil, under the circumstances tested, does not affect the sodium excretory capacity of the kidney.

Increased pressor response to noradrenaline in pituitary dependent Cushing's syndrome

OBJECTIVES

The mechanism of hypertension in Cushing's syndrome remains undetermined. Some studies have demonstrated an increased sensitivity to pressor agents but it is not clear if patients with Cushing's syndrome of different aetiologies demonstrate this finding. We have examined pressor sensitivity in a group of patients with Cushing's disease (pituitary dependent hypercortisolism) by measuring blood pressure during incrementally increasing infusions of noradrenaline.

METHODS

Eight subjects (7 female, 1 male), aged 42.2 +/- 4.5 years (mean +/- SEM) with Cushing's disease were studied. Eight age- and sex-matched control subjects were also studied. Four of the eight controls and five patients with Cushing's disease had elevated blood pressure. All medication for this had been stopped at least seven days prior to the study. After subjects ate a light breakfast, ECG leads and a sphygmomanometer were attached, an intravenous cannula was inserted and all subjects then rested quietly for 60 minutes. Noradrenaline was then infused intravenously for 10-minute periods at concentrations of 0.01, 0.03, 0.07, 0.11 and 0.18 microg/kg/minute.

RESULTS

On the day of the study the baseline blood pressures and pulse rates in the patients with Cushing's disease (blood pressure; 138/87 +/- 6/3 mmHg, pulse 76.5 +/- 4.8 beats/minute) and controls (blood pressure; 126/86 +/- 6/6 mmHg, pulse 71.2 +/- 3.7 beats/minute) were not significantly different. The mean change in diastolic blood pressure from baseline at the time of the peak increase or when the test was stopped was 21. 5 +/- 4.7 mmHg in Cushing's disease compared to 7.0 +/- 2.5 mmHg in controls (P = 0.03). The mean change in mean arterial pressure from baseline at the time of the peak increase or when the test was stopped was 22.0 +/- 4.0 mmHg in Cushing's disease compared to 13.0 +/- 2.4 mmHg in controls (P = 0.03). No significant difference in mean change of systolic pressure (26.0 +/- 4.6 vs. 25 +/- 4.0 mmHg) or pulse rates (- 11.1 +/- 1.8 vs. - 4.7 +/- 2.6) was seen in the group with Cushing's disease as compared to the control group.

CONCLUSIONS

We conclude that patients with pituitary-dependent Cushing's syndrome have enhanced pressor diastolic and mean arterial responses to noradrenaline and this may be an important underlying mechanism for the hypertension seen in this particular group of Cushing's syndrome patients.

Urapidil treatment decreases plasma fibrinogen concentration in essential hypertension

The effects of antihypertensive drugs on cardiovascular metabolic risk factors were monitored in 42 patients with essential hypertension (diastolic blood pressure [DBP] >95 mm Hg). In a double-blind randomized parallel-group study, they were treated with atenolol 50 mg once per day (n = 25) or urapidil 60 mg twice per day (n = 17), a peripheral alpha1-receptor blocker with an additional central serotonin 1A (5HT1A) receptor agonistic effect, for 12 weeks. Plasma fibrinogen concentration decreased by 24% (P < .0001) during urapidil treatment and by 9% (P = .05) during atenolol treatment, with the effects of the two drugs differing significantly. Plasminogen activator inhibitor (PAI) activity tended to increase by 17% (nonsignificant [NS]) in the atenolol-treated group and to decrease by 4% (NS) in the urapidil group. Differences between the effects of the two drugs on very-low-density lipoprotein (VLDL) triglycerides (TG) and on total TG were significant. During urapidil medication, these two parameters were reduced by 22% and 13%, respectively, but the changes were nonsignificant (P = .11 and P = .14, respectively). In contrast, atenolol treatment caused a significant increase in both VLDL TG and total TG of 31% and 21%, respectively. Hemoglobin A1c (HbA1c) increased by 4% (P = .06) during atenolol treatment, but was unaffected by urapidil. There were no significant changes within or between atenolol- and urapidil-treated groups regarding glucose disposal on an oral glucose tolerance test (OGTT) or the insulin sensitivity index on a hyperinsulinemic-euglycemic clamp test. In conclusion, urapidil treatment was characterized by neutral or favorable effects on several variables associated with the metabolic syndrome. Atenolol treatment had neutral properties in some metabolic aspects, but deleterious effects on lipid status.

The effect of urapidil on responses to phenylephrine, angiotensin and isoprenaline in man

Intravenous urapidil, 40 mg bolus followed by an infusion of 18 mg.h-1 for 2 h was administered to 6 female non-patient volunteers. Randomised cumulative dose response curves to angiotensin, phenylephrine and isoprenaline were performed before and commencing 30 min after the start of the infusion of urapidil. Urapidil significantly reduced supine systolic blood pressure, 118.5 mm Hg to 105.3. The diastolic blood pressure was not significantly reduced, heart rate was not affected. Urapidil did not affect the responses to angiotensin or isoprenaline. Urapidil inhibited the pressor response to phenylephrine. The dose required to increase systolic blood pressure by 20 mm Hg increased from 156.9 micrograms.min-1 before to 685 micrograms.min-1 during urapidil; Dose ratio from individual values of 4.58. Urapidil concentrations were not significantly different before and after each agonist infusion. It is concluded that urapidil has alpha 1-adrenoceptor blocking activity in man without any non specific vasodilator action and that it is devoid of beta adrenoceptor blocking action.

Urapidil, a multiple-action alpha-blocking drug

Investigations in animals indicate that urapidil has a number of actions that may be relevant to its antihypertensive effect. It has an alpha 1-blocking action, a weak beta 1-blocking effect, an interaction with a serotonin receptor and a central depression of sympathetic tone. Urapidil is well absorbed orally with a bioavailability of about 70% and a time to peak concentration of about 4 hours after a sustained release capsule. It is metabolized in the liver at a half-life of 4.7 hours. Peripheral alpha 1-blocking activity has been demonstrated in humans. A shift to the right in the dose-response curve to phenylephrine has been found after urapidil, whereas responses to angiotensin are not affected. Evidence for beta 1-blocking activity is marginal. Urapidil does not inhibit the exercise increase in heart rate. Some investigators have suggested a possible inhibition of isoprenaline tachycardia; others have found no evidence. There is some evidence suggestive of a central action of urapidil in humans as lower single doses result in a decrease in blood pressure and an increase in heart rate. With higher doses the hypotensive effect continues but the tachycardia no longer occurs. However, urapidil has been reported to increase noradrenaline levels, although there has been a report with a high dose reducing vanillylmandelic acid excretion. Evidence for changes in renin is inconsistent. Hemodynamic studies have revealed findings that are compatible with peripheral alpha 1 blockade. After intravenous administration, peripheral resistance is reduced along with arterial pressure, and cardiac output is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenetic and therapeutic relevance of cardiovascular pressor reactivity to norepinephrine in human hypertension

In normotensive humans with a positive family history of essential hypertension, blood pressure (BP) is often dysregulated. Body sodium, blood volume, plasma angiotensin II (AngII), epinephrine and norepinephrine (NE), their responses to changes in sodium intake or posture, as well as baroreflex function, beta-receptor-mediated cardiac responsiveness, and the responsiveness of BP to AngII appear to be largely unaltered. However, the responsiveness of BP to NE is commonly exaggerated. An increase in potassium intake may improve the NE hyperreactivity and concomitantly lower BP within the "normotensive" range. Therefore, a selective vascular NE hyperreactivity relative to existing sympathetic activity seems to be a common familial abnormality predisposing for the development of essential hypertension. In borderline or established essential hypertension, an inappropriate vascular reactivity relative to sympathetic activity probably complements other mechanisms contributing to the maintenance of hypertension. Various antihypertensive treatments may lower BP at least in part by improving cardiovascular NE (hyper)reactivity without provoking an equivalent rise in sympathetic activity. These include dietary potassium supplementation, thiazide-type agents, indapamide, calcium channel blockers, postsynaptic alpha 1-blockers, and AngII converting enzyme inhibitors.

Yohimbine and aldosterone responsiveness to angiotensin II or corticotrophin in normal subjects

In normal man the sympathetic nervous system exerts an inhibitory influence on aldosterone responsiveness to angiotensin II. The possible role of alpha-2 adrenoceptors was assessed by studying the changes of plasma aldosterone during an angiotensin II infusion at the dose of 1, 2, 5 and 10 ng/kg. min or after corticotrophin infusion, 0.25 mg, in 8 normal subjects before and after treatment with the selective alpha-2 adrenoceptor antagonist, yohimbine, at a maximal dosage of 60 mg daily. Yohimbine did not modify blood pressure, body weight, the supine levels of angiotensin II, renin and aldosterone, the pressor response to angiotensin II and the correlation relating plasma aldosterone to plasma angiotensin II obtained during infusion studies. These findings suggest that the inhibitory influence of the sympathetic nervous system on aldosterone responsiveness to angiotensin II.

Stimulation of renin secretion by potassium-channel activation with cromakalim

The cardiovascular and endocrine profile of cromakalim has been studied in 8 healthy men (age 25 +/- 2 years: means SEM) and its influence on renin release from cultured rat juxtaglomerular cells in vitro has also been examined. According to a double-blind, randomized sequence the subjects received placebo or cromakalim 1 mg as a single daily oral dose for 5 days. Compared to placebo, cromakalim significantly increased plasma renin activity (+ 122%; from 1.73 to 3.87 ng AI.ml-1.h-1), angiotensin II (+ 105%; from 5.1 to 10.5 pg.ml-1), and norepinephrine (+ 61%) levels, and heart rate (+ 8%). Plasma aldosterone, blood pressure and indices of the electrolyte-fluid volume state were unchanged. Cromakalim in vitro stimulated renin release, from 9.9 to 36.5 ng AI.h-1.30 min.mg cell protein, from juxtaglomerular cells. It appears that the presumed K+-channel activator cromakalim increases renin release in vivo at least in part by direct stimulation of renal juxtaglomerular cells.

Urapidil in the treatment of hypertension

Urapidil is an alpha 1-adrenoceptor antagonist which also has a central antihypertensive effect, the mechanism of which has yet to be conclusively defined. A number of open and comparative studies have produced evidence for the efficacy and safety of urapidil. A study recently completed by the author produced a dose-dependent antihypertensive effect of urapidil which, however, failed to achieve statistical significance, probably due to a large variance of the data and an unexpectedly large placebo effect. Adverse reactions are those expected from an alpha 1-blocker, particularly dizziness, as well as nausea and fatigue. Urapidil is potentially an important new antihypertensive agent; further variable dose and combination (with other antihypertensive agents) studies would help further define its therapeutic niche.

Acute haemodynamic effects of urapidil in patients with chronic left ventricular failure

Urapidil, a new alpha 1-adrenoceptor blocking drug, has been shown to be effective in the treatment of hypertension. Ten normotensive patients with severe congestive heart failure were given Urapidil 25 mg i.v. twice in 15 min and the haemodynamic effects were measured. There was a significant fall in systolic blood pressure (-16%), mean blood pressure (-13%), left ventricular end-diastolic pressure (-38%), mean pulmonary artery pressure (-31%) and wedge pressure (-40%). Total peripheral resistance fell by 25%, whereas pulmonary arteriolar resistance did not change significantly. Cardiac output increased by 22%. The increase in cardiac output with decreasing peripheral resistance and LV pressures suggests that urapidil may be useful in the therapy of congestive heart failure.

Age, race, diagnosis, and sodium effects on the pressor response to infused norepinephrine

We studied the blood pressure responses to infused norepinephrine in 34 normotensive and 21 unmedicated subjects with essential hypertension. The two groups were similar in age, relative body weight, and urinary electrolyte excretion. Patients were studied on two extremes of dietary salt (200 mEq Na and 10 mEq Na per day). The dose-response curves were highly linear (p less than 0.00001) for both systolic and diastolic blood pressures. There was no evidence for an increased sensitivity to infused norepinephrine among the hypertensive subjects. On the other hand, older subjects had steeper slopes (p less than 0.005). Subjects on a high salt diet had steeper slopes than those on low salt diets (p less than 0.0025); this trend was especially apparent among blacks (p less than 0.005). Black and white hypertensive subjects responded to the high salt diet in opposite fashion: The blacks showed an increased pressor sensitivity (p less than 0.05), whereas the whites demonstrated a nonsignificant decreased pressor sensitivity. These results indicate that age, race, and salt effects must be meticulously controlled in studies of sympathetic nervous system physiology.

Potassium and norepinephrine- or angiotensin-mediated pressor control in pre-hypertension

Blood pressure (BP), plasma electrolytes, renin, aldosterone, angiotensin II (AII) or catecholamines, the chronotropic effects of intravenous isoproterenol, norepinephrine (NE) or AII, the pressor responses to NE or AII, and the relationship between plasma AII and aldosterone concentrations were studied before and after 10 days of dietary supplementation with potassium 100 mmol/day, in normotensive members of normotensive (N = 12) or hypertensive (N = 12) families, and 11 patients with borderline essential hypertension. Under control conditions, the pressor responsiveness to NE was significantly enhanced in normotensive with positive family history for hypertension and hypertensive subjects; the other variables were comparable in the groups. After potassium supplementation, plasma potassium, renin, aldosterone or AII, and the relationship between AII and aldosterone levels increased significantly, while body weight, plasma catecholamines, the chronotropic effects of isoproterenol, AII or NE, the pressor effects of AII and plasma clearance of AII or NE were unchanged in all groups. In normotensive members of hypertensive families and patients with hypertension, BP was decreased and the exaggerated pressor responsiveness to NE was normalized; these variables were not modified in normotensive members of normotensive families. These observations are consistent with a potassium-remediable disturbance in NE- but not AII-dependent regulation of BP in the pathogenesis of essential hypertension.

Adrenergic activity and aldosterone regulation: no evidence for an alpha-1 adrenoceptor-mediated influence in normal subjects

In normal man the sympathetic nervous system could exert an inhibitory influence on aldosterone responsiveness to angiotensin II. The possible role of alpha-1 adrenoceptors in the modulation of aldosterone response was assessed by studying the changes of plasma aldosterone during infusion of angiotensin II at the doses of 1, 2, 5 and 10 ng/kg.min or after corticotrophin injection, 0.25 mg, in 9 normal subjects before and after treatment with the selective alpha-1 adrenoceptor antagonist, prazosin. Prazosin, given during 3 weeks, did not modify supine arterial pressure, heart rate and the plasma levels of angiotensin II, renin, aldosterone or adrenaline but caused a significant (P less than 0.05) increase of plasma noradrenaline. The correlation relating plasma aldosterone to plasma angiotensin II levels before and during angiotensin II infusion and the response of plasma aldosterone to corticotrophin was not modified by prazosin. These findings suggest that in normal man there is no inhibitory influence of the noradrenergic system on aldosterone responsiveness to angiotensin II mediated by an alpha-1 dependent mechanism.