Effects of doxazosin and atenolol on the fibrinolytic system in patients with hypertension and elevated serum cholesterol

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Pharmacological modulation of fibrinolytic response - In vivo and in vitro studies

Fibrinolysis is an action of converting plasminogen by its activators, like tissue- or urokinase-type plasminogen activators (t-PA, u-PA), to plasmin, which in turn cleaves fibrin, thereby causing clot dissolution and restoration of blood flow. Endothelial cells release t-PA, prostacyclin (PGI2) and nitric oxide (NO), the potent factors playing a crucial role in regulation of the fibrinolytic system. Since blood platelets can release not only prothrombotic, but also antifibrinolytic factors, like plasminogen activator inhibitor type-1 (PAI-1), they are involved in fibrynolysis regulation. Therefore agents enhancing fibrinolysis can be preferred pharmacologicals in many cardiovascular diseases. This review describes mechanisms by which major cardiovascular drugs (renin-angiotensin-aldosterone system inhibitors, statins, adrenergic receptors and calcium channel blockers, aspirin and 1-methylnicotinamide) influence fibrinolysis. The presented data indicate, that the influence of these drugs on endothelium-blood platelets interactions via NO/PGI2 pathway is fundamental for its antithrombotic and profibrinolytic action. We also described new approaches for intravital confocal real-time imaging as a tool useful to investigate mechanisms of thrombus formation and the effects of drugs affecting haemostasis and mechanisms of their action in the circulation.

Effects of atenolol or losartan on fibrinolysis and von Willebrand factor in hypertensive patients with left ventricular hypertrophy

OBJECTIVES

To compare the effects of the beta-blocker atenolol with the angiotensin receptor blocker (ARB) losartan on plasma tissue-type plasminogen activator (tPA) activity and mass concentration, plasminogen activator inhibitor-1 (PAI-1) activity, tPA/PAI-1 complex, and von Willebrand factor (VWF).

DESIGN

A prespecified, explorative substudy in 22 patients with hypertension and left ventricular hypertrophy (LVH) performed within randomized multicenter, double-blind prospective study.

RESULTS

After a median of 36 weeks of treatment, there were significant differences between the treatment groups, atenolol versus losartan, in plasma median levels of tPA mass (11.9 vs 7.3 ng/mL, P = .019), PAI-1 activity (20.7 vs 4.8 IU/mL, P = .030), and tPA/PAI-1 complex (7.1 vs 2.5 ng/mL, P = .015). In patients treated with atenolol, median levels of tPA mass (8.9-11.9 ng/mL, P = .021) and VWF (113.5%-134.3%, P = .021) increased significantly, indicating a change toward a more prothrombotic state. No significant changes occurred in the losartan group.

CONCLUSION

Losartan treatment was associated with preserved fibrinolytic balance compared to a more prothrombotic fibrinolytic and hemostatic state in the atenolol group. These findings suggest different fibrinolytic and hemostatic responses to treatment in hypertensive patients with LVH.

The effects of nebivolol on fibrinolytic parameters in mild and moderate hypertensive patients

BACKGROUND

The aim of the present study was to investigate the effects of nebivolol (5 mg daily) on plasma levels of hemostatic and fibrinolytic endothelial function markers in mild or moderate hypertensive patients.

METHODS AND RESULTS

Thirty-five (22 female, 13 male; mean +/- SD 54.7 +/- 11.3 years of age) mild and moderate hypertensive patients were included the study. The mean systolic blood pressure [BP] was 160 mmHg (range 150 mmHg to 165 mmHg) and the mean diastolic BP was 100 mmHg (range 90 mmHg to 100 mmHg). Plasma tissue plasminogen activator antigen (tPA-Ag), plasminogen activator inhibitor type 1 antigen (PAI-1-Ag), PAI-1 activity, tPA-Ag/PAI-1-Ag index, fibrinogen and euglobulin lysis time were determined before and after two months of therapy. tPA-Ag and PAI-Ag levels were measured by ELISA. After this period, treatment with nebivolol (5 mg/day) in all patients was associated with a significant decrease in systolic BP and diastolic BP (P<0.001 for each), heart rate (P<0.01), fibrinogen (P<0.005) and euglobulin lysis time (P<0.01). The tPA-Ag and tPA-Ag/PAI-1-Ag index levels were increased significantly (P<0.001 for each) in all patients, but the PAI-1-Ag (P>0.05) and PAI-1 activity (P>0.05) did not show significant change. In the present study, there was no correlation between decreases in arterial BP and decreases in fibrinolytic parameters (P>0.05), but there was a positive, statistically significant correlation between fibrinogen and body mass index (P<0.001).

CONCLUSIONS

The results indicated that, compared with no treatment, a two-month treatment trial with nebivolol was associated with a more favourable modification of hemostatic and fibrinolytic status in addition to antihypertensive effects.

The role of the alpha-1 adrenoceptor in modulating human mesangial cell matrix production

BACKGROUND

The sympathetic nervous system is frequently activated in hypertension and may modify various aspects of renal function. Whether modulation of the sympathetic nervous system directly influences the development of renal fibrosis is yet to be established. The current study investigates the role of the alpha-1 adrenoceptor on human mesangial cell scarring.

METHODS

Human mesangial cells were injured with macrophage-conditioned medium (MPCM) and treated with doxazosin for 1 or 3 days.

RESULTS

alpha-1 Adrenoceptor antagonist doxazosin of 2 micromol/l reduced fibronectin protein in MPCM-injured female mesangial cells by 31 +/- 1.03% (P < 0.001) and by 9.5 +/- 0.3% (P = 0.01) in male mesangial cells. The differential response between sexes was significant (P = 0.004). alpha-1B Adrenoceptors were detected in human mesangial cells by reverse transcription-polymerase chain reaction with expression in female cells being 87% higher than in males (P = 0.04). Injury with MPCM reduced alpha-1B adrenoceptor mRNA expression in both cell types. Doxazosin had no effect on the protein levels of transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta), however, a small reduction in tumour necrosis factor-alpha (TNF-alpha) levels was observed. Doxazosin had no effect on the modulators of matrix turnover matrix metalloproteinases MMP3, MMP9 and tissue inhibitor of matrix metalloproteinases (TIMP-1), although a significant reduction in tissue plasminogen activator (tPA); (36.5 +/- 2.6%, P < 0.001) was observed. Doxazosin caused an up-regulation of kallikrein expression, both at mRNA and protein levels. Co-treatment with the bradykinin B2 receptor antagonist HOE140 was able to attenuate the effects of doxazosin treatment on fibronectin levels.

CONCLUSION

These data suggest that inhibition of alpha-1B adrenoceptors in mesangial cells exerts an anti-fibrotic effect in a sex-specific manner via modulation of the kallikrein-kinin/plasminogen activator system.

Effect of Doxazosin Gastrointestinal Therapeutic System on Patients with Uncontrolled Hypertension: The ASOCIA Study

OBJECTIVE

To evaluate extended-release doxazosin gastrointestinal therapeutic system (GITS) as add-on therapy in patients with treated, but uncontrolled hypertension.

METHODS

A 16-week, open, noncomparative, multicenter, prospective study of patients with hypertension (> or = 140/> or = 90 mm Hg). Doxazosin GITS 4 mg/d was added to entry medication and increased to 8 mg/d at Week 4 in cases of inadequate blood pressure (BP) control.

RESULTS

A total of 3631 patients (40% women) with mean age of 62.4 +/- 0.2 years were included. Proportion of patients reaching goal (< 140/< 90 mm Hg) after 4 weeks of add-on therapy with doxazosin GITS was 39% and increased to 61% at Week 16. Systolic and diastolic BP (mean +/- SEM) decreased, respectively, from 161.6 +/- 0.2 and 95.1 +/- 0.1 mm Hg at baseline to 142.2 +/- 0.2 and 84.1 +/- 0.1 mm Hg at Week 4 (P < 0.0001) and 136.8 +/- 0.2 and 80.6 +/- 0.2 mm Hg at Week 16 (P < 0.0001). Adverse events occurred in 108 patients (3.0%), with 57 (1.6%) related to the study treatment. In 17 patients (0.5%), serious adverse events were described, but only one was related to the study drug.

CONCLUSIONS

Doxazosin GITS as add-on therapy achieved target blood pressure and was well tolerated in patients with hypertension uncontrolled by previous regimens. Doxazosin GITS efficacy and tolerability was achieved in combination with all classes of antihypertensives tested.

Hemodynamic Effects of α1-Adrenoceptor Antagonist, Doxazosin, in Patients With Chronic Congestive Heart Failure

PURPOSE

Non-selective alpha-adrenoceptor antagonists have not demonstrated significant beneficial effects in chronic heart failure. Previous studies with the selective alpha1-adrenoceptor antagonist, doxazosin, led to conflicting results. We assessed the hypothesis that treatment with doxazosin adjuvant to standard oral therapy results in significant increase in cardiac index in patients with chronic heart failure.

METHODS

A double-blind, randomized study was conducted on 30 patients with chronic congestive heart failure (NYHA III-IV), with cardiac index<2.5 l/minxm, and/or with pulmonary capillary wedge pressure>16 mm Hg. Of the 30 patients, 15 were treated with doxazosin and 15 with placebo, both adjuvant to stable oral therapy, which included a minimum of an ACE inhibitor and a diuretic. Hemodynamic measurements were performed on days 1 and 2, and after 12 weeks on study medication. On day 1, patients were treated with 4 mg doxazosin or placebo. On day 2 and throughout the following 12 weeks, the patients were treated with 4 mg or 8 mg doxazosin/d (the latter, if 4 mg/d did not induce an increase >0.75 l/minxm in cardiac index), or with placebo.

RESULTS

Six patients were treated with 4 mg doxazosin/d (group A), 9 patients with 8 mg doxazosin/d (group B), and 15 with placebo. Baseline values for the cardiac index on day 1, day 2, and after 12 weeks failed to disclose significant differences between patient groups and between the days of study. On day 1, the increase in cardiac index compared with baseline was significantly higher in group A than in the placebo group (P=0.004) and group B (P=0.001). On day 2, the increase in cardiac index compared with baseline on day 1 was significantly higher in group A than in group B (P=0.003) (with reference to alpha/3=0.0167 according to Bonferroni). This was no longer observed after 12 weeks. In the placebo group, following significant changes occurred in baseline values, heart rate was lower (P=0.023) and stroke volume index was higher after 12 weeks in comparison to day 1 (P=0.032).

CONCLUSIONS

In conclusion, oral application of doxazosin supplementary to standard oral medication did not induce sustained hemodynamic benefit. Significant acute increase in cardiac index was observed in a minority (40%) of patients, whereas favorable changes in baseline hemodynamic parameters after 12 weeks occurred in the placebo group.

Is the effect of antihypertensive drugs on platelet aggregability and fibrinolysis clinically relevant?

Hypertension is associated with decreased fibrinolytic potential, mainly expressed as elevated plasma plasminogen activator inhibitor type 1 (PAI-1) levels, and increased platelet aggregability, which may account in part for the increased risk of atherosclerosis and its clinical complications in hypertensive patients. The effects of antihypertensive drugs on this prothrombotic state have been investigated and controversial findings have been reported, possibly because of differences in study designs, patients selected, and methodology used. Scarce and conflicting data exist about the effects of diuretics and beta-adrenoceptor antagonists on the fibrinolytic system, whereas ACE inhibitors have generally been reported to improve the fibrinolytic balance by decreasing plasma PAI-1 levels, calcium channel antagonists have been shown to increase tissue plasminogen activator (tPA) activity, and angiotensin II type 1 (AT(1)) receptor antagonists seem to exert neutral effects. beta-Adrenoceptor antagonists, calcium channel antagonists, and AT(1)-receptor antagonists have been reported to exert anti-aggregatory effects on platelets, while contrasting data exist about the influence of ACE inhibitors. Clinical implications of the changes induced by antihypertensive drugs on the fibrinolytic balance and platelet function are still debated. In particular, the question of whether these changes may translate into different degrees of cardiovascular protection in hypertensive patients remains unanswered. While awaiting more information from clinical trials, the choice of antihypertensive drugs, particularly in high-risk patients, should take into account effects beyond their BP-lowering efficacy. Selected agents should have a favorable, or at least neutral, impact on fibrinolytic function and platelet activity.

Doxazosin, an alpha-1 antagonist, prevents further progression of the advanced atherosclerotic lesion in hypercholesterolemic hamsters

The aim of this study was to examine the effect of doxazosin (DOX) on the further progression and regression of the advanced atherosclerotic lesion in the hypercholesterolemic hamster. Thirty-six, male F(1)B Golden Syrian hamsters, 10 weeks of age, were divided into 3 groups of 12 and fed a nonpurified hypercholesterolemic diet (HCD) containing 10% coconut oil and 0.1% cholesterol (wt/wt) for 9 months (HCD 9). One group of hamsters was euthanized at 9 months and their aortas were collected, fixed, and stored until analysis. The remaining hamsters were either maintained on the HCD for an additional 6 months (HCD 15) or fed the HCD plus 20 mg/kg/d DOX for the 6 months. At the end of the study (15 months), the DOX-treated hamsters had significantly lower plasma total cholesterol (TC) (-68%), low-density lipoprotein-cholesterol (LDL-C) (-73%), and triglycerides (TG) (-74%) compared with the HCD 15. The lumenal narrowing and intimal thickening atherosclerotic lesions were significantly less in the DOX-treated hamsters compared with the HCD 15 (-66% and -70%, respectively). These data suggest that DOX treatment prevents further progression of the advanced atherosclerotic lesion possibly by lowering plasma TC, LDL-C, and TG in hypercholesterolemic hamsters.

Low-dose doxazosin improved aortic stiffness and endothelial dysfunction as measured by noninvasive evaluation

Evaluation of atherosclerosis is important in the treatment of hypertension. To evaluate the preventive effects of a small amount of alpha-blockade, arterial and endothelial dysfunction were measured by noninvasive tests, i.e., pulse wave velocity, acceleration plethysmography and strain-gauge plethysmography, in patients with essential hypertension. Fifteen patients (65+/-3 years old) with essential hypertension (WHO stage I or II) were analyzed in this study. We performed noninvasive evaluations to measure aortic stiffness and endothelial dysfunction, in addition to measuring blood pressure, cholesterol profile, and levels of cells adhesion molecules and nitric oxide before and 6 and 12 months after the start of doxazosin treatment (1.0 mg/day). Blood pressure and heart rate did not significantly change during treatment. The pulse wave velocity index was significantly reduced both at 6 (7.72+/-0.23 m/s; p<0.05) and 12 (7.34+/-0.26 m/s; p<0.05) months after the start of treatment compared to the pretreatment level that at baseline. There was also a significant improvement in b/a after 12 months (-0.46+/-0.04; p<0.05) and in d/a after 6 months (-0.38+/-0.03; p<0.05) and 12 months (-0.39+/-0.03; p=0.05) compared to the pretreatment values. Moreover, reactive hyperemia evaluated by strain-gauge plethysmography after 6 months (1.34+/-0.11; p<0.05) and 12 months (1.49+/-0.16; p<0.05) was significantly improved compared to that before treatment, and NOx was significantly increased after 12 months (89.7+/-15.7 micromol/l; p<0.005). These data suggest that a low dose of doxazosin may play an important role in improving arterial stiffness and endothelial dysfunction without changing cardiac hemodynamics.

Plasminogen activator inhibitor type-1 in cardiovascular disease. Status report 2001

Plasminogen activator inhibitor type-1 (PAI-1) is known to contribute to thrombus formation and to the development and the clinical course of acute and chronic cardiovascular disease, as well as of other arterial and venous thromboembolic diseases. Recently, an important role of elevated pretreatment levels of PAI-1 for failure of thrombolytic therapy of acute myocardial infarction has been discussed. PAI-1 plasma levels depend on the one hand on gene regulation but are related on the other hand to known risk factors of atherosclerosis like insulin resistance, diabetes or hypertriglyceridemia, respectively. Furthermore, an activated renin-angiotensin-aldosterone system (RAAS) significantly contributes to the upregulation of PAI-1 concentration via a receptor-mediated mechanism. In accordance to the known mechanisms of regulation of PAI-1 plasma levels, the use of specific agents like antidiabetic drugs, fibrates, statins, ACE inhibitors and angiotensin II type-1 receptor-blockers may contribute to the downregulation of circulating PAI-1 and, therefore, increase the fibrinolytic capacity and consecutively counteract the thrombotic tendency. To further improve the efficacy of thrombolytic therapy, a PAI-1 resistant variant of t-PA, TNK-t-PA, has been developed and is now available for acute myocardial infarction.

Plasminogen activator inhibitor type-1 (part one): basic mechanisms, regulation, and role for thromboembolic disease

Plasminogen activator inhibitor type-1 (PAI-1) is a rapid inhibitor of tissue plasminogen activator (tPA) in circulation. Evidence suggests that the PAI-1 concentration is responsible for the regulation of the endogenous fibrinolytic system through its tPA/PAI-1 interactions. Accordingly, increased levels of PAI-1 have emerged as a masker for an increased thrombolic risk. This article represents a status report of mechanism of action, regulation of plasma levels, as well as the role of PAI-1 in arterial and venous thromboembolic disease.

Fibrinolytic/hemostatic variables in arterial hypertension: response to treatment with irbesartan or atenolol

Essential hypertension is often accompanied by abnormalities of the coagulation/fibrinolytic system, predisposing to a procoagulant state. The aim of the present study was to compare the effects of atenolol (beta1-blocker agent) and irbesartan (angiotensin II type 1 receptor antagonist) on plasma levels of hemostatic/fibrinolytic and endothelial function markers in a cohort of previously untreated hypertensives. Fifty-four patients were randomly assigned to atenolol 25 to 150 mg (26 patients) or irbesartan 75 to 300 mg (28 patients). The plasma levels of plasminogen activator inhibitor-1 antigen, thrombomodulin, tissue factor pathway inhibitor antigen, fibrinogen, and factor XII were determined before and after 6 months of therapy. Age, gender distribution, body mass index, lipid profile, and baseline values of the measured markers were similar in both groups. Baseline values for systolic and diastolic blood pressure, as well as the reduction after treatment, were not significantly different between the two groups. Treatment with irbesartan was associated with a significant decrease in the levels of all the parameters. Similar findings were observed in the atenolol group, except for factor XII and tissue factor pathway inhibitor levels, which were not significantly decreased in this group. The reduction, however, of fibrinogen, plasminogen activator inhibitor-1, and thrombomodulin was significantly greater in the irbesartan than in the atenolol group. In conclusion, the results indicated that, despite an equally controlled blood pressure, 6-month therapy with irbesartan was associated with a more favorable modification of hemostatic/fibrinolytic status than atenolol.

Platelet alpha2-adrenoceptor alterations in patients with essential hypertension are normalized after treatment with doxazosin but not propranolol

OBJECTIVE

Marked alterations have been demonstrated to occur in the platelet alpha2-adrenoceptors of patients with essential hypertension. The purpose of this study was to determine whether antihypertensive treatment with alpha-adrenergic blocker doxazosin or beta-adrenergic blocker propranolol can affect the affinity and the density of platelet alpha2-adrenoceptors in such patients.

SUBJECTS AND METHODS

In two groups of 22 previously untreated, essential hypertensive patients, the mean affinity (Kd) and density (B(max)) of platelet alpha2-adrenoceptors were studied by [3H]-UK 14304 binding assays; the first assays were performed before any medication was begun, the second were performed after treatment for up to 13 weeks with doxazosin or propranolol. A third group of 22 healthy normotensive volunteers matched by age, sex and body mass index was used as control.

RESULTS

Blood pressure did not differ significantly in the two hypertensive groups, and treatment with the two drugs resulted in closely similar, normal blood pressure levels. Kd and B(max) values were significantly higher in the two hypertensive groups than in controls. After treatment with propranolol the binding parameters did not change significantly, whereas after treatment with doxazosin Kd and B(max) returned to normotensive values.

CONCLUSIONS

In previously untreated, essential hypertensive patients platelet alpha2-adrenoceptors have a lower affinity but a higher density than in normotensive subjects. Despite similar effects on blood pressure, the treatment with the alpha-adrenergic blocker doxazosin is followed by restoration of normal findings in the binding assays of platelet alpha2-adrenoceptors whereas the treatment with the beta-adrenergic blocker propranolol does not alter the Kd and B(max) values.

Blood pressure control, microalbuminuria and cardiovascular risk in Type 2 diabetes mellitus

Type 2 (noninsulin-dependent) diabetes mellitus (DM) affects about 3% of the UK population. Diabetes often coexists with a cluster of other potent cardiovascular risk factors, including hypertension, dyslipidaemia and increased tendency for thrombosis, and increases the risk of early death from cardiovascular causes by about threefold. Microalbuminuria or proteinuria also may be present, further increasing the risk of cardiovascular mortality. Cardiovascular risk factors must be treated aggressively in patients with Type 2 diabetes and control of blood pressure at 140/85 mm Hg or lower is a priority. The management of hypertension in patients from some ethnic groups demands special consideration because they have a high incidence of diabetes and hypertensive complications. Patients must be urged to adopt appropriate lifestyle changes in the first instance but additional drug treatment for hypertension is usually required. All the major classes of antihypertensive agents lower blood pressure in Type 2 diabetic patients but have different effects on metabolic risk factors in different ways. Low-dose thiazide diuretics, beta-blockers, calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors have been shown to reduce cardiovascular risk. Individually, the effects of low-dose thiazide diuretics and beta-blockers on glucose and lipid metabolism is clinically insignificant, though in combination much larger metabolic effects are seen. ACE inhibitors and calcium channel blockers have no, or small, beneficial effects on glucose and lipid metabolism, while the greater beneficial effects of alpha1-blockers on lipid profiles may render them especially useful in the Type 2 diabetic patient. Long-acting calcium-channel blockers and ACE inhibitors protect renal function and are suitable as first line therapy in patients with microalbuminuria or proteinuria. Until results from the current batch of randomized, placebo-controlled trials comparing different classes of antihypertensive agents are available, the choice of antihypertensive agent is difficult. Addressing overall cardiovascular risk factors, rather than hypertension alone, is essential in the management of the hypertensive Type 2 diabetic patient.

Effects of doxazosin and atenolol on atherothrombogenic risk profile in hypertensive middle-aged men

The alpha-blockers prazosin and doxazosin reduce hypertriglyceridemia (HTG) and increase serum levels of high-density lipoprotein (HDL)-cholesterol, whereas beta-blockers such as atenolol have the opposite effect. As HTG is associated with reduced fibrinolysis and hypercoagulability, we investigated the effects of doxazosin and atenolol on serum lipids and hemostatic factors in hypertensive men with an atherothrombogenic risk profile. The study was randomized and open, but blinded to investigator of biochemical results. Forty-five men (mean age, 44.5 years) with central obesity [median body-mass index (BMI), 28 kg/m2] and moderate hypertension [median diastolic blood pressure (DBP), 104.5 mm Hg] were treated with atenolol (n = 22) or doxazosin (n = 23) for 22 weeks, after which changes in between-group differences from baseline were estimated. After intervention, significant between-group differences in favor of doxazosin were found: lower triglycerides (p = 0.008) and higher HDL cholesterol (p = 0.036); furthermore, improvement of fibrinolysis: lower plasminogen activator inhibitor-1 (PAI-1) activity (p = 0.012), higher tissue plasminogen activator (tPA) activity after venous occlusion (VO); and higher levels of serum D-dimer, both unstimulated (p = 0.0016) and after VO (p = 0.0032). In addition, lower levels of serum testosterone were found in the atenolol group (p = 0.0016). A profile with reduced HTG, increased HDL cholesterol, and improved fibrinolysis was obtained with doxazosin when compared with atenolol. Furthermore, the observed decrease in serum testosterone on atenolol treatment would rather favor long-term treatment with doxazosin in this study population.

Increased levels of tissue plasminogen activator antigen in essential hypertension. A population-based study in Sweden

OBJECTIVE

To investigate components of the haemostatic and fibrinolytic system in borderline hypertensives and hypertensives, drug-treated or not, from a defined population.

DESIGN AND METHODS

A randomly selected sample of the population of northern Sweden, 1558 subjects aged 25-64 years, was studied. Eight per cent of them were being treated with antihypertensive drugs (trHT). Remaining subjects were classified according to their mean diastolic blood pressure (DBP). Normotension, DBP < 85 mmHg, was found in 63%, borderline hypertension (bHT), DBP 85-94 mmHg, in 21% and untreated hypertension (uHT), DBP > or = 95 mmHg, in 8% of the subjects.

RESULTS

Mean age increased from the normotensive group through the bHT and uHT groups to the trHT group, members of which were the oldest. Age-adjusted values for the body mass index, waist: hip ratio, serum triglyceride and Phadeseph plasma insulin levels increased with each level of hypertension. Plasma fibrinogen levels and plasminogen activator inhibitor type 1 activity (in men) increased stepwise from normotensives through bHT and uHT to the highest values found in the trHT group. The tissue plasminogen activator (tPA) activity in men declined strongly across the groups, trHT having the lowest fibrinolytic activity (P < 0.001). tPA antigen levels increased strongly from normotensives through bHT to uHT, but then were lower in the trHT group. Even after adjustment for possible confounders, men in the uHT group had 21% higher (P = 0.027) tPA antigen levels than did the normotensives. In bHT men, the tPA antigen and plasminogen activator inhibitor type 1 activities were 14 and 24% respectively, higher (P < 0.01) than those in the normotensives.

CONCLUSION

Hypertension is associated with multiple metabolic and fibrinolytic disturbances that are accentuated in drug-treated hypertensives and already discernible in subjects with borderline hypertension. Decreased fibrinolysis is associated with, and possibly secondary to, metabolic disturbances linked to the insulin-resistance syndrome. The independent increase in tPA antigen in hypertensive men might indicate an endothelial dysfunction.

Effect of doxazosin on fibrinolysis in hypertensive patients with and without insulin resistance

The fibrinolytic and metabolic changes associated with doxazosin treatment were evaluated in 20 patients with mild to moderate hypertension. Steady-state plasma glucose (SSPG) concentration was used to subdivide hypertensive patients into two groups of 10 each: Insulin-resistant (SSPG > 190 mg/dl) and nonresistant (SSPG < 190 mg/dl). The blood pressure was normalized after 4 to 6 months of doxazosin treatment in both groups, but it was associated with significantly lower fasting plasma triglyceride level, lower integrated insulin response to a 75 gm oral glucose load, lower SSPG concentration, significant decreases in plasma plasminogen activator inhibitor type one antigen and activity and tissue plasminogen activator antigen, and a significant increase in tissue plasminogen activator activity only in the insulin-resistant group but not in the nonresistant group. It was also noted that the improvement of the fibrinolytic and metabolic abnormalities in the insulin-resistant group tended to return to the less abnormal levels seen in the non-resistant group. The data suggested that doxazosin treatment of hypertension attenuated much of the abnormalities of insulin resistance but had little effect on insulin-sensitive patients. It may support a link between impaired fibrinolysis and insulin resistance in patients with hypertension.

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.

Effects of antihypertensive drugs on coronary artery disease risk: a meta-analysis

1. The effects of antihypertensive drugs on lipids may also influence their effect on coronary artery disease (CAD). However, the clinical significance of these effects and the extent to which they persist during long-term therapy is uncertain. 2. We performed a meta-analysis on 23 randomized trials published between 1988 and 1994 that compared the effects of atenolol, celiprolol (a beta-blocker with beta 2-adrenoceptor intrinsic sympathomimetic activity), enalapril, nifedipine and doxazosin on plasma cholesterol, low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), triglycerides and blood pressure (BP). 3. Predicted changes in CAD risk were calculated by incorporating the results for these parameters into the Framingham equations. 4. While there were no differences in antihypertensive efficacy between the drugs, atenolol significantly (P < 0.05) reduced HDL-C and increased total cholesterol, LDL-C and triglycerides compared with celiprolol, enalapril, doxazosin and nifedipine. 5. The magnitude of the effects on lipids was not significantly influenced by the duration of therapy (up to 3 years for atenolol and doxazosin and up to 2 years for celiprolol). 6. The improvement in Framingham equation point scores (systolic BP formula) was significantly (P < 0.05) less for atenolol (-0.54; confidence intervals (CI) -0.29-(-0.78)) than for celiprolol (-1.69; CI -0.68-2.70), doxazosin (-1.67; CI -1.11-(-2.23)), enalapril (-1.43; CI 0.23-(-3.07)) and nifedipine (-1.91; CI -1.22-(-2.59)). Similar results were obtained for the Framingham diastolic BP formula. 7. These results suggest that the adverse effects of atenolol ]on plasma lipids do not improve with prolonged therapy and are theoretically great enough to reduce its efficacy in reducing CAD by approximately two thirds compared with antihypertensive drugs that do not adversely affect plasma lipids. However it must be emphasized that these are theoretical effects. In order to determine the actual differences between these drugs on CAD end points, studies using these end points are required.

Doxazosin. An update of its clinical pharmacology and therapeutic applications in hypertension and benign prostatic hyperplasia

Doxazosin is a long-acting alpha 1-adrenoceptor antagonist structurally related to prazosin and terazosin. Its antihypertensive effect is produced by a reduction in the smooth muscle tone of peripheral vascular beds resulting in a decrease in total peripheral resistance without significant effect on cardiac output or heart rate. In benign prostatic hyperplasia, doxazosin's effect of relieving bladder outflow obstruction is produced through a reduction in prostatic tone mediated via alpha 1-adrenoceptor blockade. In most comparative trials doxazosin has proven to be equally effective as the comparator drug in the treatment of mild to moderate hypertension. It has been used in a variety of patient populations including the elderly, Blacks, smokers, and patients with concomitant disease states such as renal dysfunction, hypercholesterolaemia, non-insulin dependent diabetes mellitus (NIDDM) and respiratory disease. Doxazosin has also been used successfully in combination with beta-adrenoceptor antagonists, diuretics, calcium channel antagonists, and angiotensin-converting enzyme inhibitors in patients with hypertension that is uncontrolled with monotherapy. Doxazosin has a beneficial effect on some of the risk factors associated with coronary heart disease including elevated serum lipid levels, impaired glucose metabolism, insulin resistance and left ventricular hypertrophy. Modest decreases in total cholesterol, low density lipoprotein cholesterol and triglycerides are seen with doxazosin therapy while small increases in high density lipoprotein cholesterol and the high density lipoprotein cholesterol/total cholesterol ratio are consistently reported. Some studies have reported an improvement in glucose tolerance although this effect has been more consistently seen in nondiabetic patients than in patients with NIDDM. Additionally, doxazosin produces a similar reduction in left ventricular hypertrophy to other antihypertensive agents. Modelling-based calculations suggest that doxazosin significantly reduces the risk of developing coronary heart disease in patients with mild to moderate hypertension, although this remains to be confirmed in long term prospective studies. Doxazosin appears to be a promising agent in the treatment of urinary symptoms associated with benign prostatic hyperplasia. Similar to other alpha 1-adrenoceptor antagonists, doxazosin treatment produces increases in peak and mean urinary flow rates and improves other objective and symptomatic measures.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of doxazosin on platelet aggregation, platelet adhesion and blood coagulation in cynomolgus monkeys

The effect of doxazosin, a selective alpha-1 adrenergic inhibitor, on hemostasis was investigated in 9 cynomolgus monkeys. During 12 weeks of doxazosin treatment (1 mg/kg per day), serum lipids, lipoprotein cholesterols, blood coagulation, platelet aggregation and template bleeding times were measured and compared with predrug values. In addition, platelet adhesion to cultured human umbilical vein endothelial cells (HUVEC) in the presence or absence of doxazosin was evaluated. Platelet aggregation was also determined in monkeys following chronic oral exposure to aspirin (162 mg/day). Doxazosin administration was associated with significant reductions in serum total cholesterol (TC) (-16%) and low density lipoprotein cholesterol (LDL-C) (-23%), while high density lipoprotein cholesterol (HDL-C) levels increased 66%. Doxazosin did not alter any parameters of blood coagulation measured; however, bleeding times were increased significantly (33%) in doxazosin-treated animals. Although collagen-stimulated platelet aggregation was not influenced by either chronic doxazosin or aspirin treatment, the maximal extent of ADP-stimulated platelet aggregation was significantly reduced (-26% and -18%, respectively) compared with the control monkeys. Platelets from untreated control animals displayed reductions in the extent of ADP-stimulated aggregation of 13% and 23%, respectively, when incubated in vitro with 200 and 300 micrograms/ml of doxazosin. Additionally, the decrease in aggregation response of platelets obtained from doxazosin-treated monkeys was accompanied by a rapid reversal of platelet aggregation. Adhesion to HUVEC by platelets isolated from doxazosin-treated animals was significantly decreased; however, adhesion was not altered when platelets from untreated control animals were incubated with HUVEC in the presence of doxazosin. Thus, the ex vivo and in vitro studies reported in this communication suggest that doxazosin administration to nonhuman primates is associated with beneficial alterations in plasma lipids, platelet aggregation, bleeding times and platelet adhesion to endothelial cells, parameters which are thought to influence risk of cardiovascular disease in both animals and humans.