Comparison of the effects of doxazosin and atenolol on blood pressure and blood lipids: a one-year, double-blind study in 228 hypertensive patients

Effect of alpha1-adrenergic receptors in cardiac pathophysiology

Compelling evidence now exists that proves adrenergic blockade is at the center of neurohormonal antagonism in heart failure (HF). Catecholamines are well known to act through both beta- and alpha-adrenergic receptors (ARs), which mediate their effects through distinct receptor pathways. Beta-AR blockers are commonly used in the treatment of HF and have distinct receptor affinity profiles. The recent COMET trial comparing 2 important beta-blocking drugs showed a distinct advantage for carvedilol in decreasing the risk of mortality from HF. The mechanism of action for carvedilol differs from metoprolol tartrate in its ability to block both alpha- and beta-ARs, leading to renewed interest in the potential role of alpha-ARs in the progression of HF. In contrast, however, the ALLHAT study discontinued use of doxazosin, an alpha1-receptor blocker because of an increase in cardiovascular events among patients using this drug. The results of these studies appear to be in contrast with respect to the role of alpha-ARs in regards to cardiovascular pathophysiology. Further study of the alpha-receptor and understanding the role of alpha-ARs in HF is necessary to understand the therapeutic effect of alpha-blockade. This article reviews our understanding of the alpha-AR in HF.

Treatment of hypertensive and hypercholesterolaemic patients in general practice. The effect of captopril, atenolol and pravastatin combined with life style intervention

OBJECTIVE

To elucidate the effect on blood pressure and blood lipids of an angiotensin converting enzyme inhibitor (captopril), and a beta-receptor blocking agent (atenolol), given alone or in combination with a cholesterol reducing drug, the beta-hydroxy-methylglutaryl-coenzyme A reductase inhibitor pravastatin, in patients who were also encouraged to improve their lifestyle.

DESIGN

A longitudinal study consisting of three phases. I: Lifestyle intervention alone. II: Continued lifestyle intervention combined with captopril or atenolol. III: Continued lifestyle intervention combined with the same drugs as in phase II and in addition pravastatin or placebo.

SETTING

Fifty-four general practice surgeries in Norway.

PARTICIPANTS

Hypertensive patients, 210 females and 160 males, treated or untreated with antihypertensive drugs with a sitting diastolic blood pressure between 95 and 115 mmHg and a serum total cholesterol between 6.5 mmol/l (7.0 for those age 60-67 years) and 9.0 mmol/l.

RESULTS

The antihypertensive effect of captopril and atenolol was not influenced by concurrent administration of pravastatin. The effect of pravastatin was not limited by concurrent medication with captopril or atenolol. Improvement in lifestyle seemed to reduce the need for supplementary treatment with diuretics.

CONCLUSION

Pravastatin can be used in combination with captopril or atenolol in the treatment of hypertensive and hypercholesterolaemic patients.

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.

A 5-year comparison of doxazosin and atenolol in patients with mild-to-moderate hypertension: effects on blood pressure, serum lipids, and coronary heart disease risk

The long-term efficacy and safety of once-daily treatment with doxazosin or atenolol were compared in a 5-year study in patients with mild-to-moderate hypertension. The study consisted of a 1-year, multicenter, double-blind, parallel-group phase, followed by a 4-year, open-label extension phase. Of the 228 patients enrolled, 100 patients (54/111 doxazosin and 46/117 atenolol) completed the 5-year study. Both treatments were similarly efficacious in controlling blood pressure. As assessed by the Framingham risk equation, which incorporates lipid parameter values, patients receiving doxazosin had significantly less chance of developing coronary heart disease (CHD) within 10 years compared with those patients receiving atenolol (p < 0.05). Doxazosin significantly (p=0.0005) reduced the mean CHD risk from baseline to final visit by 12.3%; whereas, atenolol produced essentially no change in mean risk (0.2% increase). In patients receiving doxazosin, statistically significant (p < 0.05) increases from baseline were observed in serum concentrations of high-density lipoprotein (HDL) cholesterol and the HDL/total cholesterol ratio during the first 2 and 3 years of treatment, respectively. In contrast, significant (p < 0.05) percent reductions from baseline in both these lipid parameters were seen in atenolol-treated patients during most of the 5-year trial. Between-group differences were statistically significant (p < 0.01) at all time points. Decreases in total cholesterol were similar between the two treatment groups. Triglycerides, however, significantly increased with atenolol treatment (p < 0.0001 vs baseline) while remaining essentially unchanged with doxazosin treatment. The safety profiles of doxazosin and atenolol were comparable. Thus, while demonstrating similar antihypertensive efficacy and safety during this 5-year study, once-daily treatment with doxazosin produced a significantly greater beneficial effect on both 10-year CHD risk and serum lipid parameters compared with atenolol.

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)

Lipids and lipoproteins during antihypertensive drug therapy. Comparison of doxazosin and atenolol in a randomized, double-blind trial: the Alpha Beta Canada Study

A randomized double-blind trial comparing the alpha-adrenergic blocker doxazosin and the beta-adrenergic blocker atenolol was completed by 131 patients with mild to moderate hypertension. Blood pressure and fasting blood lipids were determined at baseline and 4, 12, and 24 weeks of treatment. At entry, plasma lipids and lipoproteins were similar in those patients randomized to doxazosin or atenolol. After 24 weeks of treatment with atenolol, there were significant (P < .05) decreases in high-density lipoprotein cholesterol (HDL-C) and increases in triglycerides and very-low-density triglycerides (VLDL-T). In contrast, doxazosin was associated with significant (P < .05) increases in HDL-C and decreases in triglycerides and VLDL-T. There were no significant differences in HDL apolipoprotein (apo) A-I or low-density lipoprotein apoB between the drugs, but atenolol decreased the ratio of HDL-C to apoA-I, and doxazosin increased this ratio, differences that were statistically significant (P < .002). Neither apoA-I nor apoB concentration at baseline nor apoE phenotype was predictive of the lipid responses during antihypertensive treatment with either drug. Thus, there are significant favorable changes in HDL-C, total triglycerides, and VLDL-T between patients with mild to moderate hypertension and normal plasma lipids when treated with the alpha-blocker doxazosin compared with the beta-blocker atenolol. Plasma lipid or apo concentrations were not predictive of their lipid response during antihypertensive therapy with either of these agents.

A double-blind comparison of the effects of carvedilol and captopril on serum lipid concentrations in patients with mild to moderate essential hypertension and dyslipidaemia

We have studied 250 patients with mild to moderate essential hypertension (diastolic blood pressure 95-114 mmHg) and dyslipidaemia (high-density lipoprotein cholesterol (HDL-C) below 1.03 mmol.l-1, total cholesterol 5.17-9.05 mmol.l-1, and triglycerides 2.26-5.64 mmol.l-1) in a controlled double-blind, multicentre, parallel group trial. The patients took a fat-modified diet. After a 4-week placebo period, patients who continued to fulfil the selection criteria were randomly allocated to treatment with either carvedilol (a vasodilating beta-blocker) 25-50 mg o.d. (n = 116) or captopril (an ACE inhibitor) 25-50 mg o.d. (n = 117) for 6 months. In both groups there were favourable effects on the serum lipids. The relative changes (medians) in the carvedilol and captopril group were respectively: increase in HDL-C by 11% and 8%, decrease in total cholesterol by 11% and 10%, in low-density lipoprotein cholesterol by 16% and 12%, and in triglycerides by 13% and 14%. Equivalence of the two treatments was confirmed for the target variable change in HDL-C at a significance level of 5%. Reductions in supine systolic/diastolic blood pressures were comparable in the two groups (carvedilol: 23/19 mmHg, captopril: 20/18 mmHg). The improvement in lipid metabolism in patients treated with carvedilol is probably due to its alpha 1-blocking properties.

Relationships between blood pressure and lipids in childhood

This review has discussed the potential interrelationships of elevated blood pressure and lipid abnormalities. Most of the data for this review have been collected in adults, but physiologic and genetic effects may have expression in childhood. Clustering of cardiac risk factors may be mediated by increased levels of insulin. These increased levels of insulin may be genetically determined or may be related to obesity. Recognition of the multiple risk factor phenotype is important, because individuals with multiple risk may have a much higher risk of future coronary events than do individuals with single risk factors. Medical therapy of individuals with multiple risk should be more aggressive than for individuals with single risk factors. Physicians should be cautious about therapy in the pediatric setting because of possible interaction between therapeutic agents and risk factors, however.

Antihypertensive therapy in the geriatric patient: II. A review of the alpha1-adrenergic blocking agents

The prevalence of hypertension increases with age. Multiple physiologic factors are involved in the development of hypertension in the elderly. Alpha1-adrenergic blocking agents lower blood pressure through a reduction in total peripheral resistance. Prazosin, terazosin, and doxazosin have been shown to be equally effective in reducing blood pressure in older persons. The bioavailability, terminal elimination half-life, and volume of distribution of prazosin is increased in the elderly. Hybrid drugs, such as ketanserin, urapidil, and indoramin are also effective in lowering blood pressure. Ketanserin seems to have a greater effect on blood pressure reduction in persons older than 60 years of age. Alpha1-adrenergic blockers may be used safely in patients with diabetes, asthma, and hyperlipidemia.

Doxazosin and captopril in mildly hypercholesterolemic hypertensive patients. The Doxazosin-Captopril in Hypercholesterolemic Hypertensives Study

The evidence linking hypertension and hypercholesterolemia is strong and has fueled research into possible adverse effects of some antihypertensive agents on serum lipid profile. This multicenter, open, parallel study compares the effects of doxazosin and captopril on blood pressure, serum lipid levels, and quality of life in 224 hypercholesterolemic hypertensive patients. Blood pressure was significantly reduced in both treatment groups (p < 0.001) and was normalized (standing diastolic pressure < or = 90 mm Hg) in 73% of the doxazosin patients and 67% of the captopril group. Serum total cholesterol level was favorably reduced by both doxazosin (from 238 to 223 mg/dl, p < 0.001) and captopril (from 245 to 233 mg/dl, p < 0.001), whereas high density lipoprotein cholesterol concentration increased only in the doxazosin group (from 33 to 36 mg/dl, p < 0.001). The calculated 10-year risk for the development of coronary heart disease was reduced significantly (p < 0.001) by 28% in the doxazosin group and by 19% in the captopril group. The quality of life evaluation showed beneficial changes in both treatment groups. As a result of proven antihypertensive efficacy and a lack of unfavorable effects on lipid parameters and health status measures, these findings support the use of both doxazosin and captopril as agents of first choice in the treatment of hypertensive patients with associated lipid abnormalities.

Clinical implications of pathophysiologic changes in the midlife hypertensive patient

Both aging and hypertension decrease cardiac output through a lower stroke volume and a diminished beta-adrenergic responsiveness. In parallel, the vascular resistance increases because of vascular hypertrophy. In addition, in hypertension the alpha-adrenergic responsiveness is enhanced. Aging and hypertension are also associated with an increase in plasma cholesterol and insulin values. These alterations in cholesterol and insulin levels become particularly pronounced in middle-aged patients with hypertension. alpha-Adrenergic-blocking agents have a positive effect on lipids and insulin resistance. The shift toward enhanced alpha-adrenergic responsiveness, and the fact that vasodilators do not diminish exercise performance favor the use of alpha-blockers as a first drug in middle-aged patients with hypertension. Blood pressure lowering still remains the paramount goal, and these compounds should be used only if proved to be efficacious in a given individual patient.

Selective alpha 1-adrenoreceptor blockers in the treatment of hypertension: should we be using them more?

It has become apparent in recent years that in the treatment of essential hypertension, reduction of blood pressure alone is not sufficient to reduce significantly the morbidity and mortality from ischaemic heart disease. Since the emergence of a multifactorial approach to the prevention of cardiovascular disease, the potential interaction between antihypertensive therapy and metabolic factors, such as control of blood glucose and lipid levels, has become an important consideration. Abnormal function of the sympathetic nervous system may contribute to both the initiation, or maintenance, of hypertension and the associated metabolic disturbances. The new generation of selective alpha 1-adrenoreceptor blockers, besides lowering blood pressure, appear to have favourable effects on lipid and glucose metabolism. The use of these drugs and their place in the treatment of hypertension are discussed.

Antihypertensive agents, serum lipoproteins and glucose metabolism

Effective blood pressure control with traditional high-dose diuretic therapy has led to a distinct decrease in cerebrovascular morbidity and mortality, but failed to achieve a satisfactory reduction of coronary complications and sudden death. The same applies also for beta blockers, although they have been shown to be effective in secondary prevention of myocardial infarction. It is suspected that conventional antihypertensive treatment has an unfavorable effect on coronary risk factors other than hypertension. For instance, thiazide-type diuretics can impair glucose tolerance and increase the potentially atherogenic serum low-density lipoprotein (LDL) cholesterol fraction and triglycerides. Beta blockers without partial intrinsic sympathomimetic activity increase serum triglycerides and tend to lower the potentially antiatherogenic high-density lipoprotein (HDL) cholesterol. Certain beta blockers may also impair glucose tolerance, particularly when they are combined with diuretics. Calcium channel blockers, angiotensin converting-enzyme inhibitors and alpha 1-receptor blockers do not adversely affect lipoprotein or carbohydrate profiles. The latter two drug classes may even increase insulin sensitivity, and alpha 1 blockers may also slightly improve lipid metabolism. The prognostic relevance of drug-induced dyslipidemia and/or glucose intolerance awaits further clarification. In the meantime, it is of clinical interest that several of the generally available antihypertensive drugs seem to be metabolically neutral or sometimes perhaps even potentially beneficial with regard to the lipoprotein and carbohydrate metabolism.

A double-blind comparative study of doxazosin and prazosin when administered with beta-blockers or diuretics

The antihypertensive efficacy and safety of doxazosin (once daily) and prazosin (twice daily) were compared in patients with mild or moderate essential hypertension (diastolic blood pressure [DBP] 95 to 114 mm Hg) not adequately controlled by diuretics and beta-blockers. Doxazosin produced significantly greater mean reductions in standing (p = 0.01) and supine (p = 0.04) DBP than did prazosin; there were no significant between-group differences in either mean systolic blood pressure or heart rate. The overall mean daily doses for efficacy-evaluable patients were 4.7 mg of doxazosin and 6.7 mg of prazosin. Sixteen patients (84.2%) treated with doxazosin and 13 patients (56.5%) treated with prazosin were considered therapeutic successes (decrease in standing DBP greater than or equal to 10 mm Hg or to less than or equal to 90 mm Hg with greater than or equal to 5 mm Hg reduction from baseline). Of the 19 efficacy-evaluable patients treated with doxazosin, 15 (78.9%) showed improvement in the severity category of hypertension; an improvement in severity was reported in 14 patients (60.9%) treated with prazosin. Doxazosin produced a more favorable effect on serum lipid levels than did prazosin, although no statistically significant within- or between-group differences were observed. Most side effects experienced with either doxazosin or prazosin were mild or moderate and were tolerated or disappeared with continued treatment. The overall evaluation of toleration was excellent or good for 18 (90%) doxazosin- and 21 (91%) prazosin-treated patients. Clinical efficacy was rated as excellent or good for 16 patients (80%) treated with doxazosin and 15 patients (68%) treated with prazosin.

Efficacy of doxazosin in specific hypertensive patient groups

In practice, some of the major problems for the physician who treats hypertension are patients who are resistant to treatment or who have other complicating risk syndromes. Therefore the overall efficacy of an antihypertensive agent must include an assessment of effect in patients with serious ancillary problems. In this article, doxazosin is reviewed for its efficacy in the treatment of severe essential hypertension and specific complications or conditions of mild or moderate essential hypertension, namely, left ventricular hypertrophy, hyperlipidemia, noninsulin-dependent diabetes mellitus, renal insufficiency, pheochromocytoma, chronic obstructive pulmonary disease, peripheral vascular disease, and smoking. Doxazosin is particularly efficacious in many specific subgroups of patients with hypertension, and the results of relevant studies are discussed.

The addition of doxazosin to the treatment regimen of patients with hypertension not adequately controlled by beta-blockers

When doxazosin was given to patients with hypertension not adequately controlled by beta-blockade, blood pressure was normalized in 94% of the 34 patients (blood pressure less than or equal to 140/85 mm Hg). This reduction in blood pressure was obtained with doxazosin in combination with metoprolol or oxprenolol at a mean final daily dose of 1.3 mg or pindolol or atenolol at 2.0 mg/day. Exercise-induced increase in systolic and diastolic blood pressure was also lower with combined beta-blocker and doxazosin therapy than with beta-blocker alone. After 12 weeks of treatment, the combination of doxazosin and beta-blocker significantly reduced total serum cholesterol and triglyceride levels. All side effects were mild and only one patient was withdrawn from therapy.

Doxazosin and atenolol as monotherapy in mild and moderate hypertension: a randomized, parallel study with a three-year follow-up

The efficacy and safety of doxazosin (n = 83) and atenolol (n = 81) have been compared during a 3-year period. Doxazosin (mean dose at 3 years, 5.2 mg/day) and atenolol (mean dose, 66.4 mg/day) produced a sustained and overall similar reduction in blood pressure, with no evidence of tolerance. Doxazosin decreased mean blood pressure from 158/104 mm Hg to 146/90 mm Hg; with atenolol the decrease was from 160/103 mm Hg to 144/88 mm Hg. Whereas the reduction in blood pressure with atenolol was paralleled by a significant (p less than 0.05) decrease in heart rate (from a mean of 74 to 60 beats/min), doxazosin produced no clinically meaningful changes in heart rate. In contrast to atenolol, doxazosin reduced triglyceride levels by -5.9% (atenolol +22.5%), increased high-density lipoprotein cholesterol levels by +3.7% (atenolol, -11.2%), and increased the high-density lipoprotein/total cholesterol ratio by +5.9% (atenolol, -10.3%); all of these values were significantly (p less than 0.001) different from those of atenolol-treated patients. Doxazosin also reduced the calculated low-density lipoprotein cholesterol levels by -3.3% (atenolol, unchanged). The adverse effect of atenolol on lipid levels apparently negated any beneficial effect of blood pressure reduction, because the calculated coronary heart disease (CHD) risk actually increased significantly. In contrast, the reduction in calculated CHD risk in the doxazosin group was statistically significant at all points during the study. The safety profile of the drugs was similar. With the added potential of the reduction in the calculated risk of CHD among hypertensive patients,doxazosin represents an appropriate first-line drug for the treatment of essential hypertension.

Preliminary results of the Norwegian doxazosin postmarketing surveillance study: a twelve-week experience

The study was designed to investigate the safety and efficacy of doxazosin in the control of blood pressure in general medical practice; the results presented concern the first 748 patients evaluated over a 12-week period. Blood pressure was significantly reduced after treatment with doxazosin (-13/-9 mm Hg), and heart rate was not significantly altered. In addition, doxazosin significantly reduced total cholesterol levels (-6.7%), reduced triglyceride levels (-19.8%), increased high-density lipoprotein cholesterol levels (+2.5%), and the high-density lipoprotein:total cholesterol ratio (+9.7%). The calculated risk of coronary heart disease was reduced by 20.5% over a 12-week period. Thirty-five percent of patients reported at least one side effect, and the number of patients experiencing severe adverse reactions was small. Twenty patients (2.7%) discontinued treatment because of adverse events, and 2.7% had the dose of doxazosin reduced.

Doxazosin: a study in a cohort of patients with hypertension in general practice--an interim report

The objective of this study was to assess the safety and efficacy of doxazosin in a substantial cohort of hypertensive patients drawn from general practice. A total of 4027 patients entered the study, 1472 of whom (36.6%) were untreated hypertensive patients. Patients were not advised to change diet, smoking habit, or life-style during the study. Twenty-one percent were cigarette smokers, and concurrent diabetes was present in 2.3%. Baseline blood cholesterol exceeded 200 mg/dl (5.2 mmol/L) in 90% and 250 mg/dl (6.5 mmol/L) in 56% of patients. The mean decrease in blood pressure produced by doxazosin was 22/15 mm Hg after 10 weeks of therapy; there was a mean decrease in heart rate of 1 beat/min. The mean maintenance dose for all patients was 3.1 mg/day. Side effects considered related or possibly related to treatment were reported in 705 patients. Treatment was discontinued in 233 patients (5.8%) because of adverse events related or possibly related to treatment with doxazosin. Doxazosin produced a significant (p less than 0.001) decrease in total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels and a significant increase in high-density lipoprotein cholesterol and the ratio of high-density lipoprotein:total cholesterol. The potential reduction in 10-year coronary heart disease risk (according to the Framingham equation) was calculated to be 20.4%.

Efficacy and safety of doxazosin in the treatment of patients with mild or moderate essential hypertension and elevated levels of cholesterol

In hypertensive patients, elevated serum cholesterol is a frequent and sinister additional coronary risk factor. Selective alpha 1-adrenoreceptor inhibitors appear to have the unique ability to control both risk factors. Forty-two patients, ages 42 to 65 years, including 21 men with sustained hypertension and elevated serum cholesterol levels, were included in a trial of monotherapy with doxazosin administered once daily (range, 1 to 16 mg). The influence of the drug on high blood pressure and elevated serum cholesterol was evaluated over a 28-week period, which consisted of a 4-week, single-blind placebo lead-in period, an open 10-week dose-adjustment period, and finally a 14-week maintenance period. Of the 39 efficacy-evaluable patients, 25 (64%) achieved adequate blood pressure control (diastolic blood pressure less than 90 mm Hg or a decrease in diastolic blood pressure greater than 10 mm Hg) at a mean daily dose of 2 mg of doxazosin. No persistent changes occurred in heart rate. In the 32 patients with evaluable lipid data, there were nonsignificant trends to an increase in high-density lipoprotein cholesterol and a reduction in total cholesterol, together with a significant reduction in serum triglyceride concentration. The combined changes in blood pressure and blood lipid levels resulted in a reduction of 36% in the calculated risk of coronary heart disease. Eleven patients reported side effects and four were withdrawn from therapy. These results confirm the antihypertensive and anticholesterolemic efficacy of once-daily treatment with doxazosin.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha-adrenergic blockers: mechanism of action, blood pressure control, and effects of lipoprotein metabolism

The sympathetic nervous system plays a major role in the pathogenesis of essential hypertension and is mediated by the alpha and beta receptors. The alpha receptor is divided into two types, alpha 1 and alpha 2, based on response to epinephrine and norepinephrine. alpha 1-Adrenergic receptors have a high affinity for drugs such as prazosin, doxazosin, and terazosin, which act to reduce blood pressure by selective blockade of the receptor. These agents provide a rational approach to the treatment of hypertension by correcting elevated total peripheral resistance, the fundamental hemodynamic abnormality in essential hypertension. In contrast, early alpha-adrenergic receptor blockers nonselectively blocked both alpha 1 and alpha 2 receptors and were unsuitable as antihypertensive agents because they induced tachycardia and patients developed a tolerance to them rapidly. alpha 1-Adrenergic blockers also have beneficial effects on plasma lipoproteins, tending to decrease levels of triglycerides and cholesterol and increase levels of high-density lipoprotein (HDL) cholesterol and the HDL cholesterol/total cholesterol ratio. beta-Adrenergic blockers, such as propranolol and atenolol, have been shown to have an adverse effect on the lipid profile by tending to increase levels of triglycerides and decrease HDL cholesterol. A number of mechanisms contribute to these effects, in particular, adrenergic modulation of lipoprotein lipase and the triglyceride secretion rate. Doxazosin has been shown to increase the activity of LDL receptors, which may be partly responsible for its beneficial effect on plasma lipids and lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacotherapeutics of doxazosin

Doxazosin is the latest in a series of highly selective postsynaptic alpha 1-adrenoceptor inhibitors. It is readily absorbed, with high bioavailability and a relatively long plasma half-life, neither of which property is influenced by age. This accounts for the prolonged pharmacologic activity of doxazosin following a single oral dose. Its prime pharmacodynamic activity resides in its ability to counter sympathetic vasoconstriction of the systemic arteriolar resistance vessels and venous capacitance system, which enables the drug to target the major pathophysiologic abnormality in hypertension, i.e., the generalized systemic arteriolar constriction. The widespread vasodilation induced by doxazosin relieves both cardiac preload and afterload and, consequently, reduces left ventricular wall stress and myocardial oxygen consumption. In hypertension, doxazosin reduces blood pressure both at rest and during exercise by reduction of systemic vascular resistance without precipitating substantial reflex cardiac stimulation. The effects are maximal on the standing blood pressure between two and four hours after ingestion; due to doxazosin's relatively slow absorption, postural hypotension is infrequent. Its antihypertensive activity is maintained over 24 hours following a single oral dose, and the optimal dose range is 2 to 8 mg once daily. The antihypertensive efficacy of doxazosin has been shown to be comparable with that of other alpha-adrenoceptor inhibitors, beta-blocking drugs, diuretics, calcium antagonists, and angiotensin-converting enzyme inhibitors. In contrast to other conventional antihypertensive drugs, a unique feature of alpha-adrenoceptor-inhibiting drugs, including doxazosin, is their ability to reduce the plasma concentrations of triglycerides, total cholesterol, and low-density lipoprotein cholesterol and to increase high-density lipoprotein cholesterol concentration. This contrasts with the opposite effect on lipid levels induced by hydrochlorothiazide and atenolol seen in comparative studies. Side effects show no predilection for any organ system, and the overall incidence of such effects compares well with those of other commonly used antihypertensive drugs. This unique combination of antihypertensive efficacy and favorable effect on blood lipid levels indicates that once-daily treatment with doxazosin holds considerable promise in the treatment of hypertension, both from the point of view of its antihypertensive efficacy and also from its primary preventative potential.