Plasma lipid lowering effects of doxazosin, a new selective alpha1 adrenergic inhibitor for systemic hypertension

Direct Vasodilators and Sympatholytic Agents

Direct vasodilators and sympatholytic agents were some of the first antihypertensive medications discovered and utilized in the past century. However, side effect profiles and the advent of newer antihypertensive drug classes have reduced the use of these agents in recent decades. Outcome data and large randomized trials supporting the efficacy of these medications are limited; however, in general the blood pressure-lowering effect of these agents has repeatedly been shown to be comparable to other more contemporary drug classes. Nevertheless, a landmark hypertension trial found a negative outcome with a doxazosin-based regimen compared to a chlorthalidone-based regimen, leading to the removal of α-1 adrenergic receptor blockers as first-line monotherapy from the hypertension guidelines. In contemporary practice, direct vasodilators and sympatholytic agents, particularly hydralazine and clonidine, are often utilized in refractory hypertension. Hydralazine and minoxidil may also be useful alternatives for patients with renal dysfunction, and both hydralazine and methyldopa are considered first line for the treatment of hypertension in pregnancy. Hydralazine has also found widespread use for the treatment of systolic heart failure in combination with isosorbide dinitrate (ISDN). The data to support use of this combination in African Americans with heart failure are particularly robust. Hydralazine with ISDN may also serve as an alternative for patients with an intolerance to angiotensin antagonists. Given these niche indications, vasodilators and sympatholytics are still useful in clinical practice; therefore, it is prudent to understand the existing data regarding efficacy and the safe use of these medications.

ATP-Binding Cassette Transporter A1 Gene Transcription Is Downregulated by Activator Protein 2α

ATP-binding cassette transporter A1 (ABCA1) is a rate-limiting factor for high-density lipoprotein (HDL) biogenesis. The ABCA1 gene expression is known to be upregulated by various transcriptional factors. However, negative regulation factors would be better targets for pharmacological modulation of HDL biogenesis. Doxazosin, an α 1 -adrenoceptor blocker, increased ABCA1 mRNA, its protein, and apolipoprotein A-I–mediated HDL biogenesis in THP-1 macrophages and CHO-K1 cells, independent of α 1 -adrenoceptor blockade. Analysis of the human ABCA1 promoter indicated that the region between the positions −368 and −147 that contains an activator protein (AP)2-binding site responsible for the effects of doxazosin. Overexpression of AP2α inhibited ABCA1 transcription in a dose-dependent fashion. Mutation in the AP2-binding site caused increase of the basal promoter activity and canceling both the transactivation by doxazosin and the trans-repression by AP2α. Doxazosin had no effect on ABCA1 mRNA level in HepG2 cells, which lack endogenous AP2α, and it reversed the inhibitory effect of AP2α expression in this type of cells. Chromatin immunoprecipitation and gel shift assays revealed that doxazosin reduced specific binding of AP2α to the ABCA1 promoter, as it suppressed phosphorylation of AP2α. Finally, doxazosin increased ABCA1 expression and plasma HDL in mice. We thus concluded that AP2α negatively regulates the ABCA1 gene transcription. Doxazosin inhibits AP2α activity independent of α 1 -adrenoceptor blockade and increases the ABCA1 expression and HDL biogenesis. AP2α is a potent pharmacological target for the increase of HDL.

Controlled-release doxazosin in the treatment of benign prostatic hyperplasia

PURPOSE

To evaluate the effectiveness and safety of controlled-release doxazosin for benign prostatic hyperplasia (BPH).

SCOPE

In this open-label, noncontrolled, observational surveillance study, 3684 men with BPH received 4-8 mg of controlled-release doxazosin gastrointestinal therapeutic system (GITS) for 6 months; 3283 (89.1%) patients completed the trial. Changes in urinary symptoms and quality of life were assessed using the International Prostate Symptom Score (IPSS). Blood pressure and adverse events were assessed.

CONCLUSION

After 6 months' treatment with doxazosin GITS resulted in significant improvements in IPSS. BP was reduced only in hypertensive patients. Doxazosin, GITS was well tolerated.

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.

Efficacy and tolerability of doxazosin versus enalapril in the treatment of patients with mild-to-moderate hypertension

The effects of 4 weeks of treatment with doxazosin or enalapril on diastolic blood pressure (DBP) and plasma lipid levels were studied in 160 patients 18 to 50 years old with mild-to-moderate hypertension. Comparing baseline measurements with measurements taken after 4 weeks, DBP was significantly reduced by 6.8 +/- 7.4 (mean +/- SD) mm Hg and 12.0 +/- 7.1 mm Hg in the doxazosin and enalapril groups, respectively. Systolic blood pressure was significantly decreased from baseline to end of treatment in both groups. There were no significant changes in heart rate from baseline to end of treatment in the doxazosin group, but there was a statistically significant decrease in heart rate in the enalapril group. High-density lipoprotein cholesterol increased statistically significantly in the doxazosin group but not in the enalapril group. A decrease in triglycerides was statistically significant with respect to the doxazosin group and was close to significance for the enalapril group. Forty-nine (62%) patients in the doxazosin group and 43 (54%) patients in the enalapril group reported at least one adverse event. Significant reductions in DBP after 4 weeks of treatment were achieved by both drugs, each taken once daily. This reduction was more pronounced in the enalapril group 24 hours postdose, with a mean final daily dose of 2.8 mg of doxazosin and 12.6 mg of enalapril. However, even relatively short-term treatment with low-dose doxazosin showed a more favorable effect on lipids than did enalapril.

Review: the effects of antihypertensive agents on serum lipids

Because various antihypertensive drugs adversely affect lipid metabolism, these drugs may increase associated risks for coronary artery disease and thus offset some of the beneficial effects of blood pressure reduction. In this paper the current literature regarding the effects of antihypertensive agents on serum lipids is reviewed. Differing effects of various classes of antihypertensives are assessed to further our understanding of this very important subject.

Preservation of endothelium-dependent vascular relaxation in cholesterol-fed mice by the chronic administration of prazosin or pravastatin

The relaxation of aortic rings in response to acetylcholine (ACh) was significantly decreased in cholesterol-fed mice. The attenuated relaxation in cholesterol-fed mice was preserved by the chronic administration of prazosin (20 mg/kg/day) or pravastatin (12.5 mg/kg/day). Serum low-density lipoprotein (LDL) levels were significantly increased in mice given cholesterol. The increased serum LDL levels in cholesterol-fed mice were returned to normal by the chronic administration of prazosin and pravastatin. A prior incubation of aortic rings with lysophosphatidylcholine (LPC) significantly attenuated ACh- and A23187-induced endothelium-dependent relaxation. The inhibitory effects of LPC on endothelium-dependent relaxation were not affected by indomethacin or superoxide dismutase. The sodium nitroprusside-induced relaxation of aortic rings was not changed by LPC. The inhibitory effects on ACh-induced relaxation by NG-monomethyl-L-arginine were restored by a prior exposure to L-arginine, whereas the inhibition of endothelium-dependent relaxation by LPC was not affected by L-arginine. These results suggest that cholesterol-fed mice are useful animal models of hypercholesterolemia, and chronic administration of prazosin or pravastatin can preserve endothelium-dependent relaxation by lowering serum LDL in these animals. It is further suggested that LPC derived from oxidized LDL may be involved in the reduced endothelium-dependent relaxation in hyperlipidemia.

Comparative and combined efficacy of doxazosin and enalapril in hypertensive patients

Twenty patients with essential hypertension were randomised to a 7-week period of dose titration with doxazosin, 1-8mg/day or enalapril, 5-20mg/day. In a further 7-week period the dosage level reached with the initial drug was halved, and titration with the second agent was carried out. Blood pressure responses at the end of each treatment period were assessed by clinic measurements made 24 hours post-dose. In the first treatment period, enalapril (mean dose 19mg/day) reduced serum free ACE activity by 40% and had a greater effect than doxazosin (mean dose 5.2mg/day) on clinic supine blood pressure (systolic and diastolic). In the second period, the addition of enalapril to doxazosin was associated with a significant fall in clinic standing blood pressure (systolic and diastolic), despite the doxazosin dose reduction and consequent decrease in median plasma doxazosin concentration (from 10.6 to 5.2ng/ml). Alternatively, when doxazosin was added to enalapril, free ACE activity remained 40% decreased despite enalapril dose reduction, and blood pressure was not further affected. Plasma renin activity was increased by enalapril. No changes were observed in plasma aldosterone or lipid concentrations with either drug. The combination of doxazosin and enalapril was well tolerated and lowered blood pressure overall. Judged by clinic measurements 24 hours post-dose, most of the antihypertensive effect was attributable to the enalapril component. However, ambulatory blood pressure monitoring 0-12 hours post-dose in a subset of patients suggested a contribution of doxazosin earlier in the dose interval.

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.

The place of alpha blockers in the antihypertensive armamentarium

Although beta-blockers and diuretics are presently the only medications shown to reduce morbidity and mortality in hypertensives in large clinical trials, these drugs have not exerted optimal expected benefits in reducing cardiac events. Alpha-1 selective blockers exhibit a favorable impact on lipids, particularly on HDL-cholesterol. Unlike beta-blockers, they do not increase triglycerides and they do not produce the increase in LDL-cholesterol observed with traditional doses of diuretics. Alpha-blockers should be considered in the treatment of hypertensives with lipid disorders or diabetes and in those who have contraindications, failure to respond or toxicity associated with diuretics and/or beta-blockade.

Mechanisms of action of adrenergic receptor blockers on lipids during antihypertensive drug treatment

The objective of this article is to focus on the antihypertensive agents blocking adrenergic receptors, both alpha and beta blockers, and attempt to construct potential explanations for their effects on lipids in a mechanistic manner. The essential thesis is that adrenergic control of lipid metabolism is responsible for the effect on lipids and lipoproteins of antihypertensive agents that block adrenergic receptors. Agonists and antagonists show the opposite action on lipoprotein lipase, lecithin:cholesterol acyltransferase (LCAT) and LDL-cholesterol uptake by LDL receptors in a manner that might explain the findings of increases in triglycerides and LDL cholesterol with decreases in HDL cholesterol in patients receiving beta blockers without intrinsic sympathomimetic activity and the reverse in patients on treatment with alpha adrenergic receptor blockers.

Comparative trial of doxazosin and atenolol on cardiovascular risk reduction in systemic hypertension. The Alpha Beta Canada Trial Group

The impact of treating hypertension on coronary artery disease has been less than anticipated from epidemiologic studies of cardiovascular risk factors. It has been suggested that adverse effects on lipids of traditional diuretic or beta-blocker regimens may diminish the potential benefits of antihypertensive therapy. Patients with mild to moderate systemic hypertension and normal serum lipids (n = 191) were randomly assigned to doxazosin or atenolol. After dose titration to goal diastolic blood pressure of < or = 90 mm Hg, patients continued treatment for a further 24 weeks. The principal outcome measurement was overall coronary artery disease risk using the Framingham formula. Relative risk of coronary artery disease was reduced to 92.4% of baseline (p = 0.144) for evaluable patients taking atenolol (n = 71), and to 74.6% (p = 0.0001) for patients taking doxazosin (n = 51): atenolol versus doxazosin, p = 0.0074. In patients who met the strict Framingham criteria for age, total cholesterol and high density lipoprotein cholesterol, the relative risk of coronary artery disease for patients taking atenolol (n = 23) was reduced to 86.2% of baseline (p = 0.082), and to 67.4% (p = 0.0004) for patients taking doxazosin (n = 18): atenolol versus doxazosin, p = 0.049. Alpha blockade with doxazosin was more effective than beta blockade with atenolol in reducing the risk of coronary artery disease in hypertensive patients because of the beneficial effects of doxazosin on high-density lipoprotein cholesterol. Overall withdrawal rate was greater in the alpha-blocker group because of a lower response rate and more adverse events.

Doxazosin in the treatment of essential hypertension in general medical practice in Latin America

This Latin American study assessed in the general practice setting the efficacy and tolerance of once-daily doxazosin in the treatment of mild or moderate essential hypertension (sitting diastolic blood pressure, 95 to 115 mm Hg). Patients (n = 220) were treated with doxazosin for 12 weeks as monotherapy or in combination with other antihypertensive agents. At the final visit, doxazosin produced a mean change in sitting systolic/diastolic blood pressure of -18.4/-14.4 mm Hg, at a mean daily dose of 4.3 mg. One hundred sixty-three (77.6%) of the 210 evaluable patients were considered a therapeutic success. Lipid analyses identified a statistically significant (p = 0.02) reduction in total serum cholesterol (4.85%) and an overall decrease in triglyceride levels (5.12%). According to the Framingham Heart Study equation, doxazosin produced a highly significant (p less than 0.001) 20% reduction in the calculated probability of developing coronary heart disease in 10 years. Of the 220 patients evaluated, 54 (24.5%) reported side effects that were considered related to treatment. Ten (4.5%) patients reported side effects unrelated to treatment and 37 (16.8%) reported events of unknown relationship. Most side effects were mild or moderate and were tolerated or disappeared with continued treatment. Nine patients (4.1%) were discontinued from therapy and in 13 (5.9%) the dose was reduced. The most prevalent side effects were headache and dizziness. The investigator's overall assessment of antihypertensive efficacy was excellent or good for 176 patients (80.4%); tolerance was considered excellent or good in 193 patients (88.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Doxazosin in the treatment of mild or moderate essential hypertension: an echocardiographic study

Sixteen patients with mild or moderate essential hypertension received 1 to 8 mg/day of doxazosin (mean daily dose, 2.7 mg). Blood pressure reduction (supine and standing) was highly significant (p less than 0.001), and no significant changes in heart rate were observed. A significant reduction (p less than 0.01) in left ventricular mass was seen without a change in left ventricular systolic function. All side effects were mild, and only one patient withdrew from the study.

Effects of doxazosin on serum lipids: a review of the clinical data and molecular basis for altered lipid metabolism

The goal of antihypertensive treatment must be not only the reduction of high blood pressure, but also the effective management of elevated cholesterol levels and other risk factors of coronary heart disease (CHD). In controlled clinical trials, doxazosin has been shown to have antihypertensive efficacy comparable with other classes of antihypertensive agents and to lower the levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides while increasing the levels of high-density lipoprotein cholesterol. Doxazosin appears to inhibit the development of CHD on two fronts. First, doxazosin binds to the alpha 1-adrenoreceptor and inhibits the receptor-mediated responses to epinephrine and norepinephrine. Second, doxazosin has direct and indirect effects on lipid metabolism by increasing LDL receptor activity, decreasing intracellular LDL synthesis, reducing the synthesis and secretion of very low-density lipoprotein cholesterol, and stimulating lipoprotein lipase activity. Doxazosin may also inhibit platelet aggregation. Long-term studies will determine how these actions translate into reductions in the morbidity and mortality rates of CHD. First-year results from the Treatment of Mild Hypertension Study (TOMHS) have demonstrated expected reductions in blood pressure for all antihypertensive agents studied. The lipid changes have varied with the type of antihypertensive treatment and have been favorable for doxazosin.

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)

Evidence of an antiplatelet aggregation action of doxazosin in patients with hypertension: an ex vivo study

Eighteen patients with a mean age of 54.7 years were included in the study. All patients had a diagnosis of mild or moderate essential hypertension (sitting diastolic blood pressure of 96 to 114 mm Hg). The study design was single blind and in two phases: phase I, placebo (4 weeks), and phase II, the active treatment (8 weeks) with increasing doses, if needed, of doxazosin every 2 weeks (1, 2, 4, and 8 mg/day). Results show that doxazosin has an antihypertensive effect that is dose dependent. Systolic, diastolic, and mean blood pressures were decreased significantly, and no effect on heart rate was observed. Doxazosin significantly inhibited the platelet aggregation induced by epinephrine, adenosine diphosphate, and collagen in a dose-dependent manner. In addition, treatment with doxazosin lowered total serum cholesterol and triglyceride levels, without changing other standard biochemical parameters. This indicates that doxazosin could offer a distinct therapeutic advantage in the modulation of atherogenic and thromboembolic factors associated with coronary heart disease.

Clinical experience with doxazosin in general medical practice in New Zealand

This study investigated the safety and efficacy of doxazosin treatment in a large population of patients (n = 336) with essential hypertension and assessed the effect of doxazosin on the serum lipid profile and the calculated risk of developing coronary heart disease. Patients were assigned to two groups: those with a baseline diastolic blood pressure greater than or equal to 95 mm Hg (group 1) and those with a baseline diastolic blood pressure less than 95 mm Hg (group 2) that was controlled by previous antihypertensive therapy. Doxazosin treatment (monotherapy in 76.2% of patients) significantly (p less than 0.05) reduced the blood pressure of patients in group 1 (-23/-17 mm Hg) after 10 weeks and maintained the control of blood pressure for patients in group 2. Heart rate was essentially unchanged in both groups. Mean final daily doses of 3.6 and 3.2 mg were achieved in groups 1 and 2, respectively. Treatment with doxazosin improved the severity category of hypertension for 88.4% of patients in group 1; 87.3% of patients were considered a therapy success. Doxazosin had a favorable effect on the serum lipid profile in both groups of patients. The majority of lipid changes achieved statistical significance and resulted in a significant 27% decrease in the calculated risk of developing coronary heart disease. Doxazosin was well tolerated; only 24.1% of patients had side effects that were related or possibly related to treatment. In nine (2.7%) patients the dose of doxazosin was reduced and 26 (7.7%) patients withdrew from doxazosin therapy because of side effects.

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)

The cost-benefit approach to pricing new medicines: doxazosin versus beta-blocker treatment in Sweden

The economic evaluation of pharmaceuticals is becoming increasingly important. This article presents an illustrative example of how the cost-benefit approach can be used in the pricing of a new pharmaceutical product. Doxazosin, a new selective alpha 1-inhibitor used in the treatment of hypertension, is compared with the established beta-blocker, atenolol. Cost-effectiveness ratios are calculated for both, and from the analysis it emerges that doxazosin is the more cost-effective agent. This is largely the result of the favorable high-density lipoprotein/total cholesterol changes that doxazosin produces. Even when doxazosin is priced 30% higher than atenolol, doxazosin is more cost-effective. It is concluded that in the future economic evaluations will have significant impacts on research and development within the pharmaceutical industry. However, a number of issues still must be addressed, and economic evaluation should be subject to continuous review.

Review of the effects of doxazosin, a new selective alpha 1-adrenergic inhibitor, on lipoproteins in patients with essential hypertension

Control of high blood pressure has failed to reduce the risk of atherosclerotic coronary heart disease (CHD). Hypercholesterolemia, which is common among hypertensive patients, cigarette smoking, and hypertension are the major risk factors for CHD. To minimize CHD risk, elevated blood pressure and atherogenic lipid levels should be lowered, but various antihypertensive agents appear to adversely affect lipid levels, actually precluding the CHD risk reduction expected from blood pressure control. Doxazosin, a once-daily, long-acting, alpha 1-adrenergic inhibitor, not only is effective therapy for essential hypertension but also has a favorable impact on lipids. During controlled studies of doxazosin's antihypertensive efficacy, the following blood lipid levels were measured: total cholesterol, total triglycerides, high-density lipoprotein (HDL) cholesterol (including HDL2 and HDL3), low-density lipoprotein (LDL) cholesterol, very low-density lipoprotein cholesterol, and apoproteins (apos) AI and B. Results showed total cholesterol (-0.8 to -8.9 percent), total triglycerides (-5.0 to -17.4 percent), and LDL (-9.0 to -16.9 percent) were reduced. The positive prognostic indicators, HDL (+0.7 to +13.0 percent) and HDL:total cholesterol ratio (+3.1 to +26.3 percent), were increased. Apo B decreased, but apo AI remained unchanged. In these hypertension studies, doxazosin has favorably reduced two major CHD risk factors. As part of a new, long-term, controlled, multicenter trial, the prospective benefits of these risk factor reductions on CHD morbidity and mortality will be quantified for doxazosin and other antihypertensive agents.

Management of hypertension. Potential trade-offs on coronary risk

The major risk factors for coronary heart disease remain high blood pressure, cigarette smoking, and abnormal serum lipid levels, including total cholesterol but more specifically elevated low-density lipoprotein cholesterol and reduced high-density lipoprotein cholesterol levels. Observations made from large-scale trials almost a decade ago suggested that commonly used antihypertensive agents, such as thiazide diuretics and beta-blockers, may adversely influence serum lipid levels. Over time, we realized that these lipid alterations persist long term and are of sufficient magnitude to potentially account for important differences in coronary heart disease risk reduction among various antihypertensive drug regimens. Considering recent National Cholesterol Education Program and Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure recommendations concerning lipid and blood pressure treatment, it is prudent and timely to rethink our approach to antihypertensive therapy in patients with abnormal serum lipid levels. Therefore, when lipids are a concern, appropriate dietary treatments should be advised and antihypertensive therapy that has a beneficial or neutral impact on serum lipid levels should be considered.

alpha 1-antagonists in the treatment of hypertension

A number of agents are now available to treat hypertension. One relatively new class of agents is the selective alpha 1-inhibitors, which have distinct advantages over earlier nonselective alpha-adrenergic receptor-blocking agents. Three alpha 1-inhibitors are reviewed in this article: prazosin, terazosin, and doxazosin. These alpha 1-inhibitors are similar in chemical structure and pharmacological action. alpha 1-Inhibitors lower blood pressure by reducing vascular tone in resistance and capacitance vessels. alpha 1-Inhibitors are similar in effectiveness in blood pressure lowering to other commonly used antihypertensive agents like the thiazide diuretic drugs and beta-blockers, which are efficacious as monotherapy in lowering pressure, as initial agents, or in combination with other antihypertensive agents in multidrug therapeutic regimens. alpha 1-Inhibitors are associated with a reasonably low incidence of serious adverse effects and are essentially free of any adverse metabolic effects. alpha 1-Inhibitors have been shown to beneficially effect blood lipids in several studies. The favorable lipid effect makes alpha 1-inhibitors especially appropriate to use in diabetic hypertensive and other patients with elevated serum lipid levels. The beneficial lipid effects may enhance the ability of alpha 1-inhibitors to prevent coronary heart disease, an outcome that has been difficult to demonstrate in thiazide-based trials.

Hypertension

An estimated 58 million Americans are at increased risk of morbidity and premature death due to high blood pressure (BP) and require some type of therapy or systematic monitoring. This article focuses on recent advances in our understanding of the pathogenesis of hypertension, new approaches to the diagnosis and treatment of secondary hypertension, and current views of the most appropriate nonpharmacologic and pharmacologic therapy for essential hypertension. In view of the extremely high prevalence of the disorder, emphasis is placed on efficient and cost-effective strategies for diagnosing and managing the hypertensive patient. Recent evidence indicates that nonpharmacologic therapy, including dietary potassium and calcium supplements, reduction of salt intake, weight loss for the obese patient, regular exercise, a diet high in fiber and low in cholesterol and saturated fats, smoking cessation, and moderation of alcohol consumption produces significant sustained reductions in BP while reducing overall cardiovascular risk. Accordingly, nonpharmacologic antihypertensive therapy should be included in the treatment of all hypertensive patients. In persons with mild hypertension, nonpharmacologic approaches may adequately reduce BP, thereby avoiding the expense and potential side effects of drug therapy. In patients with more severe hypertension, nonpharmacologic therapy, used in conjunction with pharmacologic therapy, can reduce the dosage of antihypertensive medications necessary for BP control. Patients treated with nonpharmacologic therapy only should be followed closely, and if BP control is not satisfactory, drug therapy should be added. The large number of drugs available for use in hypertension treatment, coupled with our rapidly expanding knowledge of the pathophysiology of hypertension and of the adverse effects of these drugs in individual patient groups, make it possible to individualize antihypertensive treatment. When used as monotherapy, most agents effectively lower BP in the majority of patients with mild or moderate essential hypertension. Thus, a single agent from one of four classes: diuretics, angiotensin-converting enzyme inhibitors, calcium channel blockers, and beta-adrenergic blockers, usually provides effective BP control with minimal side effects in most patients. Therapy should be initiated with the agent most likely to be effective in BP lowering and best tolerated. If the initial agent is ineffective at maximal recommended therapeutic doses or has undue side effects, an alternative agent from another class should be tried. When monotherapy is unsuccessful, a second agent, usually of a different mechanism of action, should be

The relevance of plasma lipid changes with cardiovascular drug therapy

Evidence is reviewed that thiazide diuretics increase plasma levels of triglycerides and LDL-cholesterol, and that most beta-blockers increase triglycerides and depress HDL-cholesterol. By contrast, indapamide, pindolol, and calcium channel blockers have little effect, and alpha 1-blockers and alpha 2-stimulants may improve the HDL- to LDL-cholesterol ratio.

Mechanism of the interaction of hypertension and hypercholesterolemia in atherogenesis: the effects of antihypertensive agents

Any alteration in the balance between serum lipids, platelets, hemodynamic factors, and the blood vessel wall may lead to the development of atherosclerosis. Hypertension and hypercholesterolemia are two major risk factors that accelerate the development of coronary heart disease. The mechanisms of the interactions of these two risk factors are examined in this paper. First, hypertension may be associated with focal or generalized endothelial injury or dysfunction. The altered endothelial functional integrity may predispose to platelet aggregation and altered vessel wall interaction, which may stimulate proliferation and growth of vascular cells. Second, elevated serum cholesterol levels may accelerate lipid deposition and formation of atherosclerotic plaques. In hypertension the rate of clearance of lipoprotein from the vessel wall may be reduced. Third, the sympathetic nervous system may be involved in both the development of hypertension and the alterations of lipid metabolism. Adrenergic activation, which increases blood pressure may also adversely affect lipid metabolism. This is in part alpha 1-adrenoceptor mediated. Selective alpha 1-inhibitors have been found to prevent or reduce atherosclerosis in experimental animals. Selective alpha 1-inhibitors may act at a number of sites on lipoprotein metabolic pathways to favorably influence serum lipids. Taken together, the relationship between hypertension and atherosclerosis involves complex mechanisms. A complete understanding of the mechanisms is of obvious importance.

Doxazosin versus atenolol: a randomized comparison of calculated coronary heart disease risk reduction

Doxazosin is a selective alpha 1-inhibitor for the reduction of calculated coronary heart disease (CHD) risk in hypertensive patients. Atenolol, although a widely used beta-blocker, appears to adversely affect blood lipids by increasing triglycerides and decreasing high-density lipoprotein (HDL) cholesterol. The aim of our study was to compare doxazosin and atenolol for their therapeutic efficacy in reducing CHD risk (decrease in blood pressure and effect on lipid distribution) and toleration. Patients with mild-to-moderate hypertension were randomized into two groups of 20 patients to receive once-daily atenolol (100 mg) or doxazosin (2 to 8 mg) for 8 weeks. Doxazosin was as effective as atenolol in reducing supine and standing blood pressure. Unlike atenolol, doxazosin did not produce a marked bradycardia. Doxazosin therapy produced favorable modifications in plasma lipid profiles by decreasing triglycerides and total cholesterol and by increasing HDL cholesterol and HDL/total cholesterol ratio. A reverse in this lipid profile was seen with atenolol. Therefore doxazosin may reduce calculated CHD risk more effectively than atenolol, based on the Framingham equation.

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

The efficacy and toleration of doxazosin and atenolol were compared over a 52-week period in a double-blind, multicenter study of 228 patients with mild-to-moderate hypertension. Over the treatment period, both drugs significantly reduced blood pressure, and there were no clinically or statistically significant differences between treatment groups for reductions in standing systolic and diastolic blood pressures or in sitting diastolic blood pressure. However, atenolol treatment caused significantly greater reductions in sitting systolic blood pressure and heart rate. Neither drug significantly affected total serum cholesterol concentrations. Doxazosin treatment lowered serum triglycerides, whereas atenolol treatment produced an increase in serum triglycerides (p less than 0.001, week 30; p less than 0.01, week 50, between treatment groups). Increases in high-density lipoprotein cholesterol and high-density lipoprotein to total cholesterol ratio were obtained with doxazosin treatment, whereas atenolol treatment decreased these lipid fractions (p less than 0.0001, weeks 30 and 50, between treatment groups). Using the Framingham equation, it was calculated that at week 50 the risk of developing coronary heart disease was reduced by 22% for the group taking doxazosin (p less than 0.001 vs baseline) and by 4% (not significant) for patients taking atenolol (p = 0.01, between treatment groups). It is concluded that doxazosin is a well-tolerated and effective antihypertensive drug with a favorable effect on blood lipids. Doxazosin provides an attractive, new alternative first-line drug for the treatment of mild-to-moderate hypertension.

Implications of doxazosin therapy on risk of coronary heart disease

Antihypertensive treatment is known to reduce mortality in severe hypertension and cardiovascular morbidity in mild and moderately severe hypertension, for example, from stroke and left ventricular failure. However, treated hypertensive patients still have significantly higher mortality and morbidity than matched control subjects. In particular, risk of coronary heart disease is affected little by antihypertensive treatment. There may be several explanations for these less than optimal results. For example, blood pressure may not have been brought down to strictly normotensive levels or an antihypertensive agent, which adversely affects serum lipoproteins, may have been used, thereby offsetting the intended therapeutic effect. Doxazosin, a new selective alpha 1-inhibitor, offers both effective antihypertensive action and a favorable lipid effect. Both of these effects could have a positive impact on risk of coronary heart disease and therefore may prove to be more effective than previously used antihypertensive treatments.

A double-blind comparative study of doxazosin and nitrendipine in patients with mild-to-moderate essential hypertension

The antihypertensive efficacy and safety of doxazosin, a selective alpha 1-inhibitor, were compared with nitrendipine. Seventy-two hypertensive patients were entered into the 18-week, double-blind parallel group study, which involved three phases: a 4-week baseline period, a 10-week period in which patients received 1 to 8 mg of doxazosin or 10 and 20 mg of nitrendipine once daily, and a 4-week maintenance period. For all patients, the mean final daily doses were 2.5 mg for doxazosin and 13.9 mg for nitrendipine. In efficacy evaluable patients the percentages of therapy successes (standing diastolic blood pressure less than or equal to 90 mm Hg with greater than or equal to 5 mm Hg reduction or greater than or equal to 10 mm Hg decrease) were comparable for doxazosin (94%) and nitrendipine (91%), as was the proportion in whom blood pressure was "normalized" (standing diastolic blood pressure less than or equal to 90 mm Hg), 91% and 85, respectively. Blood pressures (diastolic and systolic in supine and standing positions) were significantly reduced (p less than 0.05) at all visits in both treatment groups. Ten patients (28%) in each treatment group experienced at least one adverse event. No clinically significant laboratory changes were apparent in either the doxazosin or nitrendipine groups, and no trends were observed with regard to organ systems or correlations with dose or duration of treatments. The investigators' global assessment of efficacy was rated excellent or good for all doxazosin-treated patients and excellent or good for 32 and fair for four in the nitrendipine group.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of major intervention studies in hypertension and hyperlipidemia: focus on coronary heart disease

The ultimate aim in treating hypertension and hyperlipidemia is to reduce cardiovascular mortality and morbidity, especially strokes and coronary events, for example, fatal and nonfatal myocardial infarction and sudden death. Extensive intervention studies in moderate-to-severe hypertension have revealed the significance of antihypertensive therapy in reducing total cardiovascular mortality and morbidity, particularly from cerebrovascular causes. However, the reduction of coronary events has not been equally successful. The situation in mild-to-moderate hypertension is even more disappointing: recent studies, such as the Medical Research Council hypertension trial, the international Prospective Primary Prevention Study in Hypertension, and the Heart Attack Primary Prevention in Hypertensives trial could not demonstrate any benefit from antihypertensive treatment with beta-blockers or diuretics in the prevention of coronary heart disease. The reasons for these negative results are not obvious. However, metabolic side effects associated with certain antihypertensive drugs, which counteract the beneficial effects of blood pressure reduction, are one topic of discussion. For the genesis of atherosclerosis of the coronary vasculature, hyperlipoproteinemia appears to be of greater importance than hypertension and has to be treated simultaneously. Two extensive intervention studies, the Lipid Research Clinics coronary primary prevention trial and the Helsinki Heart Study, showed a significant reduction of coronary events with lipid-lowering treatments with cholestyramine and gemfibrozil, respectively. These findings are in agreement with the results of a recent secondary prevention study, which showed a regression of atherosclerosis in coronary arteries and aortocoronary bypass grafts. Moreover, antihypertensive treatment aimed at a reduction in coronary heart disease has to focus on serum lipids, especially in mild hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative study of doxazosin versus atenolol in mild-to-moderate hypertension

Doxazosin, a quinazoline derivative, is a selective alpha 1-inhibitor that reduces calculated coronary heart disease risk by lowering blood pressure while favorably affecting blood lipid levels. The aim of this study was to compare the efficacy and toleration of doxazosin with atenolol, one of the most frequently used cardioselective beta-blockers in Italy. Forty patients with mild-to-moderate hypertension were treated with either atenolol (100 mg) or doxazosin (mean dose, 3.3 mg) once daily for 8 weeks. Both drugs significantly reduced supine and standing systolic and diastolic blood pressures. Atenolol induced marked bradycardia, whereas doxazosin had very little effect on heart rate. Doxazosin produced a favorable effect on blood lipid levels by decreasing triglyceride and total cholesterol levels and increasing high-density lipoprotein cholesterol and high-density lipoprotein total cholesterol ratio. Atenolol had exactly the opposite effect on blood lipid levels. Both drugs had equivalent toleration profiles. It was concluded that doxazosin was as effective as atenolol in reducing elevated supine and standing blood pressures. In addition, doxazosin had a beneficial effect on lipid profiles and minimal effect on heart rate. Therefore doxazosin may reduce calculated coronary heart disease risk in hypertensive patients.

Effects of doxazosin on diet-induced hypercholesterolemia in C57BR/cdJ mice

Plasma cholesterol levels are markedly reduced when doxazosin, a selective alpha 1-adrenoceptor inhibitor, is administered for several days to C57BR/cdJ mice that have been fed a high cholesterol diet. This system affords a useful model for investigating the mechanism by which selective alpha 1-adrenoceptor inhibitors decrease circulating lipid levels. The results indirectly suggest that hypercholesterolemia induced by dietary cholesterol may involve activation of the sympathetic nervous system. The basis for linkage between circulating cholesterol levels and sympathetic nervous activity, while not yet understood, may involve changes in the balance among cholesterol pathways in the liver, alteration of vasomotor tone and control of the activity of vascular endothelial lipases. An additive effect is described for cholestyramine and doxazosin, in which low density lipoprotein cholesterol is decreased by 76% by a combination of maximal doses of the 2 agents.

Coronary artery disease risk factor management in the hypertensive patient

Recent advances in understanding the relation of risk factors to coronary artery disease (CAD) have initiated a change in the approach to managing the hypertensive patient. Reduction of elevated blood pressure still remains a major therapeutic priority. However, the risk of cardiovascular morbidity is also related to hypercholesterolemia, hyperuricemia, hyperglycemia, hyperfibrinogenemia and obesity; all aggravate the risk of CAD in the patient with high blood pressure. Life-style is also important: cigarette smoking, high alcohol consumption and lack of physical exercise all predispose to precocious atheromatous CAD. Thus, the most favorable prognosis in terms of reducing CAD risk is accomplished by reducing elevated systemic arterial pressure while simultaneously improving all other risk factors. The method by which blood pressure is lowered is an important consideration. The ancillary metabolic activities of antihypertensive drugs now available differ widely. Diuretics and beta blockers, for example, have potentially adverse metabolic effects, whereas agents such as selective alpha 1-adrenoceptor inhibitors appear to beneficially affect several metabolic cofactors influencing the CAD risk profile. The impact of such drug-induced metabolic changes on overall prognosis of the hypertensive patient remains to be clarified. In the absence of other contraindications, however, it is sensible to use drugs that do not increase the metabolic predilection to precocious CAD.