Clinical experience with doxazosin in general medical practice

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.

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.

Clinical experience with doxazosin in general medical practice in The Netherlands

This study was designed to investigate the efficacy and toleration of once-daily doxazosin in the treatment of essential hypertension (sitting diastolic blood pressure 95 to 115 mm Hg) in a general medical practice. Fifty-three patients with mild or moderate essential hypertension entered a study of 14 weeks' duration. This consisted of a baseline run-in period of 2 weeks, a dose-adjustment phase with doxazosin (8 weeks), and a maintenance phase of 4 weeks. Doxazosin was initiated at 1 mg/day, and every 2 weeks the dose was doubled unless blood pressure was normalized (sitting diastolic blood pressure less than or equal to 90 mm Hg with greater than or equal to 5 mm Hg reduction from baseline) or significant side effects emerged. The maximum daily dose administered was 8 mg. Doxazosin produced a significant (p less than 0.05) final mean change in sitting blood pressure of -17.4/-12.2 mm Hg at a final mean daily dose of 4.1 mg. Heart rate was not significantly altered. A nonsignificant decrease in total cholesterol concentration (-2.66%, p = 0.06) and triglycerides (-8.80%, p = 0.09) was also observed. The effect of doxazosin on blood pressure and serum cholesterol resulted in a significant (p less than 0.001) reduction of 19% in calculated risk of coronary heart disease. The investigators' assessment of patient toleration of doxazosin was excellent or good in 86.8% of patients.

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.

An open, noncomparative study of doxazosin in essential hypertension: experience in general practice in The Netherlands

The antihypertensive efficacy, safety, and lipid effects of doxazosin, a selective alpha 1-inhibitor, were assessed in a general practice setting. Three hundred twenty-six patients were entered into the study, which involved three phases: (1) a 2-week baseline period, (2) an 8-week period in which patients received 1 to 8 mg of doxazosin once daily, and (3) a 4-week maintenance period. After 12 weeks, 78.8% of efficacy-evaluable patients were considered therapy successes (sitting diastolic blood pressure either less than or equal to 90 mm Hg with greater than or equal to 5 mm Hg reduction from baseline or greater than or equal to 10 mm Hg reduction from baseline). The mean daily dose in patients considered a therapy success was 2.8 mg. By the final visit, sitting systolic/diastolic blood pressures of these patients were reduced by 16.4/13.5 mm Hg from a mean baseline of 170/106 mm Hg. The investigators' global assessment of efficacy of once-daily doxazosin therapy was excellent or good for 70% of patients. Of the 326 patients, 30.7% reported a total of 160 side effects; 78% of the side effects were mild or moderate in severity, and 24 patients (7.4%) discontinued treatment because of adverse experiences. The investigators' global assessment of toleration was excellent or good for 87% of patients. Doxazosin produced a significant decrease in total cholesterol (p = 0.02) and triglyceride (p less than 0.001) levels. From baseline to final visit there was also a highly significant reduction of 17% (p less than 0.001) in calculated risk score for coronary heart disease on the basis of the Framingham Heart Study risk equation.

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.

Pharmacotherapeutic stature of doxazosin and its role in coronary risk reduction

In hypertension the primary pathophysiologic abnormality is a generalized increase in the peripheral vascular resistance as a result of concentric narrowing of the systemic arterioles, as a result of alpha 1-receptor stimulation. Such stimulation is attenuated by the selective alpha 1-inhibitor doxazosin. The pharmacologic attributes of doxazosin are translated into direct relaxation of the peripheral arteriolar resistance vessels and venous capacitance system, particularly those with a high alpha-adrenoceptor population. The direct effects of such vascular dilatation are immediately beneficial to the heart in reducing systemic and pulmonary vascular pressures that reduce left ventricular wall stress and myocardial oxygen consumption. In clinical studies doxazosin has been found to have a plasma half-life of 19 to 22 hours, of which a single daily dose is sufficient to control hypertension. The antiatherogenic changes in the blood lipid profile resulting from long-term treatment with doxazosin can also be expected to advance its primary prevention potential in hypertensive patients, which is in marked contrast to the potentially disadvantageous changes in the blood lipid profile that follow treatment with beta-blockers and thiazide diuretics. The therapeutic efficacy of doxazosin has been confirmed, irrespective of hypertension severity, age and race of the patient, or the presence of renal impairment or diabetes mellitus. Its side-effect profile is not substantially different from that of placebo or other antihypertensive drug treatment. Given its unique actions regarding antihypertensive efficacy, together with favorable effects on blood lipids, doxazosin probably holds more promise for the prevention of precocious coronary heart disease in hypertensive patients than any other currently available antihypertensive agent.