Articles: adrenergic-alpha-antagonists-therapeutic-use.
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The various antihypertensive agents reduce blood pressure by different mechanisms. Alpha-1 receptor blockers reduce vascular resistance and maintain cardiac output. Chronic treatment with beta blockers without intrinsic sympathomimetic activity produces a fall in blood pressure which is associated with a fall in cardiac index and heart rate. ⋯ They should not be used in patients with bronchial asthma, reduced peripheral blood flow, or heart failure. Labetalol reduces blood pressure in a somewhat larger fraction of patients than the pure alpha- or beta-blocking agents. It is hoped that its long-term results will include regression of cardiovascular damage, improved quality of life, and increased life expectancy.
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Randomized Controlled Trial Comparative Study Clinical Trial
Efficacy of terazosin as an antihypertensive agent.
A total of 713 patients with hypertension were evaluated in eight randomized, double-blind, placebo-controlled trials of terazosin administered in single daily doses ranging from 1 to 40 mg. In three of these studies, terazosin or placebo was added to ongoing antihypertensive drug therapy. Patient response was categorized (from excellent to inadequate) according to the change in supine diastolic blood pressure from baseline and the value at the final visit. ⋯ Overall, 52 percent of terazosin-treated patients in these eight studies, compared with 30 percent of placebo-treated patients, had good to excellent responses. Subgroup analysis revealed that blood pressure response was not dependent on sex or age, although white patients appeared to achieve better responses to terazosin in comparison with placebo than did black patients. These studies demonstrate that terazosin administered once daily, either as monotherapy or in combination with other antihypertensive agents, effectively controls blood pressure in patients with mild to moderate hypertension.
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Int J Clin Pharmacol Ther Toxicol · Nov 1985
ReviewCurrent status of labetalol, the first alpha- and beta-blocking agent.
Labetalol is a unique antihypertensive agent which is a competitive peripheral antagonist at both alpha- and beta-adrenoceptor sites. Clinically, it possesses about one fourth of the beta-adrenoceptor blocking activity of propranolol and one half of the alpha-adrenoceptor blocking activity of phentolamine with a beta- to alpha-blocking ratio of approximately 7:1. Nowadays, the clinical profile of labetalol is clearly defined. ⋯ In induced hypotension during anesthesia and surgery no invasive blood pressure measurements are needed. The most frequent adverse effects include fatigue, postural hypotension, headache and gastrointestinal complaints. On the whole, labetalol expands the armamentarium of the practising physician in the treatment of hypertension of different origin.
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We tested our clinical impression that black hypertensives in our clinic population responded better to alpha-adrenergic blocking agents (clonidine and prazosin) than to beta-adrenergic blockers (atenolol, nadolol and propranolol). Compared to no effect from eight weeks of therapy with beta-blockers, clonidine significantly decreased erect mean arterial pressure (MAP) when assessed weekly for four weeks (p = 0.027 to 0.046). However, the decrease in supine MAP was not significant. ⋯ Supine MAP was significantly less than with beta-blockade (p = 0.032) at two weeks but not at four weeks and decrements in erect MAP were not significant. In this preliminary study, black hypertensives appeared to be more responsive to alpha-adrenergic antagonists than to beta-blockers, with clonidine more effective than prazosin. Elucidation of possible mechanisms of the difference and of its clinical importance warrant further study.