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Query: UMLS:C0018681 (headache)
 56,091 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. In a cross-over study between hydrallazine and prazosin in fifteen patients, also treated with the beta-receptor-blocking agent propranolol, 1 mg of prazosin was found to be equipotent with 30 mg of hydrallazine. 2. All patients were known to tolerate dydrallazine. In one patient prazosin treatment was discontinued because of severe headache. In four patients minor, non-persistent initial side effects were found. These might have been avoided by using a smaller starting dose. One patient fainted on the second day of prazosin treatment, probably from a micturition syncope. 3. Prazosin may be used as an alternative to hydrallazine. 4. The final status of prazosin as an anti-hypertensive drug is uncertain.20
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PMID:A cross-over study between hydrallazine and prazosin. 79 69

The ability of the alpha-1 adrenoceptor antagonist, prazosin, to reduce the severity and duration of episodes of autonomic dysreflexia was studied in cervical and high thoracic spinal cord injury patients with documented episodes of autonomic dysreflexia. Sixteen patients participated in a double blind parallel group study comparing prazosin 3 mg b.d. with placebo given for 2 weeks. Both groups were matched for age, sex and baseline severity of autonomic dysreflexia episodes. Prazosin was well tolerated and did not produce a significant lowering of resting blood pressure. Compared to baseline measurements, patients allocated to prazosin therapy were found to have fewer severe episodes of autonomic dysreflexia and during these episodes to have significant reductions in average rise in systolic and diastolic blood pressure, symptom duration and requirement for acute antihypertensive medication. The severity of headache during individual autonomic dysreflexia episodes was also diminished with prazosin therapy. No symptom parameter was significantly altered by placebo therapy. It is concluded that prazosin is superior to placebo in the prophylactic management of autonomic dysreflexia and that these findings are consistent with suggestions that alpha-1 adrenoceptors play an important role in the pathogenesis of this syndrome.
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PMID:A study of the alpha-1 adrenoceptor blocker prazosin in the prophylactic management of autonomic dysreflexia in high spinal cord injury patients. 135 86

Isradipine is a dihydropyridine calcium-entry blocking agent with pronounced vasodilator activity and no significant cardiac effects at clinical doses, a desirable profile for an antihypertensive drug. Prazosin, a post-junctional alpha-adrenoceptor blocking agent, may produce a similar hemodynamic pattern. Therefore, we compared the effects of isradipine (2.5-10 mg bid) with those of prazosin (2-8 mg bid) in 83 patients with established essential hypertension, using a randomized, double-blind, parallel-group design. Patients received a placebo for 3-5 weeks, then either isradipine or prazosin over a 6-week titration period, followed by a 4-week plateau phase. During the plateau period, isradipine therapy lowered sitting blood pressure more effectively than did the administration of prazosin: Mean systolic BP fell 16.7 versus 8.1 mmHg (p less than 0.001) and mean diastolic BP was reduced 15.6 versus 12.6 mmHg (p less than 0.01). In the dosing range used (while also noting that prazosin is occasionally titrated up to doses of 30 mg qd), 83% of isradipine-treated patients had at least a 10 mmHg reduction in diastolic BP, compared with 64% of prazosin-treated patients (p = 0.05, FET). Tachyphylaxis did not occur with either drug. The rate of occurrence of side effects was similar in both treatment groups; the most common adverse event seen with isradipine was headache (20%) and with prazosin, dizziness (19%).
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PMID:A multicenter comparison of isradipine and prazosin for treatment of essential hypertension. 214 12

Selective alpha 1 adrenergic receptor blocking agents lower blood pressure by reducing the increased peripheral vascular resistance that characterizes essential hypertension. Prazosin and terazosin have been shown to be well tolerated in clinical practice and seldom cause impotence or metabolic abnormalities. The most common adverse effects--dizziness, headache, and asthenia--are generally well tolerated and infrequently lead to discontinuation of therapy. First-dose syncope can usually be avoided by initiating therapy with low doses administered at bedtime. Finally, the alpha 1 receptor antagonists do not adversely affect such cardiovascular risk factors as hypokalemia, serum lipid profile, and left ventricular hypertrophy. In fact, alpha 1 antagonists reduce total cholesterol and low-density-lipoprotein plus very-low-density-lipoprotein cholesterol and thus may contribute to the overall management of cardiovascular risk by blood pressure reduction and improvement of the serum lipid profile. Since the goal of treating chronic essential hypertension is to improve morbidity and mortality, the choice of therapy should be influenced by the agent's ability to modify as many risk factors as possible. Alpha 1 adrenoreceptor antagonists beneficially impact several cardiovascular risk factors and thus merit consideration as first-line antihypertensive therapy.
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PMID:New perspectives on selective alpha 1 blockade. 257 43

The specific competitive alpha 1-postsynaptic blocking action and haemodynamic effects of prazosin (Minipress) have been summarized. Prazosin causes dilatation of arterioles and veins, reduces total peripheral resistance as well as preload and afterload. Cardiac output does not change at rest, stroke volume and subsequent cardiac output increase during exercise. The changes in heart rate have non-significant. It does not cause sympathetic counter-regulation, plasma renin activity does not increase, aldosterone level decreases, salt- and fluid retention may rarely be observed. It does not provoke angina. The authors report on the results of their examinations with the first dose of prazosin in 61 patients (in 33 cases by the double-blind cross-over method by placebo control), and summarize the observations made with the drug in long-term treatment in Hungary. The authors and other teams used prazosin as a long-term treatment (of approximately 3 months) in combination with other drugs in a total of 344 patients, and as monotherapy in 159 patients. In the course of combination treatment side-effects were observed in 15% of the patients (dizziness, headache, weakness, occasionally palpitation). During monotherapy, side-effects occurred in 12% of the patients (tachycardia, headache, weakness, dizziness). Hungarian results confirm the usefulness of prazosin in all stages of hypertension. It is effective in 30-35% of the cases as a monotherapy (this rate is congruent with the efficacy of beta-blockers, calcium antagonists and antihypertensive drugs of central action). Earlier prazosin had been used as a third agent in combination treatment of hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The mechanism of the action of Minipress. Examinations in hypertension. 257 64

The efficacy and safety of prazosin GITS (gastro-intestinal therapeutic system), a new extended-release once-a-day formulation, were assessed both as monotherapy in mild essential hypertension and in combination with a diuretic in moderate essential hypertension in two multicenter, double-blind, placebo-controlled trials. Prazosin GITS (Minipress XL) given once daily in doses of either 10 or 20 mg significantly reduced sitting and standing systolic and diastolic blood pressure compared with placebo in both mild and moderate essential hypertension. There were minimal, clinically insignificant changes in heart rate following prazosin-GITS treatment (2.5, 10, and 20 mg) compared with placebo treatment. Prazosin GITS was well tolerated; the most common adverse experiences reported were headache, dizziness, and fatigue. All adverse experiences in the moderate hypertension group and the majority (91 percent) in the mild hypertension group were mild-to-moderate in severity. The results from these multicenter trials demonstrate the efficacy and safety of this new extended-release once-a-day formulation of prazosin in the treatment of patients with mild and moderate essential hypertension.
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PMID:Efficacy and safety of Minipress XL, a new once-a-day formulation of prazosin. 266 73

Recent reports have shown that beta-adrenergic blockade may exacerbate variant angina. On theoretical grounds, alpha-adrenergic blockade may be beneficial in these patients. To test this hypothesis, we assessed the efficacy of prazosin, an alpha-adrenergic blocking agent, in six men, mean age 49 years, with variant angina. Prazosin, 14.0 +/- 2.4 mg/day (mean +/- SD) in three equal doses, was compared with placebo in a double-blind, randomized, double-crossover trial lasting 4 1/2 months: 2 weeks of open-label prazosin followed by four 1-month periods of blinded alternating therapy. No other vasoactive medications were administered during the study. Prazosin reduced sitting systolic arterial pressure from 145 +/- 18 to 127 +/- 16 mm Hg (p = 0.02), but exerted no effect on diastolic arterial pressure or heart rate. Prazosin did not change the weekly number of episodes of chest pain (2.5 +/- 2.3 with placebo vs 3.1 +/- 3.0 with prazosin, NS), nitroglycerin tablets used (3.9 +/- 3.7 with placebo vs 4.6 +/- 4.2 with prazosin, NS), or transient ST-segment deviations (by calibrated two-channel Holter monitoring for 24 hours/week throughout the study) (6.5 +/- 10.1 with placebo vs 11.8 +/- 17.4 with prazosin, NS). During prazosin therapy, three patients had orthostatic dizziness and one patient had headache. Thus, in a long-term, randomized, double-blind trial, prazosin exerted no obvious beneficial effect in patients with variant angina.
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PMID:Alpha-adrenergic blockade for variant angina: a long-term, double-blind, randomized trial. 613 37

Earlier nonselective alpha 1-adrenergic blocking drugs such as phentolamine and phenoxybenzamine are now restricted to the pharmacological management of alpha 1-adrenergic crisis and phaeochromocytoma. Prazosin, the first selective alpha 1-blocker approved for the treatment of hypertension, became available in the mid-1970s. Additional alpha 1-blockers such as doxazosin and terazosin have been introduced during recent years. The undesirable effects of all members of this class are similar. Most adverse events can be attributed to reversible competitive antagonism of postsynaptic alpha 1-adrenergic receptors in tissues that sustain high levels of alpha-adrenergic sympathetic tone, e.g. resistance arteries, capacitance veins and the urinary bladder outflow tract. Orthostatic hypotension with a sensation of intense faintness and occasional syncope, can occur shortly after the initial dose. Aggravating factors include upright posture, intravascular volume depletion and concurrent administration of other medications that lower blood pressure, including all other classes of antihypertensive drugs. The problem is reduced or avoided by the choice of low starting doses, beginning treatment at bedtime and by minimising other risks. Among overall adverse effects, asthenia, dizziness, faintness and syncope predominate and occur in 10 to 20% of patients, leading to discontinuation of therapy in about half that number. Infrequent adverse events include headache, drowsiness, palpitations, urinary incontinence and priapism. Some patients experience a 1 to 2kg bodyweight gain which may be associated with secondary hyperaldosteronism. Tolerance appears to develop to the benefits of alpha 1-blockade in patients with congestive heart failure, but not in hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Adverse effects of alpha 1-adrenergic blocking drugs. 791 78

Hypertensive emergencies in hemodialysis require immediate therapy, usually by parenteral drug administration; however, sublingual medications may have potential in this special condition. Sublingual captopril (25 mg), nifedipine (10 mg) and prazosin (2 mg) were prescribed to determine the effectiveness and safety of each medication in the treatment of hypertensive emergencies during hemodialysis. Blood pressure and heart rate were measured continuously up to 120 min postdose. The response rates were 83% for captopril, 90% for nifedipine and 11% for prazosin. The significant hypotensive effects of both sublingual captopril and nifedipine occurred at 10 min and continued up to 120 min. The reduction of systolic blood pressure occurred earlier in nifedipine than captopril (10 vs. 15 min). No significant difference in heart rate between them was noted. There were no side effects in the captopril group but flushing, tachycardia and headache were observed in 4 patients of the nifedipine group. We concluded that sublingual captopril and nifedipine were effective but captopril seemed to have less side effects than nifedipine and may be an excellent alternative to sublingual nifedipine in the urgent treatment of hypertensive emergencies in hemodialysis. Prazosin was not recommended because of its low response rate.
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PMID:Comparison of sublingual captopril, nifedipine and prazosin in hypertensive emergencies during hemodialysis. 824 94