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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The effects of prazosin administered alone or in combination were studied in thirty patients between August 1974 and March 1975. 2. All patients had previously received treatment for hypertension with other agents, for from 2 months to 10 years. All thirty patients had refractory hypertension which had not responded satisfactorily to other treatment. 3. Patients were treated initially with prazosin; polythiazide, or polythiazide plus tolamolol, were added when necessary. 4. A satisfactory blood pressure response to prazosin alone, or prazosin in dual or triple combination therapy, occurred in all thirty patients. 5. Prazosin was well tolerated.
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PMID:A study of the use of prazosin in hypertensive patients in Korea. 107 91

Prazosin was used as an additional antihypertensive agent for treating 16 patients with hypertension and significant renal functional impairment. The drug was effective in 13 patients at a mean daily dose of 7.9 mg. The most important side effect of prazosin treatment was dizziness which occurred on standing or following exertion, and was seen either after the first dose or following a large increase in dose. This could be prevented by giving the very first dose of 0.5 mg late in the evening. Five patients complained of palpitations. In no patient was there a deterioration in renal function which could be attributed to prazosin. Five women had a significant improvement in renal function.
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PMID:Prazosin in the treatment of patients with hypertension and renal functional impairment. 107 80

There is evidence that cardiac hypertrophy in spontaneously hypertensive rats (SHR) occurs before the development of hypertension. 1,2-Diacylglycerol, which is thought to be a second messenger activating protein kinase C, is also produced in excess in SHR hearts at 4 weeks of age, before established hypertension. We determined myocardial 1,2-diacylglycerol content in SHR with and without prazosin and enalapril from 3 to 4 weeks of age. Hearts from untreated SHR had greater RNA and DNA synthesis and greater relative weights at 4 weeks of age than those from Wistar-Kyoto (WKY) rats. There was no difference in triglyceride content or phospholipid species between WKY rats and untreated SHR, except for a higher cholesterol content in SHR. Treatment of SHR with enalapril, but not prazosin, lowered not only 1,2-diacylglycerol content but also RNA synthesis to the levels of WKY rats. Moreover, fatty acids involved in 1,2-diacylglycerol were altered by enalapril despite the lack of a difference between WKY rats and untreated SHR. Prazosin did not have any effect on 1,2-diacylglycerol fatty acid composition. Enalapril may decrease cardiac hypertrophy in SHR by lowering myocardial 1,2-diacylglycerol production.
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PMID:Enalapril reduces the enhanced 1,2-diacylglycerol content and RNA synthesis in spontaneously hypertensive rat hearts before established hypertension. 138 Oct 46

Respiratory and cardiovascular effects of midaglizole (DG-5128, CAS 66529-17-7) were investigated in comparison with yohimbine, idazoxan and tolbutamide. 1. Respiration: Midaglizole had little or no effect on respiration of anesthetized dogs. Yohimbine and idazoxan augmented respiration at low dose. Tolbutamide depressed respiratory rate and depth at high dose. 2. Blood pressure and heart rate: Midaglizole produced dose-related hypotension and bradycardia in anesthetized dogs which had laparotomy, whereas it had little or no effect on blood pressure and heart rate of dogs which had no laparotomy (unlaparotomized dogs). Tendency of slight hypertension was observed after high dose of tolbutamide in laparotomized dogs, and transient hypotension was induced in unlaparotomized dogs. Yohimbine and idazoxan increased blood pressure at low dose in unlaparotomized dogs. In laparotomized dogs, yohimbine produced hypertension and hypotension at low and high doses, respectively. In isolated guinea pig atria, midaglizole produced bradycardia which was not observed after yohimbine. Tolbutamide decreased the pulse rate at high concentration. 3. Cardiac contractility: Midaglizole produced increase in cardiac contractility of anesthetized dogs. Yohimbine and idazoxan, at low dose, showed similar inotropic activity. Prazosin also produced a positive inotropic effect, whereas tolbutamide lacked the activity. The inotropic effects of midaglizole and yohimbine were antagonized by pretreatment with propranolol or hexamethonium, whereas a similar effect of prazosin was not influenced by both blockers. In isolated guinea pig atria, midaglizole showed slight inotropic activity. Yohimbine was without any effect, whereas tolbutamide reduced the contractile force. 4. Femoral blood flow: Midaglizole produced a transient increase in femoral blood flow and a decrease in femoral arterial resistance of anesthetized dogs. Yohimbine and idazoxan, at low dose, showed similar vasodilator activity. Prazosin also produced a vasodilator effect, whereas tolbutamide lacked the activity. The vasodilator effects of midaglizole and yohimbine were not affected with propranolol, but inhibited after hexamethonium. 5. Mesenteric blood flow: Midaglizole significantly decreased mesenteric blood flow and increased the arterial resistance of anesthetized dogs in a dose dependent manner. Tolbutamide induced a decrease in blood flow and an increase in arterial resistance only at the highest dose used. Yohimbine increased mesenteric blood flow at low dose and decreased it at high dose. 6. Renal blood flow: Midaglizole dose-relatedly decreased renal blood flow of anesthetized dogs. Tolbutamide and yohimbine at high dose produced a long-lasting decrease of the blood flow. Midaglizole produced a slight transient reduction of renal arterial resistance which was followed by a slight increase. Tolbutamide increased the arterial resistance at high dose.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Pharmacological studies with the alpha 2-adrenoceptor antagonist midaglizole. Part I: Respiratory and cardiovascular systems. 167 73

1. We compared the alpha 1-, alpha 2- and beta 1-adrenoceptor blocking potencies of labetalol with those of its two stereoisomers (RR and SR) in pithed rats and in homogenized rat cerebral cortex and heart. 2. In pithed rats, labetalol and the RR-SR combination were given orally either at doses of 25 and 50 mg kg-1 body wt. or intravenously at doses of 1 and 5 mg kg-1 body wt. Prazosin 4 and 20 micrograms kg-1 body wt. and propranolol 1 and 5 mg kg-1 body wt., were given intravenously for comparison studies of potency at alpha 1- and beta 1-adrenoceptors, respectively. Effects were studied before and after i.v. administration of either phenylephrine (at doses which increased the mean arterial pressure by approximately 80 mmHg) or isoprenaline (at doses that increased heart rate by approximately 100 beats min-1). 3. In pithed rats, labetalol and the RR-SR combination antagonized, in a dose-dependent manner, the pressor effect of phenylephrine (P less than 0.05) and the chronotropic effect of isoprenaline (P less than 0.05). Following both oral and intravenous dosing, the RR-SR combination was twice potent as labetalol in terms of alpha 1- and beta 1-adrenoceptor antagonism at equivalent doses. 4. Labetalol and the enantiomers lacked affinity at alpha 2-adrenoceptors while at alpha 1-adrenoceptors the order of potency was prazosin much greater than RR-SR greater than labetalol. At beta 1-adrenoceptors, the affinity of the compound RR-SR was about 3 times that of labetalol.5. As labetalol is a mixture of active (RR and SR) and inactive (SS and SR) enantiomers (in terms of alpha and beta receptor actions), the combination of RR and SR may be a valuable substitute for labetalol in the treatment of systemic hypertension. Although the potential for non-specific side effects (common to all four enantiomers) could be expected to be diminished, recent reports by postmarketing surveillance indicate that the RR isomer (dilevalol) can induce liver toxicity. Interestingly, labetalol is devoid of this effect; whether the combination of RR and SR enantiomers could be of clinical importance warrants further investigation.
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PMID:The alpha- and beta-adrenoceptor blocking activities of labetalol and its RR-SR (50:50) stereoisomers. 168 67

The cardiovascular responses of 24 healthy young adult males with a parental history of hypertension and 24 males without a parental history of hypertension to an extended active-coping psychological stressor were compared under three drug conditions: placebo, the beta 1-blocking agent metoprolol, and the alpha 1-blocking agent prazosin. In the placebo condition, offspring of hypertensives exhibited significantly greater heart rate, blood volume pulse, and forearm blood flow responses to the task. They also exhibited a significantly greater initial decrease in forearm vascular resistance, which, in contrast to the offspring of normotensives, was no longer significantly different from baseline levels by the end of the session. No group differences in blood pressure response were observed. Metoprolol eliminated the differences in heart rate and forearm vascular resistance responses. Prazosin eliminated the difference in blood volume pulse response and elicited a sustained group difference in forearm vascular resistance. These results implicate the sympathetic nervous system in the exaggerated cardiovascular responsivity to psychological stress in individuals with a family history of essential hypertension. They also suggest that the pattern of increasing vascular resistance in response to this stressor observed in this and other studies in this laboratory reflects alpha-adrenergic activity and not neurohumorally independent autoregulation.
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PMID:Exaggerated sympathetic nervous system response to extended psychological stress in offspring of hypertensives. 188 58

Increased vascular peripheral resistances is the most frequent hemodynamic modification found in arterial hypertension. Arterial vasodilators therefore seem to be an appropriate therapeutic mean in this pathology. Alpha inhibitors to which prazosin belongs are potent arterial vasodilators. Prazosin's new galenic form will allow a larger therapeutic field.
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PMID:[Alpha-1 inhibition. Knowledge and prospectives]. 198 64

The effect of the selective 5-HT2 agonist (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI) on arterial pressure (AP), heart rate (HR), renal blood flow (RBF) and plasma renin activity (PRA) was determined in conscious rats. DOI increased AP and PRA, but decreased HR and RBF. All responses to DOI were abolished by central (LY 53857) or peripheral (xylamidine) 5-HT2 antagonists. Prazosin did not alter the AP or HR response to DOI. Chlorisondamine abolished the bradycardia but slightly increased the hypertension produced by DOI, while enalapril attenuated the pressor response. No further reduction was produced by the combination of enalapril and prazosin. Propranolol attenuated but did not eliminate the renin response, and blocked the bradycardia elicited by DOI. The data suggest that DOI activates 5-HT2 receptors located on vascular smooth muscle and/or the circumventricular organs of the brain to: (1) increase AP and reflexly decrease HR, (2) decrease RBF and (3) increase PRA. The hypertension is mediated by angiotensin II and direct vascular effects whereas the increase in PRA is mediated by an interaction of increased sympathetic nerve activity and decreased renal perfusion pressure.
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PMID:Hemodynamic and renin responses to (+-)-DOI, a selective 5-HT2 receptor agonist, in conscious rats. 218 26

Prazosin (Minipress) monotherapy was given to 152 patients with essential hypertension for one year in a multi-center study involving 13 hospitals and university clinics. In three centers serum levels of total cholesterol, HDL-cholesterol and triglycerides were also determined in 32 patients with hypertension and hyper/dys-lipoproteinemia. As a consequence of Minipress monotherapy significant decreases were found in serum level of cholesterol (after three months and also after one year), triglycerides (after one year), while the serum concentration of HDL-cholesterol increased. Atherogenic index (a ratio of total cholesterol over HDL-cholesterol) was significantly decreased by Minipress. As new data showing a causative correlation between hypertension and hyperlipoproteinemia were published in the literature authors, on the basis of their results, suggest to determine lipid profile in every patient with hypertension. They regard Minipress as the first line drug in young patients with "familial dyslipidemic hypertension". When choosing an antihypertensive drug metabolic side effects should be taken into consideration.
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PMID:[The anti-lipidemic effect of Minipress]. 236 61

Prazosin and terazosin are two alpha 1-adrenoceptor blocking agents, their principal difference being the longer half-life of terazosin. The present study was carried out to determine if elderly subjects are different from the young in their pharmacokinetic handling of these two drugs and if age influences the blood pressure response to each drug. Ten young healthy subjects (aged 19-30 years) and five older healthy subjects (aged 54-62 years) received 1 or 2 mg terazosin, 1 or 2 mg prazosin, or placebo 1 week apart according to a 5 X 5 Latin square design. Concentrations of prazosin and terazosin were measured using a high-performance liquid chromatographic procedure with a detection limit of approximately 0.25 ng/ml. Pharmacokinetic parameters of prazosin were virtually the same in both groups, whereas mean terazosin plasma concentrations were higher in the older group and pharmacokinetic analysis revealed higher peak plasma concentrations and a longer terminal elimination half-life. There was no evidence of increased sensitivity to the hypotensive action of the drug, as peak upright blood pressure falls were similar in the two groups. Symptoms of dizziness in the upright position were also less common. In view of their lack of sedative effects and minimal metabolic disturbances, further studies should be conducted to assess the suitability of these drugs as monotherapy for hypertension in elderly patients.
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PMID:Effect of age on pharmacokinetics of and blood pressure responses to prazosin and terazosin. 244 Nov 67


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