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

The kind of interaction of two structurally different calcium channel blockers (verapamil and nicardipine) with both alpha 2-adrenergic agonist and antagonist binding on human platelets was investigated. Only verapamil, but not nicardipine, interacted in vitro with platelet alpha 2-adrenoceptors on [3H]-yohimbine or [3H]-UK 14,304 binding. Verapamil behaves as a weak antagonist competitor for alpha 2-adrenoceptors. In patients with mild essential arterial hypertension, the number of platelet alpha 2-adrenoceptors as well as velocity of aggregatory response to adrenaline, are significantly decreased: -21 and -25%, respectively (p less than 0.05). Verapamil (120 mg t.i.d. orally during 1 month) failed to modify the platelet alpha 2-adrenoceptor number or the adrenaline-induced platelet aggregation in hypertensive patients. These results show that, although interacting in vitro, verapamil does not modify the alpha 2-adrenergic receptivity after 1 month treatment in humans.
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PMID:Verapamil interacts in vitro with alpha 2-adrenoceptors but does not modify alpha 2-receptivity in vivo. 257 96

Seven healthy male volunteers were studied at the end of 7 days placebo period and after 7 days treatment with verapamil (120 mg twice daily). Verapamil increased significantly plasma renin activity and urinary excretion of 6-keto prostaglandin F1 alpha without significant modification of plasma aldosterone. Metoclopramide (10 mg i. v.) induced a significant increase of plasma aldosterone with the peak values 15 min after the injection of the drug. The results indicate that verapamil does not lead to secondary hyperaldosteronism which is characteristic of most other vasodilators. The increase of prostacyclin, measured as 6-keto prostaglandin F1 alpha can contribute to the efficacy of verapamil in patients with ischemic heart disease and hypertension. The present study suggests that the aldosterone response to metoclopramide is not directly dependent on calcium, but an indirect effect of calcium through renin-angiotensin system cannot be excluded.
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PMID:Effect of verapamil on renin-angiotensin-aldosterone system, urinary 6-keto prostaglandin F1 alpha and aldosterone response to metoclopramide in normal man. 263 2

The effects of one month's treatment with each of nifedipine, verapamil, diltiazem, propranolol and placebo, given in random order, on fasting plasma glucose, haemoglobin Alc, serum fructosamine, immunoreactive insulin, cholesterol, and triglyceride were studied in a group of 19 patients with hypertension and non-insulin dependent diabetes mellitus. The metabolic effects of the active drugs were generally small but fasting plasma glucose was increased by propranolol from 9.3 +/- 3.0 to 10.4 +/- 3.4 mmol/l (P less than 0.01) (mean +/- SD) and to 10.1 +/- 3.2 mmol/l (P less than 0.05) by nifedipine. Serum fructosamine was increased from 2.75 +/- 0.53 to 2.89 +/- 0.62 mmol/l (P less than 0.05) by diltiazem and to 2.91 +/- 0.65 (P less than 0.05) by propranolol. Verapamil increased fasting serum immunoreactive insulin: diltiazem and propranolol tended to reduce it. Propranolol but not the other drugs significantly increased serum triglyceride. Calcium antagonists may be preferable to beta adrenoceptor blockers for the treatment of hypertensive diabetics. Of the three calcium antagonists we studied, verapamil may have advantages over nifedipine and diltiazem.
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PMID:The effects of verapamil, diltiazem, nifedipine and propranolol on metabolic control in hypertensives with non-insulin dependent diabetes mellitus. 265 57

The action of some of the most frequently used antihypertensive drugs (reserpine, clonidine, furosemide, propranolol, verapamil) on carbohydrate metabolism in diabetics was studied in an acute experiment with the help of artificial endocrine pancreas (Biostator). The aim of the study is to facilitate the selection of the most suitable drug to be used in the combination of diabetes and hypertension. 42 patients with diabetes mellitus type II were studied divided into 5 groups of 7 patients each according to the number of drugs examined and a control group also of 7 patients. The drugs propranolol and furosemide exert an unfavourable action both on the beta-cell function and the peripheral insulin efficiency. Verapamil and clonidine influence mainly the insulin secretion by a minimum effect on insulin efficiency. Only the drug reserpine practically does not influence the insulin secretion and efficiency.
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PMID:[Effect of antihypertensive drugs on insulin secretion and efficacy]. 266 37

Although verapamil is a well-established treatment for angina, cardiac arrhythmias and cardiomyopathies, this review reflects current interest in calcium antagonists as anti-hypertensive agents by focusing on the role of verapamil in hypertension. Verapamil is a phenylalkylamine derivative which antagonises calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes. By reducing intracellular free calcium concentrations, verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes. Verapamil is well suited for the management of essential hypertension since it produces generalised systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure. Evidence from clinical studies supports the role of oral verapamil as an effective and well-tolerated first-line treatment for the management of patients with mild to moderate essential hypertension. Clinical studies have shown that verapamil is more effective the higher the pretreatment blood pressure and some authors have found a more pronounced antihypertensive effect in older patients or in patients with low plasma renin activity. Sustained release verapamil formulations are available for oral administration which, as a single daily dose, are as effective in lowering blood pressure over 24 hours as equivalent doses of conventional verapamil formulations given 3 times daily. As a first-line antihypertensive agent, oral verapamil is equivalent to several other calcium antagonists, beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors and other vasodilators, and is not associated with many of the common adverse effects of these treatments. Verapamil may be preferred as an alternative first-line antihypertensive treatment to diuretics in elderly patients because it has similar efficacy in these patients without causing the adverse effects commonly linked with diuretic treatment. Furthermore, because verapamil does not cause bronchoconstriction, it may be used in preference to beta-blockers in patients with asthma or chronic obstructive airway disease. Reflex tachycardia, orthostatic hypotension or development of tolerance is not evident following verapamil administration. As a second- or third-line treatment for patients refractory to established antihypertensive regimens, verapamil produces marked blood pressure reductions when combined with diuretics and/or ACE inhibitors, beta-blockers and vasodilators such as prazosin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Verapamil. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension. 267 May 11

Calcium entry blockers have been used during general anesthesia in order to control hypertension and tachyarrhythmias. It is well known that both calcium entry blockers (CEBs) and inhalation anesthetics have depressant effects on atrioventricular (AV) conduction and sinus automaticity. Therefore, this study was designed to evaluate combined effects of either halothane, enflurane, isoflurane, or sevoflurane and CEBs (verapamil, diltiazem, or nifedipine) on AV conduction. The following 3 sets of experiments were performed using 90 mongrel dogs anesthetized with ketamine 100-150 mg im, thiamylal 25 mg/kg iv and nitrous-oxide with 50% oxygen. Experiment 1: to evaluate the effects of ketamine and thiamylal on AV conduction. Experiment 2: to evaluate drug interactions of halothane with CEBs. Experiment 3: to evaluate the combined effects of four different inhalation anesthetics at equipotent concentrations (0.8% halothane, 1.6% enflurane, 1.2% isoflurane, and 1.7% sevoflurane) and verapamil. The following variables were measured utilizing His bundle electrocardiogram: Sinus cycle length (SCL), AV conduction time (AH interval), His Purkinje conduction time (HV interval), effective and functional refractory period of AV node (ERP and FRP). It was confirmed that ketamine im and thiamylal iv used for induction of anesthesia did not change AV conduction time from experiment 1. The combined effects of either verapamil (0.1 mg/kg) or diltiazem (0.15 mg/kg) and 0.8% halothane were additive on AV conduction. Although nifedipine (0.01 mg/kg) did not affect AV conduction, there was the significant prolongation of SCL with halothane compared to without halothane. In experiment 3, 0.8% halothane and 1.6% enflurane were stronger than 1.2% isoflurane and 1.7% sevoflurane concerning inhibitory effects on AV conduction. Verapamil had some deleterious effects in 1.6% halothane or 3.2% enflurane anesthesia because of extreme inhibitory effects on AV conduction and sinus automaticity. In conclusion, caution must be exercised in usage of CEBs if inhalation anesthetics are used in higher concentrations.
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PMID:[Comparative effects of inhalation anesthetics on atrioventricular conduction with and without calcium entry blockers]. 272 26

Studies of myocardial utilization of fatty acids and analogs has focused on coronary heart disease. This study addresses the topic of radioiodinated fatty acid utilization in hypertensive-cardiomyopathy. The new fatty acid analog 19-iodo-3,3-dimethyl-18 nonadecenoic acid (DMIVN) was studied by autoradiographic microimaging (ARG) in salt-sensitive (S) hypertensive (salt-fed) and in salt-sensitive (S) normotensive (low-salt diet), Dahl-strain rats. A salt fed, S-strain group was treated with verapamil and the results were compared to those in a hypertensive, non-treated group. The distribution of DMIVN in the hearts of normotensive rats was uniform. In the myocardium of hypertensive rats nonuniform DMIVN concentration was seen in the subendocardial and mid-layers of the left ventricle (LV). Verapamil given to salt-fed rats prevented hypertension and uniform DMIVN uptake similar to normotensive controls was seen. The data suggest that DMIVN may be suitable for the detection of hypertension induced myocardial changes and for assessing therapy. The distribution and clearance characteristics of DMIVN indicate that DMIVN may be a useful agent for SPECT imaging in man.
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PMID:Studies of a new fatty acid analog (DMIVN) in hypertensive rats and the effect of verapamil using ARG microimaging. 280 54

Experiments were conducted on five chronically instrumented unanesthetized sheep to determine the effects of verapamil, a calcium channel inhibitor, on the pulmonary hemodynamic and microvascular permeability responses to endotoxemia. Paired control endotoxemia experiments (E) and endotoxemia with verapamil treatment (30-60 micrograms.kg-1.min-1) experiments (V + E) were conducted on each sheep in random order. In the V + E experiments sheep were pretreated with a continuous intravenous infusion of verapamil 1.5-2.0 h before endotoxin infusion (1.0 microgram/kg, given over 15 min). Verapamil significantly increased base-line pulmonary arterial pressure, left atrial pressure, lung lymph flow rate, and circulating blood leukocyte levels and significantly decreased base-line cardiac output. During the endotoxin response, verapamil significantly attenuated both phase I pulmonary arterial hypertension and phase II lung lymph flow rate compared with control endotoxin experiments. The results indicate that verapamil attenuates both the pulmonary hemodynamic and increased lung microvascular permeability response to endotoxin in sheep. In a series of in vitro experiments, verapamil was found to be a potent inhibitor of phorbol myristate acetate-induced superoxide production in isolated sheep granulocytes. These data suggest that the beneficial in vivo effects of verapamil during endotoxemia may in part be due to its inhibition of increased free cytosol calcium concentration and/or inhibition of toxic O2 metabolite production.
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PMID:Verapamil attenuates lung vascular responses to endotoxin in sheep. 285 Feb 94

1. Calcium antagonists, including verapamil, are now used widely in the management of patients with hypertension. 2. Six weeks of chronic therapy with verapamil (50 mg/kg per day, orally) to produce a plasma level of 80-100 ng/ml in Sprague-Dawley rats depletes cardiac noradrenaline (NA) without apparently causing beta 1 adrenoceptor 'up' regulation. 3. The effect of verapamil on cardiac NA is rapidly reversed upon verapamil withdrawal. 4. Chronic therapy with nisoldipine (100 mg/kg per day, orally) had no effect on cardiac NA. 5. Verapamil (50 mg/kg per day, orally) and nisoldipine (100 mg/kg per day, orally) therapy for 6 weeks prevented the time-dependent increase in systolic blood pressure in SHR rats. 6. Binding studies with (-)[3H]-D888 (desmethoxyverapamil) indicated that the affinity of the phenylalkylamine binding sites is higher in hearts of SHR relative to hearts from age-matched (25 weeks) WKY and SD, without any change in density.
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PMID:Calcium antagonists and hypertension. 285 52

The demonstration that antihypertensive drug treatment reduces mortality and morbidity in persons with mild hypertension has extended the indications for treatment. Verapamil, nitrendipine, angiotensin converting enzyme inhibitors and beta-adrenoceptor blocking drugs are equally effective in reducing blood pressure. The choice of which drug to use depends on the presence or absence of specific contraindications and the occurrence of adverse effects in the individual patient.
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PMID:Comparison of calcium antagonists with other antihypertensive agents. 286 75


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