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

Verapamil, a calcium-entry blocker, and sodium nitroprusside, a non-specific vasodilator, were infused into the blood-perfused hindlimbs of New Zealand genetically hypertensive rats (NZGH) and spontaneously hypertensive rats (SHR), two genetic models of hypertension, and their normotensive controls, New Zealand normotensive rats and Wistar-Kyoto rats (WKY). Vasodilator responses, measured as the falls in perfusion pressure from the initial values, were similar and increased in NZGH and SHR. The responses were strongly dependent on the initial level of perfusion pressure in each strain of rat. It is concluded that increased vascular resistance, rather than a qualitative difference in vasodilator mechanisms, accounts for the enhanced responses to verapamil and sodium nitroprusside in NZGH and SHR hindlimbs.
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PMID:Effect of verapamil and sodium nitroprusside on hindlimb vascular resistance in New Zealand genetically hypertensive and Japanese spontaneously hypertensive rats. 324 Dec 80

Calcium channel blocking drugs are a chemically heterogenous group, so it might be expected that their effects on vascular smooth muscle, cardiac contractility, and conduction tissue may differ. However, the majority of adverse reactions are predictable from their pharmacological actions and may be conveniently grouped in the following categories: 1) vasodilatation, 2) negative inotropic effects, 3) conduction disturbances, 4) gastrointestinal effects, 5) metabolic effects, and 6) drug interactions. Vasodilatory symptoms, namely, dizziness, headaches, flushing sensation, and palpitation, are more likely with nifedipine. Peripheral edema is also common with nifedipine, but the mechanism is uncertain. For a given degree of vasodilation, the greatest negative inotropic effect is seen with verapamil first, diltiazem second, and nifedipine last. Calcium channel blocking drugs are contraindicated in hypertensive patients with second and third degree heart block, sick sinus syndrome, and severe heart failure. Verapamil and diltiazem have a significant effect on cardiac conduction, whereas nifedipine, in therapeutic doses, does not. Local gastrointestinal symptoms, such as nausea and constipation, are common with verapamil. None of the calcium channel blocking drugs have been reported to adversely affect lipid or protein metabolism. However, nifedipine, verapamil, and diltiazem in high doses may inhibit liberation of insulin. The significance of this finding needs to be explored further in hypertensive diabetics. Serum digoxin levels have been shown to increase after administration of verapamil and nifedipine, but there is no evidence that this change has any clinical relevance.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1988 Mar
PMID:Side effects of calcium channel blockers. 328 Apr 92

The availability of calcium antagonists has provided yet another therapeutic option in the management of hypertension. Calcium antagonists lower the blood pressure in hypertensive individuals while preserving the blood flow at the microcirculatory level. While all the available calcium antagonists are effective in the treatment of hypertension, they differ in their hemodynamic and pharmacologic actions. Nifedipine appears to be suitable for immediate treatment of severe hypertension and for chronic treatment of uncomplicated or refractory hypertension. In some but not all patients, co-administration of a beta-blocker is necessary to blunt reflex tachycardia. This problem is less likely with the tablet/long-acting formulation of nifedipine. Verapamil and diltiazem are useful as initial therapy for chronic mild-to-moderate hypertension. They are as effective as other first-line drugs in the treatment of uncomplicated hypertension. The heart rate with verapamil or diltiazem does not change or is slightly reduced, thus contrasting with nifedipine. Experience to date suggests that calcium antagonists do not cause adverse biochemical effects and in this respect are superior to diuretics and certain beta-blockers. Currently, verapamil is available as a sustained release preparation. In the near future, nifedipine or diltiazem may also be available in the long acting formulation to permit simplicity and to enhance patient compliance in the treatment of hypertension.
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PMID:Calcium antagonists in the treatment of hypertension. An overview. 328 42

The antihypertensive effect and possible adverse effects of verapamil were assessed in 30 Thai patients with mild to moderate hypertension. All patients had normal blood chemistry evaluations and electrocardiograms. After a 4-week placebo period, 80 mg of verapamil was given 2 times a day for 8 weeks. Blood pressure and pulse rate were recorded both in supine and standing positions every 2 weeks. Verapamil decreased blood pressure significantly both in supine and standing positions. The pulse rate was not significantly affected. The most common adverse effect was constipation. No vivid dreams or breathlessness were reported. The blood chemistry and electrocardiograms at the end of the study period were not significantly changed. It is concluded that verapamil reduces blood pressure in mild to moderate hypertensive Thai patients.
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PMID:A multicenter study of verapamil in systemic hypertension in Thailand. 351 11

Many studies have confirmed that the treatment of mild and moderate hypertension reduces mortality and morbidity from cardiovascular accidents and cardiac and renal failure; more recent studies suggest that there is some beneficial effect on ischemic heart disease. The harmful metabolic effects of some hypotensive agents on serum potassium, magnesium, uric acid, glucose, renin and lipids might reduce the beneficial effect of controlling raised blood pressure. Also, the adverse effects associated with most antihypertensive drugs have decreased quality of life and, possibly, compliance in many patients. In assessing the value of newer antihypertensive agents, other effects of the drugs must be taken into account. The calcium-channel antagonist verapamil produces a dose-dependent reduction in blood pressure with little postural effect. There is little change in heart rate and the major antihypertensive effect results from a decrease in peripheral vascular resistance, with no accompanying increase in cardiac output. In 75 patients followed for more than 1 year, tolerance to verapamil did not appear to develop, nor were there any significant changes in serum electrolytes or creatinine clearance. Fasting serum lipid levels were measured in 15 patients before and after 3 months of treatment with verapamil (80 to 160 mg, 3 times a day); there was no change in cholesterol, triglycerides or high-density lipoproteins. Verapamil is, therefore, an effective hypotensive agent with a rapid onset of action. Tolerance does not develop with prolonged use, nor does it appear to affect electrolytes or serum lipids adversely. Constipation appears to be its only limiting adverse effect.
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PMID:Long-term results with verapamil in essential hypertension and its influence on serum lipids. 351 14

Recent reports have confirmed that some slow calcium channel inhibitors have useful antihypertensive properties because they produce dilatation of the peripheral arterioles without reflex tachycardia. Verapamil is such a drug, but its clinical role in the management of hypertension is not clear. An open crossover trial was performed to compare the 24-hour profiles of blood pressure reduction after long-term therapy with a standard beta-adrenoceptor blocker, propranolol, and verapamil. Nineteen patients were studied by continuous ambulatory intraarterial recording and the order of drug administration was determined by random allocation. The drugs were administered 2 times a day and titrated according to casual clinic pressures (propranolol, 40 to 240 mg 2 times a day; verapamil, 120 to 240 mg 2 times a day). Mean hourly blood pressure and heart rate values were obtained over a 24-hour cycle and the responses to isometric and dynamic exercise were also examined. The drugs produced a uniform and comparable reduction in blood pressure throughout the day, together with a reduction in heart rate, which was greater with propranolol. Comparable effects were also seen on the pressor responses to exercise. Both drugs were equally well tolerated and caused no patient withdrawals. Thus, oral verapamil given 2 times a day shows a degree of efficacy similar to that of propranolol and provides 24-hour blood pressure control. This slow calcium channel inhibitor was well tolerated and may be used as initial therapy for hypertension.
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PMID:Twice-daily verapamil for hypertension: a comparison with propranolol. 351 19

We compared verapamil and propranolol hydrochloride for monotherapy of hypertension. Verapamil lowered blood pressure (BP) more effectively than propranolol in black and white patients. Verapamil was equally effective in blacks and whites, whereas propranolol was more effective in whites. Heart rate was reduced by 6.0 beats per minute by verapamil, and by 13.6 beats per minute by propranolol. In blacks, verapamil lowered systolic BP 16.9 vs 8.1 mm Hg for propranolol; verapamil reduced diastolic BP 12.8 vs 8.6 mm Hg for propranolol. In whites, verapamil lowered systolic BP 19.0 vs 12.7 mm Hg for propranolol; verapamil reduced diastolic BP 16.7 vs 12.3 mm Hg for propranolol. Increases in systolic BP were observed in 22% and 3.4% of patients receiving propranolol and verapamil, respectively. The PR interval was increased from 163.5 to 174.9 ms for verapamil vs 160.3 to 164.4 ms for propranolol. Constipation (15%) and headaches (10%) were most frequent complaints for verapamil vs fatigue (18%) and dizziness (7%) for propranolol. Changes in blood biochemistry values were of small magnitude. We conclude that verapamil monotherapy is a safe and effective means of achieving BP control in patients with essential hypertension.
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PMID:A comparison of verapamil and propranolol for the initial treatment of hypertension. Racial differences in response. 353 60

The calcium antagonists diltiazem, nifedipine and verapamil are widely used in the treatment of coronary heart disease, arterial hypertension, certain supraventricular tachyarrhythmias and obstructive hypertrophic cardiomyopathy. During recent years their pharmacokinetic properties and metabolism have been studied in more detail. Although these 3 calcium antagonists exhibit great diversity in chemical structure, they exhibit common pharmacokinetic properties. These drugs are extensively metabolised and only traces of unchanged drugs are eliminated in urine. Their systemic plasma clearances are high and dependent on liver blood flow. Therefore, their bioavailabilities (diltiazem 40 to 50%; nifedipine 40 to 50%; verapamil 10 to 30%) are low despite almost complete absorption following oral administration. During long term treatment, oral clearance decreases and bioavailability increases due to saturation of hepatic first-pass metabolism. Pronounced intra- and inter-individual variations in clearance and bioavailability are observed. In patients with liver cirrhosis the various pharmacokinetic parameters are grossly altered. Clearance decreases, elimination half-life is substantially prolonged, and bioavailability more than doubles. In addition, the volume of distribution increases. Whereas renal disease has no impact on the pharmacokinetics of diltiazem and verapamil, elimination half-life of nifedipine increases in relation to the degree of renal impairment due to an increase in volume of distribution. Systemic clearance, however, remains unchanged. The data so far available indicate that the plasma concentrations of these drugs correlate with both their electrophysiological and haemodynamic effects. However, no effective therapeutic plasma concentration range has been firmly established. As reliable clinical end-points are available for dose titration of calcium antagonists, it is doubtful whether therapeutic drug monitoring will be of great value. Calcium antagonists are often administered in combination with a variety of other drugs. Thus, the potential for both pharmacodynamic and pharmacokinetic drug interaction exists. The interaction between digoxin and these drugs is of clinical importance. Verapamil and diltiazem cause a significant increase in plasma digoxin concentrations. In contrast, nifedipine does not lead to a significant increase in the plasma digoxin concentration. The mechanism responsible for this interaction is inhibition of both renal and non-renal digoxin clearance.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Clinical pharmacokinetics of verapamil, nifedipine and diltiazem. 354 36

In a single-blind, placebo-controlled crossover study the effects of verapamil (450 +/- 30 mg/day) and propranolol (160 +/- 20 mg/day) on endurance time during submaximal exercise were compared in eight patients with essential hypertension. The drugs were given in randomized order. Each active drug period was preceded by a placebo phase. Endurance tests were performed during both placebo periods and treatment with verapamil and propranolol by bicycle ergometry. Both drugs were equally effective in decreasing resting blood pressure. Verapamil and propranolol reduced exercise heart rate, the effect of propranolol being more pronounced. With placebo, endurance time during exercise was 57 +/- 11 minutes; with propranolol it was 32 +/- 7 minutes (P less than 0.05). Verapamil had no influence on endurance time. The study demonstrates that in contrast to propranolol, verapamil has no influence on exercise tolerance during submaximal work in patients with hypertension.
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PMID:The effects of verapamil and propranolol on exercise tolerance in hypertensive patients. 355 58

Hypersensitivity reactions to heparin preparations with a wide spectrum of clinical manifestations have been reported frequently in the past, but are a rarity now. A 88 year old man was admitted for physical therapy of a collum femoris fracture. Treatment with a diuretic, Reserpine and Verapamil was continued. Chest x-ray revealed a large thoracic aortic aneurysm. From the 12th to the 18th day of low dose heparin prophylaxis with calcium heparin, 7500 U twice daily, at least eight attacks of asthma or cyanosis were observed, starting about two hours after heparin injection. The last attack began suddenly with wheezing, tachypnoea and cough and was associated with apprehension, a sudden blood pressure increase and severe cyanosis. Ventilation improved with oxygen and a beta 2-stimulator, but hypertension and cyanosis lasted for three hours. After discontinuation of heparin no further attacks occurred. Causes other then heparin could not be found. Despite the use of porcine mucosa heparin, avoidance of preservatives and use of low doses a hypersensitivity reaction occurred in our case. The delayed onset after preceding subcutaneous application as well as difficulties in separating the reaction from complications of underlying disease may delay heparin discontinuation.
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PMID:[Asthma attacks in low-dose preventive use of heparin in a male with femoral neck fracture and aortic aneurysm]. 366 60


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