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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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. Beta blockers with strong intrinsic sympathomimetic activity showed reduced heart rate during exercise. Labetalol reduces cardiac output and peripheral vascular resistance with little or no reduction in peripheral blood flow. Alpha-1 blockers are suitable for patients with active life-styles, with peripheral vascular disorders, or with high blood-cholesterol levels. Beta blockers are useful in patients who have tachycardia, palpitation problems, or angina pectoris, or who have survived a heart attack. 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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PMID:The hemodynamic effects of adrenergic blocking agents. 135 Feb 35

High blood pressure (BP) complicates approximately 10% of all pregnancies. Hypertension in pregnancy falls into four categories: (1) preeclampsia-eclampsia, (2) chronic hypertension of whatever cause, (3) preeclampsia-eclampsia superimposed to chronic hypertension or renal disease, and (4) transient or late hypertension (gestational hypertension). Preeclampsia, the association of hypertension, proteinuria, and edema, accounts for more than 50% of all the hypertensive disorders of pregnancy and is a major cause of fetal and maternal morbidity and mortality. Unfortunately, distinguishing between preeclampsia and other causes of hypertension on clinical grounds can be difficult because of the lack of specific tests for differential diagnosis. Increased vascular resistance has been claimed as the primary cause of preeclampsia; however, a variable hemodynamic profile with relatively high cardiac outputs, normal filling pressures, and inappropriately high systemic vascular resistances is now reported by most investigators. Imbalance between vasodilator and vasoconstrictor eicosanoids may account for platelet activation and increased responsiveness to pressor peptides. Altered prostacyclin (PGI2) to thromboxane A2 (TxA2) ratio in maternal uteroplacental vascular bed may favor local platelet activation and vasoconstriction contributing to placental insufficiency and fetal distress. Alternatively, recent evidence seems to suggest that fetal umbilical placental circulation may be the site of the primary vascular injury. Whether low-dose aspirin prevents preeclampsia because it inhibits the excessive maternal TxA2 or whether the partial inhibition of fetal TxA2 is also of therapeutic value remains to be established. Treatment of severe hypertension in pregnancy is probably important to prevent cardiac failure or cerebrovascular accidents in the mother. The need for pharmacological therapy of mild to moderate hypertension is still debated, since no formal studies are available to clarify whether pharmacological treatment in such instances effectively reduces maternal or fetal risk. For the treatment of preeclampsia, hydralazine and nifedipine may be used when delivery is not applicable. Labetalol and diazoxide are effective for hypertensive emergencies. Life-threatening hypertension that does not respond to more conventional therapy is an indication for the use of sodium nitroprusside. For chronic hypertension, alpha-methyldopa remains the treatment of choice; if ineffective, hydralazine or beta-blockers are suitable. Effectiveness and safety of other molecules remain elusive.
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PMID:Prevention and treatment of pregnancy-associated hypertension: what have we learned in the last 10 years? 188 20

Intravenous labetalol was evaluated in 10 patients with stable angina without heart failure. Mean dose was 1.75 mg/kg (range 1.5-2 mg/kg). Measurements were taken within one minute after the injection, and at 1, 5 and 15 minutes thereafter. Labetalol significantly decreased blood pressure and increased heart rate. Peak aortic flow velocity increased only significantly at 1 minute; dP/dt+ max. was significantly decreased during all the measurements. Left ventricular end diastolic pressure did not change. Thus in patients without failure left ventricular function remained stable despite the negative inotropic effects of labetalol.
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PMID:Evaluation of the alpha and beta blocking effects of intravenous labetalol on left ventricular function in coronary artery disease. 299 29

The purpose of this study was to investigate the efficacy and safety of labetalol, an alpha and beta-adrenergic receptor blocking agent in 32 patients aged from 72 to 97 years (mean = 85 years) with blood pressure (B.P.) greater than or equal to 160/95 mmHg. This study was carried out in a double-blind, randomized, placebo-controlled design. After 6 weeks of treatment with labetalol (mean dose = 235 +/- 47.5 mg/day), the systolic pressure was lowered from 187 +/- 24 to 145 +/- 28 mmHg (p less than 0.001) and the diastolic pressure from 98 +/- 10 to 82 +/- 9 mmHg (p less than 0.001). Likewise, in the placebo group, both systolic and diastolic pressures were significantly reduced but the changes were significantly greater in the labetalol group, -33 +/- 26 versus -13 +/- 20 mmHg and -14 +/- 10 versus -8 +/- 14 mmHg respectively. Labetalol achieved B.P. control (160/95 mmHg) in 64% of the treated patients, compared to 40% in the placebo group. Two patients on labetalol discontinued their treatment due to side-effects (one bradycardia and one cutaneous reaction) compared with one patient on placebo (cardiac failure). Two other cases in the labetalol group had side-effects (one fatigue and one dizziness) which prevented increasing the treatment as necessary.
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PMID:[Arterial hypertension in the elderly. Double-blind study versus placebo of the efficacy and tolerability of an alpha-beta blocker: labetalol]. 382 57

Both beta- and alpha-adrenergic mechanisms are important in the control of blood pressure; alpha-mediated vasoconstriction is responsible for the regulation of vascular tone, and beta-mediated responses stimulate the heart directly and indirectly by liberating renin and affecting vascular smooth muscle tone. beta-Adrenergic blocking drugs have long been established in the treatment of hypertension. The development of drugs which combine this action with an alpha-blocking effect represents an additional mode of action to lower the blood pressure. Numerous studies have demonstrated that labetalol intravenously or orally gives a rapid fall of blood pressure in essential and renal hypertension. It has also been used intravenously in phaeochromocytoma, tetanus, clonidine withdrawal, and as an adjunct to halothane to produce hypotensive anaesthesia. Intravenously, labetalol is probably best given as a graded infusion or as repeated small bolus injections to assure a smooth fall of blood pressure. Many long term studies have shown it to be effective orally in prolonged treatment of hypertension with studies of over 5 years, showing that tolerance does not develop. Labetalol can be used in combination with diuretics and other drugs when necessary. It can be employed to control the blood pressure in all grades of hypertension. A dosage of 100mg twice daily will often be adequate to control mild hypertension and the use of even lower doses has been reported. However, the dosage can be markedly increased in severe hypertension and while such doses are relatively exceptional, several trials have employed over 2 g per day for the more resistant cases. Studies have demonstrated that blood pressure control with labetalol is equivalent to that with beta-adrenoceptor blocking drugs plus vasodilators, or methyldopa. Labetalol has been used in patients with severe renal impairment and a number of studies suggest that it may now be the drug of choice in raised blood pressure of pregnancy. Side effects can be divided into those related to beta-blockade, those related to alpha-blockade and those not clearly related to either effect. It has been suggested that the side effects attributable to the beta-blocking component are less obtrusive than those seen with pure beta-blocking drugs without alpha-activity because the alpha-blockade modifies the consequences of beta-blockade. Heart failure has been reported, but for haemodynamic reasons would be expected to be less common; careful patient selection should avoid any risk. Similarly labetalol may worsen asthma even if the risks are probably less than with non-selective beta-blockade alone.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Combined alpha- and beta-receptor inhibition in the treatment of hypertension. 615 91

Labetalol is a combined alpha- and beta-adrenoceptor blocking agent for oral and intravenous use in the treatment of hypertension. It is a nonselective antagonist at beta-adrenoceptors and a competitive antagonist of postsynaptic alpha 1-adrenoceptors. Labetalol is more potent at beta that at alpha 1 adrenoceptors in man; the ratio of beta-alpha antagonism is 3:1 after oral and 6.9:1 after intravenous administration. Labetalol is readily absorbed in man after oral administration, but the drug, which is lipid soluble, undergoes considerable hepatic first-pass metabolism and has an absolute bioavailability of approximately 25%. There are no active metabolites, and the elimination half-life of the drug is approximately 6 hours. Unlike conventional beta-adrenoceptor blocking drugs without intrinsic sympathomimetic activity, labetalol, when given acutely, produces a decrease in peripheral vascular resistance and blood pressure with little alteration in heart rate or cardiac output. However, like conventional beta-blockers, labetalol may influence the renin-angiotensin-aldosterone system and respiratory function. Clinical studies have shown that the antihypertensive efficacy of labetalol is superior to placebo and to diuretic therapy and is at least comparable to that of conventional beta-blockers, methyldopa, clonidine and various adrenergic neuronal blockers. Labetalol administered alone or with a diuretic is often effective when other antihypertensive regimens have failed. Studies have shown that labetalol is effective in the treatment of essential hypertension, renal hypertension, pheochromocytoma, pregnancy hypertension and hypertensive emergencies. In addition, preliminary studies indicate that labetalol may be of value in the management of ischemic heart disease. The most troublesome side effect of labetalol therapy is posture-related dizziness. Other reported side effects of the drug include gastrointestinal disturbances, tiredness, headache, scalp tingling, skin rashes, urinary retention and impotence. Side effects related to the beta-adrenoceptor blocking effect of labetalol, including asthma, heart failure and Raynaud's phenomenon, have been reported in rare instances.
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PMID:Labetalol: a review of its pharmacology, pharmacokinetics, clinical uses and adverse effects. 631 May 29

The haemodynamic consequences of combined alpha- and beta-adrenoceptor blockade with intravenous labetalol were evaluated in 21 males with either high (n = 6), normal (n = 9) or low (n = 6) systemic arterial pressure, 4-17 hours after acute myocardial infarction without heart failure. Labetalol 190 +/- 18 mg (range 62-300 mg) infusion resulted in dose-related falls in systolic (P less than 0.01) and diastolic (P less than 0.05) arterial pressure in all patients. The rate of pressure reduction per mg of infused labetalol was directly proportional to the control systolic arterial pressure. Cardiac output (thermodilution) was reduced (P less than 0.05) with low dose labetalol (39 +/- 5 mg) without change on continued infusion. Left heart filling pressure (pulmonary artery occluded pressure) was unchanged throughout infusion in all patients. In conclusion, the vasodilating properties of labetalol appeared to offset the beta-blocker induced depression of cardiac function. The increased sensitivity to the effects of labetalol in those patients with hypertension may be related to excessive alpha-adrenoceptor mediated vasoconstriction in this patient group.
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PMID:Haemodynamic dose-response effects of intravenous labetalol in acute myocardial infarction. 664 15

Labetalol was used to treat systemic hypertension (systolic blood pressure above 150 mmHg) in 11 patients with acute myocardial infarction; its haemodynamic effects and tolerance were studied. Increasing doses of labetalol were infused to lower systolic blood pressure to less than 130 mmHg; the optimal rate was then maintained for one hour (mean rate: 2.3 mg/min). Haemodynamic variables were measured before, during, and after labetalol infusion. Labetalol lowered blood pressure in all patients; this effect was related to a decrease both in total systemic resistance (17.7 to 14 IU) and in cardiac index (3.1 to 2.7 1/min per m2); the stroke index remained unchanged and the heart rate was reduced (94 to 81 beats/min). There was no significant change in the mean pulmonary wedge pressure; it was decreased, however, in the six patients with an initial pressure greater than 15 mmHg. The double product was greatly decreased (16 497 to 8598 mmHg x beats per min), which is favourable in acute myocardial infarction. We conclude that labetalol is a drug of choice to treat hypertension in acute myocardial infarction because it is very effective; its haemodynamic effects are likely to reduce myocardial oxygen requirements and suggest that labetalol administration does not worsen moderate left sided heart failure. The drug, however, may reduce the cardiac output.
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PMID:Treatment of hypertension in acute stage of myocardial infarction. Haemodynamic effects of labetalol. 684 14

Five patients with malignant arterial hypertension and terminal (3) or advanced (2) renal failure were treated with the alpha-beta blocker labetalol and the angiotensin-converting enzyme inhibitor captopril. Labetalol alone or in combination with other antihypertensive agents had been ineffective in two cases and captopril alone in one; yet hypertension was rapidly controlled when the two drugs were given together. The return of blood pressure to normal levels brought about regression of digitalis-resistant cardiac failure in 2 patients and slight improvement of renal function in 2 other patients. The captopril-labetalol combination probably has a synergistic effect, and although its mechanism remains obscure this effect may be used to treat patients with severe or malignant arterial hypertension.
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PMID:[Combined captopril and labetalol treatment of malignant arterial hypertension (author's transl)]. 702 48

beta-adrenoceptor-blocking drugs, first introduced for the treatment of symptomatic angina pectoris, have been found effective across the whole spectrum of ischaemic disease. Labetalol was the first combined-action beta-blocking drug to be described and was shown to be capable of increasing exercise tolerance in patients with angina pectoris. Carvedilol also possesses a peripheral vasodilating action mainly due to an alpha 1-adrenoceptor blockade. Haemodynamic studies with carvedilol in patients with ischaemic heart disease have shown a reduction in peripheral vascular resistance in contrast to propranolol which increases systemic resistance and reduces cardiac output. Additionally, in ischaemic heart failure there is evidence of improved myocardial function, as shown by an increase in ejection fraction, after the administration of carvedilol. Carvedilol has been shown to improve exercise tolerance in patients with angina pectoris and reduce the occurrence of episodes of silent myocardial ischaemia. Carvedilol, unlike many beta-blocking drugs, does not adversely affect the plasma lipid profile qualitatively or quantitatively. In contrast to many non-selective beta-blocking drugs, carvedilol has a more favourable haemodynamic profile, and its lack of adverse influence on the plasma lipid profile may be important in its long-term use.
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PMID:Carvedilol in ischaemic heart disease. 810 63


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