Beta blockers prevention

BETA-BLOCKERS ALPHA-BLOCKERS t efficacy of alpha-blockers t risk of first-dose 1 BP with alfuzosin, prazosin and terazosin Additive hypotensive effect may be used therapeutically. Beta-blockers prevent the ability to mount a tachycardia in response to 1 BP this T the risk of first-dose 1 BP when starting alpha-blockers in patients already on beta-blockers Monitor BP at least weekly until stable watch for first-dose 1 BP. Warn patients to report symptoms of hypotension (light-headedness, dizziness on standing, etc.)... 

Beta blockers prevent cAMP formation, with primary effects on SA and AV nodal tissues. 

In the treatment of hypertension, a major use of beta-blockers is in combination with hydralazine. The direct vasodilators bring about reflex cardiac stimulation, and beta-blockers prevent these adverse effects (see also Figure 67). Beta-blockers also reduce blood pressure by exerting a central effect or a peripheral action, or both, which decreases renin activity. Metoprolol and atenolol are beta selective, and they are safer agents in patients with asthma, diabetes mellitus, or low-renin hypertension. Some beta-blocking agents such as pindolol have intrinsic sympathomimetic activity and may be used in the treatment of pronounced bradycardia (sick sinus syndrome). Unlike propranolol, metoprolol is not a very lipid-soluble... 

Beta-adrenoceptor antagonists are used in the treatment of hyperthyroidism to alleviate symptoms but are not considered to influence thyroid hormone production nor the effect of the hormone on cell function. A study of the effect of beta-blockers on lymphocyte metabolism was done with the purpose to clarify their mechanism of action in hyperthyroidism [68]. When hyperthyroid subjects were treated with beta-blockers, lymphocyte heat production was found to be within normal limits, thus showing that beta-blockers prevent the expected increased of cell metabolism under stimulation of thyroid hormone. These results seem to indicate that increased thermogenesis in hyperthyroidism is mediated via adrenergic receptors, rather than via nuclear thyroid hormone receptors. 

On the basis of two large randomized trials aimed at suppressing premature ventricular complexes after MI, so-called warning arrhythmias, it was discovered that many common antiarrhythmic medications actually increase the risk of mortality [20, 21]. Amiodarone also has been shown to have no definitive effect on mortality in patients after an MI, including in the recent SCD-HeFT trial [22-24]. In fact, of all antiarrhythmic medications, only beta blockers have been clearly shown to prevent SCD after MI [25], particularly among those with depressed LV function [11]. 

Because the above trials showed a >50% relative reduction in total mortality with ICD therapy, MADIT II used broader entry criteria for primary prevention of SCD, removing the criteria for NSVT and EPS 1,232 patients with a history of MI > 30 days prior and an EF < 30% were randomized to conventional therapy or ICD implantation [10]. Conventional therapy was comparable in both arms and included a high rate of use of beta blockers, angiotensin-converting enzyme inhibitors, and statins (over two thirds for all medications in both arms). The trial was stopped early at 20 months because the relative reduction in total mortality... 

Connolly SJ, Dorian P, Roberts RS, Gent M, Bailin S, Fain ES et al. Comparison of beta-blockers, amiodarone plus beta-blockers, or sotalol for prevention of shocks from implantable cardioverter defibrillators the OPTIC Study a randomized trial. JAMA 2006 295 165-71. 

Eor preventive treatments, the adverse effects of the beta blockers are classical for this class bradycardia, bronchospasm, hypotension, nightmares and depression. Indoramine induces neuropsychiatric effects (sedation, asthenia) and cardiovascular disorders (hypotension). Eluanarizine is strictly contraindicated in patients with Parkinsonism and depression. 

Must be used in conjunction with diuretic (except dialysis patients) and beta-blocker or other sympathetic nervous system depressant (to prevent reflex tachycardia)... 

Oral minoxidil administration should be closely monitored, usually given with a beta-blocker to prevent tachycardia and a diureticto prevent fluid accumulation. 

Propranolol was the first blocker shown to be effective in hypertension and ischemic heart disease. Propranolol has now been largely replaced by cardioselective blockers such as metoprolol and atenolol. All B-adrenoceptor-blocking agents are useful for lowering blood pressure in mild to moderate hypertension. In severe hypertension, blockers are especially useful in preventing the reflex tachycardia that often results from treatment with direct vasodilators. Beta blockers have been shown to reduce mortality after a myocardial infarction and some also reduce mortality in patients with heart failure they are particularly advantageous for treating hypertension in patients with these conditions (see Chapter 13). 

Bangalore S et al Beta-blockers for primary prevention of heart failure in patients with hypertension Insights from a meta-analysis. J Am Coll Cardiol 2008 52 1062. [PMID 18848139]... 

People with diabetes have a much worse outcome after acute myocardial infarction, with a mortality rate at least twice that in non-diabetics. However, tight control of blood glucose, with immediate intensive insulin treatment during the peri-infarct period followed by intensive subcutaneous insulin treatment, was associated with a 30% reduction in mortality at 1 year, as reported in the DIGAMI study. In addition, the use of beta-blockers in this group of patients had an independent secondary preventive effect (198). The use of beta-blockers in diabetics with ischemic heart disease should be encouraged (199). 

Samuelsson O, Hedner T, Berglund G, Persson B, Andersson OK, Wilhelmsen L. Diabetes mellitus in treated hypertension incidence, predictive factors and the impact of non-selective beta-blockers and thiazide diuretics during 15 years treatment of middle-aged hypertensive men in the Primary Prevention Trial Goteborg, Sweden. J Hum Hypertens 1994 8(4) 257-63. 

Metoprolol (Lopressor, Toprol-XL). Metoprolol is considered a cardioselective beta blocker and has been approved for treating hypertension, preventing angina pectoris, and preventing myocardial reinfarction. As an antihypertensive and antianginal, metoprolol is usually administered orally. In the prevention of reinfarction, metoprolol is initiated by intravenous injection and then followed up by oral administration. 

Propranolol [Inderal). Propranolol, the classic nonselective beta blocker, is approved for use in hypertension, angina pectoris, cardiac arrhythmias, and prevention of myocardial reinfarction. In addition, propranolol has been used in the prevention of vascular headache and as an adjunct to alpha blockers in treating pheochromocytoma. Propranolol is usually administered orally for the long-term management of the previously listed conditions, but it may be administered via intravenous injection for the immediate control of arrhythmias. 

Timolol CBlocadren). This nonselective beta blocker is administered orally for the treatment of hypertension and prevention of myocardial reinfarction. It may also be used to treat angina or prevent vascular headaches. 

Alpha-adrenergic antagonists are used primarily as antihypertensive drugs because of their ability to block vascular alpha-1 receptors. Beta-adrenergic antagonists (beta blockers) are administered primarily for their inhibitory effects on myocardial function and are used in the prevention and treatment of hypertension, angina pectoris, arrhythmias, and myocardial reinfarction. Many of the drugs introduced in this chapter are discussed further in chapters that deal with the specific clinical conditions (e.g., hypertension, asthma, and other disorders). 

Consequently, beta blockers are given to certain patients with angina to limit the oxygen demands of the heart.12,31 This prophylactic administration prevents the onset of an anginal attack. The use of beta blockers in specific forms of angina is reviewed later in this chapter. 

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