Beta Blocker Medications
A beta-blocker or β-blocker is a drug used in cardiology, which blocks the action of the adrenergic system mediators such as adrenaline. Beta-blockers take the place of these mediators on receptor β but does not cause reaction from the receiver, or a reaction as strong as it had been a mediator. Some β-blockers prevent the occurrence of adrenergic mediators and indirectly oppose their actions.
Effects of β-blockers
On the β-1 receptors
* Reduction in heart rate (negative chronotropic effect)
* Decreased cardiac excitability (bathmotrope negative effect)
* Decreased myocardial contractility (negative inotropic)
* Decreased conduction velocity (negative dromotropic effect)
* Reduced production of renin
On the β-2 receptors
* Limiting the constriction of smooth muscle cells of the lung and uterus
List of β-blockers
They block receptors preferentially β-1 cardiac they therefore reduced vasoconstriction, bronchoconstriction, and decrease the risk of hypoglycemia.
Beta-blockers are used in the treatment of angina bottom to prevent the onset of angina attacks. After myocardial infarction, they reduce significantly the risk of recurrence and the risk of ventricular arrhythmia to prevent a number of sudden death.
They are also used to stabilize high blood pressure or treat a hypertensive crisis. The threshold on the heart is reduced to prevent excessive cardiac stress. Blood pressure is reduced by a lower rate and steady.
They are also used as an antiarrhythmic drug and is the Class II classification of Vaughan Williams. They are effective in slowing a rapid pace and to prevent the occurrence of an arrhythmia or ventricular fibrillation.
The use in heart failure is more recent. It is somewhat paradoxical because they decrease the contraction of heart muscle and counteract the effect of adrenergic system, useful for maintaining cardiac output. The first use date of 1975. Their effectiveness is now widely demonstrated both in reducing mortality and serious adverse events.
Beta-blockers without intrinsic sympathomimetic activity can also be used for prophylaxis of migraine refractory to treatment. Propranolol, nadolol, atenolol and metoprolol are all proven effective in reducing the number but also the severity of crises. By comparison, the antagonists with intrinsic sympathomimetic activity (alprenolol, oxprenolol, pindolol and acebutolol) do not offer such protection.
They are also effective in the treatment of hyperthyroidism, drug withdrawal, prevention of gastrointestinal bleeding in cirrhotic patients with oesophageal varices, in case of earthquakes (they are considered as doping in sports precision), in certain parkinsonism and akathisia in some glaucoma.
All beta-blockers are equally effective in all situations, or because their characteristics are different, or that the company that makes the molecule have not found it useful to test it in all situations.
Adverse effects of β-blockers
* Vasoconstriction of peripheral vessels and Raynaud's phenomenon (poor blood flow to the extremities)
* Crisis asthma (bronchospasm)
* Pulmonary edema
* Angina pectoris in Prinzmetal's angina
* Nightmares, insomnia, fatigue
* Low blood pressure (in the use of β-blocker non-cardioselective): hypotension due to bradycardia. The patient described a sensation of blockage in the effort and a weakness. He finds an increased fatigue and shortness of breath.
* Worsening of lesions of psoriasis
* Rare: induced lupus (1st cause of induced lupus, but it is an extremely rare side effect in view of the low frequency of induced lupus)
* Complication related to compliance: It is necessary to ensure that the tablets are taken regularly, because abrupt discontinuation of treatment may be followed by serious arrhythmias, myocardial or sudden death.
* Digestive disorders, such as stomach ache, nausea, vomiting and diarrhea may appear.
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