Beta-blocker are drugs that block the transmission of certain nerve impulses and are used to treat disorders of the heart and circulation.
Beta-blocker drugs, or beta-adrenergic blocking agents, are widely prescribed to treat disorders of the heart and circulation and also to treat other conditions. Cardioselective beta-blockers act mainly on the heart. Other beta-blockers act on blood vessels throughout the body and on other target tissues such as the cells that secrete fluid in the eye.
Why are beta-blocker drugs used?
Beta-blockers are most commonly used to treat high blood pressure (see Hypertension). They are also used to treat heart disorders, including angina, a disabling chest pain caused by too little oxygen reaching the heart muscle; in the treatment of heart failure (see Chronic heart failure); to prevent the recurrence of a heart attack (see Myocardial infarction); and to correct some irregularities of heart rhythm (see Arrhythmias). Beta-blockers are used to treat or prevent other conditions, such as recurrent migraine, which is thought to be caused by constriction and rebound widening of blood vessels in the head. They are also used for glaucoma, in which pressure in the eye is increased by a build-up of excess fluid. Some beta-blockers are used to control physical symptoms of anxiety, such as tremor. The drugs also help in the treatment of hyperthyroidism by reducing the symptoms caused by the excess production of thyroid hormone, such as sweating, tremor, and rapid heart rate.
How do beta-blocker drugs work?
Beta-blockers work by blocking the action of epinephrine (adrenaline) and norepinephrine (noradrenaline), two chemicals produced by the body that increase heart rate and raise the blood pressure. Cardioselective beta-blockers are especially effective at slowing heart rate and reducing the force of the heartbeat, thereby reducing the workload of the heart. These actions make beta-blockers effective in the treatment of angina, hypertension, and some types of arrhythmia. Other beta-blockers have a more widespread action and block many of the effects that norepinephrine has throughout the body, such as narrowing blood vessels and causing tremor and sweating. As a result, they may be effective in treating some physical symptoms caused by this chemical, such as tremor. Beta-blockers do not treat the underlying causes of these conditions.
Beta-blockers are used for migraine because they block the effects of nor-epinephrine on blood vessels in the head. They also reduce fluid formation, and thus pressure, in the eyeball, and so are used to treat glaucoma.
How are beta-blocker drugs used?
If you have angina, high blood pressure, or recurrent migraine, you may be given long-term treatment with oral beta-blockers. Your doctor may initially prescribe a low dose and increase it until the desired effect is reached. If you have glaucoma, you may be prescribed eyedrops that contain the beta-blocker timolol. A beta-blocker may be given intravenously in hospital if you experience sudden severe angina or if you have a heart attack.
Beta-blockers are also used along with other types of drug, especially in the treatment of angina, high blood pressure, and some types of heart failure.
What are the side effects of beta-blocker drugs?
Beta-blockers can exacerbate some respiratory disorders and are not normally given to people who have a history of chronic obstructive pulmonary disease or asthma. However, if treatment with these drugs is necessary, cardioselective beta-blockers can sometimes be used. Since beta-blockers can mask some of the symptoms of hypoglycaemia (low blood glucose), which is a serious condition that must be recognized and treated immediately, they may not be suitable for people who need to take insulin for diabetes mellitus. If you are taking a beta-blocker, your sleeping pattern may be disrupted, and your hands and feet may feel cold because the blood circulation in the extremities is reduced. Men sometimes experience erectile dysfunction, but normal sexual function usually returns when the drug is stopped. Rarely, beta-blockers cause rashes and dry eyes. All these side effects tend to be more common and more severe in elderly people. If you need to stop taking a beta-blocker, your doctor will advise you on how to reduce the dose gradually to avoid rebound high blood pressure, a recurrence of angina, or a heart attack.
Do not suddenly stop taking a beta-blocker drug without consulting your doctor. Abrupt withdrawal of the drug could cause a rise in blood pressure, worsening of angina, or an increased risk of a heart attack.
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