A class of drugs that block beta-adrenergic substances such
as adrenaline (epinephrine) in the "sympathetic" portion of the autonomic (involuntary)
nervous system. By blocking the action of the sympathetic nervous system on the
heart, beta blockers relieve stress on the heart; they slow the heart beat, lessen
the force with which the heart muscle contracts, and reduce blood vessel contraction
in the heart, brain, and throughout the body. Beta blockers may be used to treat
abnormal heart rhythms (cardiac arrhythmias) and prevent abnormally fast heart rates
(tachycardias) or irregular heart rhythms such as premature ventricular beats. Since
beta blockers reduce the demand of the heart muscle for oxygen and the chest pain
of angina pectoris occurs when the oxyg en demand of the heart exceeds the supply,
beta blockers can be useful in treating angina. They have also become an important
drug in improving survival after a person has had a heart attack. Thanks to their
effect on blood vessels, beta blockers can lower the blood pressure and be of value
in the treatment of hypertension. Other uses for beta blockers include the prevention
of migraine headaches and the treatment of certain types of tremors (familial or
hereditary essential tremors).
The beta blockers (with brand names) include:
acebutolol (Sectral),
atenolol (Tenormin),
bisoprolol (Zebeta),
metoprol (Lopressor, Lopressor LA, Toprol XL),
nadolol (Corgard), and
timolol (Blocadren).
Beta blockers are also available in combination with a diuretic as, for example,
with bisoprolol and hydrochlorothiazide (Ziac).
Beta blockers reduce the pressure within the eye (the intraocular pressure),
probably by reducing the production of the liquid (aqueous humor) within the eye,
and so are used to lessen the risk of damage to the optic nerve and loss of vision
in glaucoma. Beta blocker preparations for this purpose include timolol ophthalmic
solution (Timoptic) and betaxolol hydrochloride (Betopic, Betopic S).
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