Beta blocker:A class of drugs that block the effect of beta-adrenergic substances such asadrenaline(epinephrine), that play a key roleinthe sympathetic portion of theinvoluntarynervous system. By blocking the action of thesympathetic nervous systemon the heart, they slow the heartbeat and relieve stress on the heart.Beta blockersare used to treat abnormal heart rhythms, specifically to prevent abnormally fast heart rates (tachycardias) or irregular heart rhythms, such as prematureventricularbeats. Because beta blockers reduce the demand of theheart muscleforoxygen, they can be useful in treating angina. They have also become important drugs in improving survival after a heart attack. Due to their effect onbloodvessels, beta blockers can lower theblood pressureand are of value in the treatment of hypertension. Other uses include the prevention of migraine headaches and the treatment offamilialor hereditaryessentialtremors. Beta blockers reduce pressure within theeyeand they are therefore used to lessen the risk of damage to theoptic nerveand loss of vision in patients with glaucoma. Beta blockers include acebutolol (Sectral),atenolol(Tenormin),bisoprolol(Zebeta), metoprol (brand names:Lopressor, Lopressor LA,Toprol XL),nadolol(Corgard), andtimolol(Blocadren).Topicalbeta blockers for the eye include timololophthalmicsolution (Timoptic) and betaxolol hydrochloride (Betoptic).
