Beta-adrenergic–blocking agents are widely used for the treatment of hypertension, arrhythmias, angina pectoris, heart failure, migraine headaches, and glaucoma. Many patients with beta-blocker overdose will have underlying cardiovascular diseases or will be taking other cardioactive medications, both of which may aggravate beta-blocker overdose. Of particular concern are combined ingestions with calcium blockers or tricyclic antidepressants. A variety of beta blockers are available, with various pharmacologic effects and clinical uses (Table II–15).