Medications used to treat glaucoma can have clinically important systemic effects in some patients; these effects may not be recognized in elderly patients who have chronic medical problems and who are taking several systemic medications. Beta-blocking ophthalmic agents are generally safe, but can be absorbed systemically to induce bronchospasm, worsen heart block, decompensate congestive heart failure, or create central nervous system effects in some patients. Reports of adverse systemic effects from miotics, such as pilocarpine, are rare, although cardiovascular decompensation has been seen in patients with acute angle closure who were given excessive doses before surgery. Topical sympathomimetic agents such as epinephrine may increase ventricular extrasystoles and have, on occasion, caused severe hypertensive reactions. Nearly 50% of patients taking carbonic anhydrase inhibitors must discontinue their use because of various adverse constitutional and central nervous system symptoms. Although these drugs are not usually part of internal medicine regimens, they can produce adverse effects that mimic primary disease in nonocular organ systems.