Chapter 32

In developed countries, the population is aging steadily. In the United States, those older than 65 years of age comprise not only an increasing proportion of the population at large (12%) but also an increasing proportion of patients seen in medical practices. Compared with all other age groups, patients older than 65 years of age account for one-third of emergency department (ED) ambulance arrivals and the highest proportion of patients in EDs triaged as emergent.80

Although the elderly account for only a small minority of toxicologic exposures, after they have been exposed, they have a high mortality rate. Among exposures reported to the American Association of Poison Control Centers (AAPCC) in 2006, the fatality ratio (ie, number of cases divided by number of deaths) increased with age in a bimodal pattern, with peaks in the middle and latest decades of life (see Chap. 135). Previous AAPCC surveys had shown a steady increase in fatality ratio. In addition to possible methodologic changes and smaller numbers of exposures in the latest decades of life, potential explanations for the current change to a bimodal pattern may include an increase in intentional exposures in midlife and physiologic vulnerability in the later decades. However, this only accounts for part of the difference because suicide fatality ratios increase steadily with age (see Suicide and Intentional Poisonings below). In a separate study, seven specific pharmaceuticals were selected from the AAPCC database for analysis based on their prevalent use and potential toxicity from 1995 through 2002. These pharmaceuticals were theophylline, digoxin, benzodiazepines, tricyclic antidepressants (TCAs), calcium channel blockers, acetaminophen, and salicylate.97 The death rate from intentional or unintentional exposure to these pharmaceuticals was found to increase by 35% for each decade of life after age 19 years.97

Toxic exposures reported to the AAPCC may underestimate the serious consequences for elderly people exposed to toxic substances. Data from the National Electronic Injury Surveillance System—Cooperative Adverse Drug Event Surveillance Project (NEISS-CADES) indicate that patients aged 65 years and older accounted for 25% of estimated visits related to adverse drug events (ADEs) and almost 50% of such visits requiring hospitalization or prolonged monitoring in the ED.10 The problem may be even greater because the NEISS-CADES study did not capture recognized or unrecognized ADEs in patients treated or dying outside of EDs.

Underrecognition of toxic exposures in the elderly may occur for several reasons. First, because of pharmacokinetic and pharmacodynamic changes that occur as one ages,31 a "standard" therapeutic dose may produce an unexpected serious effect. Second, the presentation of disease, including drug toxicity, is often atypical in the elderly.59 For example, falls in the elderly may be a presenting sign of xenobiotic toxicity and are commonly due to prescribed xenobiotics, with sedative–hypnotics, antipsychotics, antidepressants, and class Ia antidysrhythmics (quinidine and procainamide) most often associated with an increased risk of falling.108 If the patient is cognitively impaired and the fall is ...

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