Definition of Drug-Induced Cognitive Impairment in the Elderly

Donna M. Lisi, PharmD, BCPS, BCPP, CGP, FASCP


June 14, 2000

In This Article


Drug-induced cognitive impairment can generally be categorized into 2 types: delirium and dementia. Drug-induced delirium refers to the development of an acute confusional state, whereas drug-induced dementia implies a more chronic alteration in mental function.[1] Drug-induced cognitive impairment is the most common reversible cause of confusion.[2] It can be either dose related or, in some cases of delirium, it may be idiosyncratic. Cognitive impairment secondary to nonpsychoactive medications may be more likely to result from an idiosyncratic mechanism. Compared with drug-induced delirium, less is known about the prevalence of drug-induced dementia.[1]

Nearly every drug class can cause either drug-induced delirium or dementia in older persons. The elderly may be especially prone to developing drug-induced cognitive impairment due to age-related changes in drug pharmacokinetics (eg, reduced oxidative metabolism, reduced renal function) and pharmacodynamics. The elderly may also be at greater risk of drug-induced confusion than younger people because of decreased functional reserve of the CNS and changes in brain perfusion. They may have alterations in neurotransmitter systems. Alzheimer's disease and vascular dementia are more common in this age group; dementia is a major predisposing risk factor for the development of drug-induced cognitive impairment. Polypharmacy, involving both prescription and over-the-counter medications, is also very common among the elderly and increases the risk of cognitive impairment. Electrolyte imbalances, which occur frequently in older persons, can predispose to cognitive changes.


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