The effect of a single low dose of trihexyphenidyl on memory functioning in the healthy elderly

Medications with anticholinergic properties, when taken at therapeutic doses, are known to adversely affect memory functioning in young adults and the elderly. However, their impact at lower doses in geriatric persons has been less thoroughly studied. We investigated the impact of a single 2-mg dose of trihexyphenidyl on memory functioning in 20 healthy elderly subjects using a within-subjects, double-blind comparison with a placebo. Memory functioning was evaluated using subtests of the Wechsler Memory Scale. Subjects also rated the perceived impact of medication on their performance following memory testing. Results indicated that the single 2-mg dose of trihexyphenidyl produced impaired performance on measures of immediate and half-hour delayed recall of complex verbal and visual material when compared to the placebo condition. However, differences were not found on several other memory measures, including general orientation, attention-concentration, and learning of word associations. The significance of these selective memory deficits and suggestions regarding future research are discussed.