fniernatioMi Psychogeriarrics, Voi. 4, No. 2,1992 0 1992 Springer Publishing Company The Effect of a Single Low Dose of Trihexyphenidyl on Memory Functioning in the Healthy Elderly Bharat Raj S. Nakra, Ronald B. Margolis, Jeffrey D. Gfeller, George T. Grossberg, and Lindbergh S. Sata ABSTRACT. Medications with anticholinergic properties, when taken at therapeuticdoses, are known to adverselyaffect memory functioning in young adultsand the elderly. However,their impact at lower doses in geriamc persons has been less thoroughly studied. We investigatedthe impact of a single2-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. Subjectsalso rated the perceived impact of medication on their performance following memory testing. Results indicated that the single 2-mg dose of mhexyphenidyl produced impaired performanceon measures of immediate and half-hour delayed recall of complex verbal and visual material when comparedto the placebocondition. 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 sugges- tions regarding future research are discussed. Medications with anticholinergic properties are frequently prescribed to elderly persons for a variety of medical disorders, including Parkinsonism, peptic ulcer, and urinary incontinence. Many psychoactive drugs (e.g., thioridazine and amitriptylene) have potent anticholinergic side effects as well. In addition, many over-the-counter drugs available for insomnia and colds, used frequently by the elderly, have anticholinergic effects. A number of clinical studies of patients with Parkinsonism (Sadeh et al., 1982; Syndulkoet al., 198 l), patients with Alzheimer’sdisease (Sunderlandet al., 1988), From the Department of Psychiatry and HumanBehavior, St. Louis University School of Medicine, St. Louis, Missouri, U.S.A. @. R. S. Nakra, MD, MRCPsych; R. B. Margolis, PhD J. D. Gfeller, PhD G. T. Grossberg. MD; and L. S. Sata, MD). New affiliation: Department of Psychiatry, 207 Washington School of Medicine, St. Louis, Missouri (B.R.S. Nakra, MD. MRCPsych).