Hypersensitivity to scopolamine in the elderly.

Scopolamine hydrobromide, 0.43 mg/70 kg, was administered by subcutaneous injection to ten young and ten elderly subjects. A comprehensive neuropsychological test battery was used to assess the effects of scopolamine, as compared to placebo, on cognitive function. As previously reported for this group of young subjects, scopolamine significantly impaired performance on tests of recent memory and visuospatial praxis. The same effects were observed in the elderly subjects, but the magnitude of the effects was much larger. The scopolamine injections produced significant psychomotor slowing in the elderly, whereas higher doses of the drug are required to produce this effect in young subjects. In both young and old subjects scopolamine failed to affect immediate memory, language function, object sorting, and the frequency of intrusion errors (although trends toward an effect were more apparent in the elderly). Remote memory, tested in the elderly only, was also unaffected. The results suggest that scopolamine's cognitive effects are quantitatively more pronounced in elderly subjects than young subjects, but that they are qualitatively similar and do not constitute a valid model for the cognitive dysfunction associated with Alzheimer's disease.