Objective: Reduction in anticholinergic burden in the elderly is associated with improved behavioral and cognitive function. In vitro, some atypical antipsychotics have high, while others have little or no affinity for muscarinic receptors. Their increasing use in older patients mandates studies to ensure their safety in this sensitive population.
Design: Subjects were ³55 years old with dementia, MMSE score 7-26, and hallucinations/delusions disruptive to care. They were randomized to risperidone (0.75-1.5 mg/d) or olanzapine (5-10 mg/d) for 6 weeks.
Materials and Methods: Anticholinergic activity (pmol/mL atropine equivalents by radioreceptor assay) was measured at baseline after 3 and 6 weeks of treatment.
Results: Anticholinergic activity data were available for 48 (n=23 risperidone; n=25 olanzapine) of 86 randomized subjects (75.0% females; mean ±SD age, 84.5±7.18). There was no significant change in mean anticholinergic activity at any time point in the risperidone group (3.32 at baseline, 4.16 at week 3, 3.91 at endpoint; p=0.230); it increased significantly at all time points in the olanzapine group (2.23 at baseline, 3.59 at week 3, 3.64 at endpoint; p=0.003). Between-group differences were not significant (0.05 levels).
Conclusion: These results are consistent with in vitro binding studies. Next steps include studying the impact of cholinergic burden on clinical and functional outcomes.
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