Concomitant use of cholinesterase inhibitors and anticholinergics: prevalence and outcomes.

OBJECTIVES: To determine the extent of concomitant use of cholinesterase inhibitor (ChI) and anticholinergic (ACh) medications and the clinical consequences of dual use in a population-based setting.
DESIGN: Retrospective cohort study.
SETTING: Group Health Cooperative and Kaiser Permanente Colorado. PARTICIPANTS: Five thousand six hundred twenty-five adults aged 50 and older who began new use of a ChI between 2000 and 2007. MEASUREMENTS: Rates and characteristics of concomitant ChI and ACh use and the association between dual use and the outcomes of death and nursing home placement (claim from a nursing home with no prior claims used as a proxy).
RESULTS: Thirty-seven percent of ChI users also received AChs. Eleven percent of ChI users were concomitantly using two or more moderate to potent AChs. Median duration of this concomitant use was approximately 4 months, but a substantial proportion (25%) continued to use both medication classes simultaneously for longer than 12 months. In 23% of ChI users, AChs were being used at the time ChI therapy was initiated. The majority of this ACh use (77%) was not stopped once ChIs were started. No association was observed between concomitant use and risk of death or nursing home placement.
CONCLUSION: These results should raise awareness about the prevalence and potential inappropriateness of concomitant use of ChIs and AChs and promote evaluations of practices intended to improve care standards.