The concurrent use of anticholinergics and cholinesterase inhibitors: rare event or common practice?

OBJECTIVES: To measure the prevalence of anticholinergic use cross-sectionally in patients receiving cholinesterase inhibitors and to describe change in use of anticholinergics upon inception of cholinesterase inhibitor treatment.
DESIGN: Cross-sectional and inception cohort studies.
SETTING: State of Iowa. PARTICIPANTS: Iowa Medicaid beneficiaries aged 50 and older with a pharmacy claim for a cholinesterase inhibitor during January 1997 through February 2000. MEASUREMENTS: Anticholinergic use was determined for all patients with a cholinesterase inhibitor pharmacy claim during January and February of 2000. A frequency distribution of all anticholinergics was compiled, with emphasis placed on those considered inappropriate in the elderly. In a separate analysis, anticholinergic use was determined at two points: 90 days before and after cholinesterase inhibitor inception.
RESULTS: Of 557 patients receiving a cholinesterase inhibitor, 197 (35.4%) received an anticholinergic concurrently. Of all anticholinergics, 74.5% (178/239) had been identified as inappropriate for use in the elderly, 22.2% (53/239) under any circumstances. At the time of cholinesterase inhibitor inception, 30.2% (143/474) and 33.5% (159/474) of patients received an anticholinergic 90 days before and 90 days after inception, respectively. Increases in anticholinergic prescribing upon cholinesterase inhibitor inception exceeded decreases (Wilcoxon signed-rank test, S=529, P=.020).
CONCLUSION: The concurrent use of anticholinergics and cholinesterase inhibitors is common although rarely appropriate. Patients with Alzheimer's disease deserve to receive the optimum benefit from cholinesterase inhibitor treatment, which can only be achieved through diligent and appropriate use of concurrent pharmacotherapy.