A pharmacoepidemiological evaluation of anticholinergic prescribing patterns in the elderly

The elderly are high consumers of both prescription and over-the-counter medications. As a result of age-related changes in drug pharmacokinetics and pharmacodynamics, they experience twice the number of adverse effects than in the general population. Using the health insurance data bases of the province of Saskatchewan, the prescribing pattern of drugs which have anticholinergic properties, was studied in the elderly. Of patients less than or equal to (< or =) 64 years of age 3.8% compared to 11.3% of patients greater than or equal to (> or =) 65 years of age were prescribed an anticholinergic medication. In the elderly group, 9.3% of the ambulatory subjects and 43.8% of the special care home (SCH) residents received a prescription for an anticholinergic drug. The concurrent prescribing of two or more anticholinergic medications was also higher in the elderly (0.16% of patients < or = 64 versus 0.54% of patients > or = 65). All differences between patients < or = 64 and those > or = 65, as well as between the ambulatory elderly subjects and the SCH elderly residents, were statistically significant. Approximately 25% of all anticholinergic medications were prescribed in the high to excessive dosage range. The study also looked at prescribing patterns for individuals with a diagnosis of dementia. Despite the potential detrimental adverse effect of anticholinergic therapy in that patient group, 35.5% received a prescription for anticholinergic medication. These data confirm that the elderly are at high risk for receiving a prescription for anticholinergic medications. The high prevalence of anticholinergic prescribing in a patient population known to be sensitive to anticholinergic side-effects has the potential to cause significant adverse clinical consequences.