Examination of multiple medication use among TRICARE beneficiaries aged 65 years and older

The simultaneous use of multiple prescription medications has been associated with an increased risk of adverse drug events and other drug-related complications, especially in the elderly. To quantify the prevalence of use of multiple medications among a sample of Department of Defense (DoD) health care beneficiaries, aged 65 years and older, who used their TRICARE (military health care services) benefit to obtain prescription medication. Outpatient pharmacy fill records were analyzed for a 10% random sample of 1.27 million TRICARE beneficiaries aged 65 years and older who obtained 1 or more prescription medications in the 90-day period from December 1, 2004, through February 28, 2005. The First DataBank generic code number was used to identify drugs and to calculate the mean number of medications obtained and the mean, frequency, and type of American Hospital Formulary System drug therapy categories. Statistical significance for gender and age subgroups was tested via independent t tests. There were 1,268,162 users of the TRICARE pharmacy benefit in the 90-day study period from December 1, 2004, through February 28, 2005, approximately 72.7% of 1,744,072 eligible beneficiaries. The 10% sample of these users (n=126,682) accounted for 1,091,699 pharmacy fill records for 761,043 unique medications, or an average of 6.01 [SD 4.01] unique medications per user, distributed across an average of 3.80 [2.08] therapeutic categories; 8.8% of users received 1 medication, 50.0% received 5 or more medications from an average of 3 therapeutic categories, and 2.8% obtained 16 or more medications from an average of 8 therapeutic categories. Multiple drug use was more prevalent among women relative to men, with an average of 6.28 [4.12] medications from 4.03 [2.11] therapeutic categories for women versus an average of 5.69 [3.85] medications from an average of 3.80 [2.08] therapeutic categories for men (P