Effect of Dual Use of Veterans Affairs and Medicare Part D Drug Benefits on Antihypertensive Medication Supply in a National Cohort of Veterans with Dementia

Objective To evaluate the effect of dual use of VA/Medicare Part D drug benefits on antihypertensive medication supply in older Veterans with dementia. Data Sources/Study Setting National, linked 2007-2010 Veterans Affairs (VA) and Medicare utilization and prescription records for 50,763 dementia patients with hypertension. Study Design We used inverse probability of treatment (IPT)-weighted multinomial logistic regression to examine the association of dual prescription use with undersupply and oversupply of antihypertensives. Data Collection/Extraction Methods Veterans Affairs and Part D prescription records were used to classify patients as VA-only, Part D-only, or dual VA/Part D users of antihypertensives and summarize their antihypertensive medication supply in 2010: (1) appropriate supply of all prescribed antihypertensive classes, (2) undersupply of >= 1 class with no oversupply of another class, (3) oversupply of >= 1 class with no undersupply, or (4) both undersupply and oversupply. Principal Findings Dual prescription users were more likely than VA-only users to have undersupply only (aOR = 1.28; 95 percent CI = 1.18-1.39), oversupply only (aOR = 2.38; 95 percent CI = 2.15-2.64), and concurrent under- and oversupply (aOR = 2.89; 95 percent CI = 2.53-3.29), versus appropriate supply of all classes. Conclusions Obtaining antihypertensives through both VA and Part D was associated with increased antihypertensive under- and oversupply. Efforts to understand how best to coordinate dual-system prescription use are critically needed.