Comparison of rates of potentially inappropriate medication use according to the Zhan criteria for VA versus private sector medicare HMOs.

Background: Inappropriate prescribing in the elderly is common, but rates across different health care systems and the impact of formulary restrictions are not well described.

Objective: To determine if rates of inappropriate medication use in the elderly differ between the Veterans Affairs (VA) health care system and the private sector Medicare health maintenance organization (HMO) patients.

Methods: A cross-sectional study design compared administrative pharmacy claims from 10 distinct geographic regions in the United States in the VA health care system and 10 analogous regions for patients enrolled in Medicare HMOs.