The impact of increasing patient prescription drug cost sharing on therapeutic classes of drugs received and on the health status of elderly HMO members.

OBJECTIVE To assess the impact of increased prescription drug copayments on the therapeutic classes of drugs received and health status of the elderly. HYPOTHESES TESTED: Increased prescription drug copayments will reduce the relative exposure to, annual days use of, and prescription drug costs for drugs used in self-limiting conditions, but will not affect drugs used in progressive chronic conditions and will not reduce health status. STUDY DESIGN Each year over a three-year period, one or the other of two well-insured Medicare risk groups in an HMO setting had their copayments per dispensing increased. Sample sizes ranged from 6,704 to 7,962. DATA SOURCES/DATA COLLECTION Automated administrative data systems of the HMO were used to determine HMO eligibility, prescription drug utilization, and health status. ANALYSIS DESIGN: Analysis of variance or covariance was employed to measure change in dependent variables. FINDINGS Relative exposure, annual days of use, and prescription drug costs for drugs used in self-limiting conditions and in progressive chronic conditions were not affected in a consistent manner across years by increases in prescription drug copayment. Health status may have been adversely affected. Larger increases in copayments appeared to generate more changes. CONCLUSIONS Small changes in copayments did not appear to substantially affect outcomes. Large changes in copayments need further examination.