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 copayme nts 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 prescri ption drug costs for drugs used in self-limiting conditions, but will not affect drugs used in progressive chronic conditions and will not r educe 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 s etting had their copayments per dispensing increased. Sample sizes ran ged from 6,704 to 7,962. Data Sources/Data Collection. Automated admin istrative data systems of the HMO were used to determine HMO eligibili ty, 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 consiste nt manner across years by increases in prescription drug copayment. He alth status may have been adversely affected. Larger increases in copa yments appeared to generate more changes. Conclusions. Small changes i n copayments did not appear to substantially affect outcomes. Large ch anges in copayments need further examination.