The demand for statin: the effect of copay on utilization and compliance

Increasing drug costs in the US have prompted employers and insurers alike to turn to higher drug copays for cost containment. The effect of rising copays on compliance with statins (HMG-CoA reductase inhibitors) treatment has received surprisingly little attention in the applied literature. This paper uses pharmacy claims data from a commercially insured adult population to determine the effect of copay change on compliance at the individual level. Fixed effect logit and Poisson regressions estimate the effect of copays on monthly likelihood of high compliance and average monthly days of supply respectively. Higher copays reduce compliance among statin users, with less compliant patients responding more strongly to copay change than compliant patients. These results suggest that specific financial incentives given to less compliant patients could improve compliance with statin treatment at a relatively low cost.