The Effects of Copayments on Medication Adherence During the First Two Years of Prescription Drug Treatment

Objective: The aim of this study was to examine effects of initial prescription copayment size and observed increase on adherence by analyzing data from a managed care database. Methods: Medical-pharmacy claims data were abstracted from the Integrated Health Care Information Services (IHCIS) National Managed Care Benchmark database for primary employer-sponsored subscribers. Incident fills and refills for the 10 most common medication groups between 2001 and 2003 were predicted by size and observed increase in copayment with the use of survival analysis. Results: High copayments and observed copayment increases were associated with termination of medication use. Whereas effects of copayment level were limited to the first few fills., effects of observed increases in copayments were persistent. Conclusions: The strategy of increasing initially low copayments after the patient has made enough fills to become insensitive to copayment level is contraindicated by observed increases in copayment, predicting termination. However, other financial incentives might nonetheless help reduce early termination of medication use.