How payment scheme affects patients' adherence to medications? A systematic review

Background: A previous systematic review reported that increase in patients' medication cost-sharing reduced patients' adherence to medication. However, a study among patients with medication subsidies who received medication at no cost found that medication nonadherence was also high. To our knowledge, no study has evaluated the influence of different medication payment schemes on patients' medication adherence. Objective: This study aims to review research reporting the influence of payment schemes and their association with patients' medication adherence behavior. Methods: This study was conducted using systematic review of published articles. Relevant published articles were located through three electronic databases Medline, ProQuest Medical Library, and Science Direct since inception to February 2015. Included articles were then reviewed and summarized narratively. Results: Of the total of 2,683 articles located, 21 were included in the final analysis. There were four types of medication payment schemes reported in the included studies: 1) out-of-pocket expenditure or copayments; 2) drug coverage or insurance benefit; 3) prescription cap; and 4) medication subsidies. Our review found that patients with "lower self-paying constraint" were more likely to adhere to their medication (adherence rate ranged between 28.5% and 94.3%). Surprisingly, the adherence rate among patients who received medication as fully subsidized was similar (rate between 34% and 84.6%) as that of other payment schemes. The studies that evaluated patients with fully subsidized payment scheme found that the medication adherence was poor among patients with nonsevere illness. Conclusion: Although medication adherence was improved with the reduction of cost-sharing such as lower copayment, higher drug coverage, and prescription cap, patients with full-medication subsidies payment scheme (received medication at no cost) were also found to have poor adherence to their medication. Future studies comparing factors that may influence patients' adherence to medication among patients who received medication subsidies should be done to develop strategies to overcome medication nonadherence.