Effect of drug cost-sharing change on nonadherence to essential medications for acute coronary syndrome: a population based natural experiment

Abstract

Objectives: In July 2012, the Spanish drug cost-sharing scheme was reformed, providing the opportunity to evaluate the consequences of this change on patient adherence.The aim of this study was to assess the impact of the cost-sharing change on medication non- adherence in patients with acute coronary syndrome (ACS) in the Spanish region of Valencia. Methods: Population-based retrospective cohort of all patients 35 years old and over discharged after an ACS from public hospitals in the Valencia region during 2009-2011, followed until 2013.We used Difference in Difference to estimate the policy change effect on non-adherence to antiplatelet, beta-blockers, ACEI/ARB and statins of a control group –low income working popula-tion who did not change their status (40% coinsurance, unchanged)- and two inter-vention groups: pensioners (who moved from full coverage to 10% coinsurance) and middle to high income working population, for whom coinsurance grew from 40% to 50% or 60% of drug cost. Results: No significant differences in non-adherence between intervention and control groups were found for medications with low price and low patient maximum coinsurance, such as antiplatelet and beta-blockers. For ACEI/ARB and statins, the policy change had an immediate effect in the propor-tion of non-adherence in the pensioner group as compared with the control group (6.8% and 8.3% increase respectively, p<0.01 for both). Non-adherence to statins significantly increased after the reform for the middle to high income group vs. control group (7.8% increase,p<0.01).However, those effects were transitory (p<0.01 for all medications). Conclusions: Coinsurance changes may lead to increased non-adherence to proven, effective therapies, especially for higher priced agents with higher patient cost share.Adherence was already sub-optimal before the cost-sharing policy change, with a clear cost/income gradient. Consideration should be given to fully exempt high risk patients from drug cost-sharing.