Twelve months of uninterrupted thienopyridine therapy after drug-eluting stents (DES) implantation was recently recommended, but limited data are available regarding long-term use in clinical practice. The objective of the study was to determine the adherence to thienopyridine therapy after stent implantation, factors associated with suboptimal adherence, and association of suboptimal adherence with mortality.

We evaluated 5,263 older patients (>65 years) who received DES and 6,081 older patients who received bare-metal stents (BMS) from December 1, 2003, to March 31, 2006, in Ontario, Canada, who were eligible to receive 12 months of thienopyridine at minimal cost.

Primary nonadherence was observed among 6.9% in the DES group and 7.1% in the BMS group that did not fill a single prescription of thienopyridine within 1 year of stent implantation. Premature discontinuation occurred in a progressive manner, with 28% in the DES group and 34% in the BMS group discontinuing therapy by 6 months. Low-income patients eligible for a waiver of deductible and dispensing fee were almost 70% more likely to fill their first prescription. For DES patients, primary nonadherence (hazard ratio [HR] 2.68, 95% CI 1.77-4.07), 12-months proportional days covered <80% (HR 2.39, 95% CI 1.67-3.43), and prematurely discontinuing therapy within 6 months (HR 2.64, 95% 1.60-4.35) were associated with an increased risk of death.

We found suboptimal patterns of adherence to thienopyridine therapy after DES implantation that was strongly associated with an increased mortality risk. Eliminating any costs for thienopyridine therapy may be an effective strategy to increase medication adherence.