Discontinuation of low-dose acetylsalicylic acid therapy in UK primary care: incidence and predictors in patients with cardiovascular disease

BACKGROUND Discontinuation of low-dose acetylsalicylic acid (ASA) leads to an increased risk of cardiovascular and cerebrovascular events in patients taking low-dose ASA for secondary cardiovascular prevention. However, little is known about the rate of discontinuation in everyday clinical practice. OBJECTIVES To assess the rate of low-dose ASA discontinuation in primary care, and identify factors that predict discontinuation. METHODS The Health Improvement Network, a large UK primary care database, was used to identify patients aged 50-84 years who received at least two consecutive prescriptions for low-dose ASA for secondary cardiovascular or cerebrovascular prevention in 2000-2007 (n = 35,639). Discontinuation was defined as a period of at least 90 days after completion of the last prescribed course of ASA during which no repeat prescription was issued. RESULTS During the study, 11,729 patients (32.9%) discontinued ASA therapy (mean follow-up 2.5 years). The discontinuation rate was lower in patients with ASA indicated for myocardial infarction than for other indications. The diagnosis of gastrointestinal disorders during the study (overall odds ratio: 1.74; 95% confidence interval: 1.61-1.88) was associated with increased rates of ASA discontinuation, whereas co-prescription of a proton pump inhibitor from the start of ASA therapy was associated with a decreased rate of discontinuation (odds ratio: 0.80; 95% confidence interval: 0.75-0.86). Co-prescription of several other cardioprotective medications was also associated with a reduced risk of discontinuation, as were increasing age, prior hospitalization and overall number of co-medications. CONCLUSION Continuous co-prescription of a PPI with low-dose ASA may improve adherence and outcomes, particularly in patients at both cardiovascular and gastrointestinal risk.