Linkage between electronic prescribing data and pharmacy claims records to determine primary adherence: the case of antihypertensive therapy in the Lisbon and Tagus Valley Region, Portugal

Abstract

Abstract Background Hypertension (HT) is highly prevalent and a major risk factor for cardiovascular disease. Over 42% of Portuguese adults have HT. Even though the benefits of antihypertensive (AHT) drugs have been demonstrated, HT control remains inadequate. One major reason is that patients often fail to take their medications as prescribed. This paper aims to determine primary adherence to AHT therapy in newly diagnosed and treated hypertensive patients in Primary Health Care (PHC) units of Lisbon and Tagus Valley Health Region. Methods This study reports data from a population-based, retrospective, cohort study from patients diagnosed with HT in PHC units of Lisbon and Tagus Valley Region from 1 January to 31 March 2011, with no prior use of AHT drugs. Primary adherence rate was expressed as number of claims records/total number of prescriptions records. Data were collected from SIARS for each patient during a 2-year period. Results Overall primary adherence rate was 58.5%, increasing with age. Rates were higher for men, living in the Lisbon Metropolitan Area and diagnosed with uncomplicated HT. Drugs acting on the renin–angiotensin system had the highest rates, increasing for fixed-dose combinations and diminishing with the increase of cost for the patient. Conclusions Overall, almost 1 out of 2 prescribed AHT drugs were not dispensed. Until this study, little was known in Portugal about primary adherence. Our findings imply that the potential benefits of AHT therapy cannot be fully realized in this population.