A retrospective, population-based analysis of persistence with antihypertensive drug therapy in primary care practice in Italy

Background: Many hypertensive patients discontinue drug therapy despite the increased cardiovascular risk associated with inadequately controlled hypertension. However, most experiments do not address this premature discontinuation of therapy, making it difficult to project the appropriateness of antihypertensive drugs in real-world use. Objective: The goal of this study was to assess patients' persistence with antihypertensive drug therapy in a nonexperimental setting. Methods: An administrative database kept by the Local Health Unit of Ravenna, Ravenna, Italy, listing patient baseline characteristics, drug prescriptions, and hospital admissions was used to perform a population-based, retrospective study. The study included all patients who met the following criteria from January I through December 31, 1997: new user of antihypertensive drugs; greater than or equal to20 years of age; receiving a first prescription for a diuretic, beta-blocker, calcium channel blocker, angiotensin II-receptor antagonist (AIIA), or angiotensin-converting enzyme inhibitor. All prescriptions for antihypertensive drugs filled during the 12-month follow-up period were used to define patients as continuers, switchers, or discontinuers on the basis of their persistence with therapy. Results: A total of 16,783 patients were included in the study analyses: 7409 men (44.1%) and 9374 women (55.9%), with an average age of 56.1 +/- 18.3 years (range, 20-105 years). Of this study population, 64.9% (n = 10,894) discontinued treatment over the course of follow-up, 26.9% (n = 4508) continued treatment with the initially prescribed medication (with 5.1% [n = 862] adding another medication for combination therapy), and 8.2% (n = 1381) switched medications. Patients initially prescribed AIIAs were more likely to continue treatment than those initiated on other types of antihypertensives (P < 0.001). Discontinuation was associated with younger age, lower prevalence of concurrent chronic pharmacotherapies, and lower prevalence of previous hospitalizations for cardiovascular disease (all P < 0.001). Conclusions: Health care claims data are a powerful tool for measuring continuation of therapy, providing detailed, population-wide epidemiologic and economic information for analyzing antihypertensive drug treatment. Further studies are required to relate pharmacotherapy to outcomes.