Comparison of therapy persistence for fixed versus free combination antihypertensives: a retrospective cohort study

OBJECTIVES: The aim of the study was to compare therapy persistence among patients who started with one of three drug regimens: a monotherapy, or combination therapy either as a fixed combination (ie, ‘single pill’) or as a free combination (ie, two separate antihypertensive agents). DESIGN: In a secondary data analysis, we used descriptive statistics and multivariate logistic regression to measure the effect of the three therapy regimens on therapy persistence over 4 years. SETTING: Prescription data from a large German statutory health insurance provider. PARTICIPANTS: All patients who started with a new antihypertensive therapy in 2007 or 2008 (n=8032) were included and followed for 4 years. PRIMARY OUTCOME MEASURE: Therapy persistence, defined as receiving a refill prescription no later than within 180 days. RESULTS: The persistence rates after 4 years were nearly identical among patients who started with a monotherapy (40.3%) or a fixed combination of two drugs (39.8%). However, significantly more patients who started with free-drug combinations remained therapy persistent (56.4%), resulting in an OR of 2.00 (95% CI 1.6 to 2.5; p<0.0001) for free combinations versus fixed combinations. This trend was observed in all age groups and for men and women. At the end of the study period, the number of different antihypertensive agents was still similar between patients who started with a fixed combination (2.41) and patients who started with a free combination (2.28). CONCLUSIONS: While single-pill combinations make it easier to take different drugs at once, the risk is high that these several substances are stopped at once. Therapy persistence was significantly better for patients who started with a free-drug combination without taking much fewer different antihypertensive drugs as those with a fixed combination.