Antihypertensive therapy among newly treated patients: An analysis of adherence and cost of treatment over years

OBJECTIVE: To perform a time-trend analysis of adherence and cost of antihypertensive treatment over four years. METHODS: A population-based retrospective cohort study was conducted. We included subjects ≥18 years, and newly treated for hypertension with diuretics, beta-blockers, calcium channel blockers, angiotensin-converting enzyme inhibitors, or angiotensin receptor blockers between 01 January 2004 and 31 December 2007. One-year adherence to antihypertensive therapy was calculated and classified as low, low-intermediate, intermediate, high-intermediate, and high. The direct cost of antihypertensive medications was evaluated. RESULTS: We included data for a total of 105,512 patients. The number of newly treated subjects decreased from 27,334 in 2004 to 23,812 in 2007, as well as antihypertensive drug therapy cost which decreased from €2,654,166 in 2004 to €2,343,221 in 2007. On the other hand, in the same time frame, the percentage of adherent newly treated subjects increased from 22.9% to 28.0%. Compared with subjects initiated on angiotensin receptor blockers (odds ratio [OR] = 1), the risk of nonadherence was higher in those initiated on angiotensin-converting enzyme inhibitors (OR = 1.19), combination therapy (OR = 1.44), beta-blockers (OR = 1.56), calcium channel blockers (OR = 1.67), and diuretics (OR = 4.28). CONCLUSIONS: The findings of the present study indicate that suboptimal adherence to antihypertensive medication occurs in a substantial proportion of treated patients, and improvements in treatment adherence were obtained but are still unsatisfactory.