Abstract
PURPOSE: Suboptimal adherence to antihypertensive agents leads to adverse clinical outcomes. This study aims to evaluate the association between first-line antihypertensive drug class and medication adherence in a large Chinese population. METHODS: All patients prescribed ≥ one antihypertensive drug in 2001-2003 and 2005 who have paid at least two consecutive clinic visits in the public healthcare system of Hong Kong were included. We excluded patients who have followed-up in the clinics for ≤ 30 days. Interval-based Proportion of Days Covered (PDC) was used to assess medication adherence. All patients were followed-up for up to 5 years. Binary logistic regression analysis was used to evaluate the factors associated with optimal adherence, defined as PDC ≥ 80%. RESULTS: From 147,914 eligible patients, 69.2% were adherent to the antihypertensive prescriptions. When compared with angiotensin converting enzyme inhibitors (ACEIs), patients initially prescribed α-blockers (adjusted odds ratio [AOR]=0.234, 95% C.I. 0.215-0.256), β-blockers (AOR=0.447, 95% C.I. 0.420, 0.477), thiazide diuretics (AOR=0.431 95% C.I. 0.399, 0.466) and calcium channel blockers (AOR=0.451, 95% C.I. 0.423, 0.481) were significantly less likely to be drug adherers. Angiotensin receptor blockers (ARBs) and fixed-dose combination therapies were similarly likely to be medication adherent. Older age, male gender, visits in general out-patient clinics, residence in urbanized regions, and the presence of comorbidity were positively associated with optimal drug adherence. CONCLUSION: Patients receiving initial prescriptions of ACEIs, ARB and combination therapy had more favorable adherence profiles than the other major antihypertensive classes in real-life clinical practice.