Medication adherence to first-line antihypertensive drug class in a large Chinese population

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.

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%.

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.

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.