Adherence to oral antihypertensive medications, are all medications equal?

Good medication adherence is a key factor in chronic disease management. Poor adherence is associated with adverse outcomes and high costs. We aimed to explore adherence rates among oral antihypertensive medications. The study included members of the Central District of Clalit Health Services in Israel aged between 40 and 75 years, who were diagnosed with hypertension before 2012 and who filled at least one prescription per year during 2012-2014, for the following medications: hydrochlorothiazide, nifedipine, amlodipine, lercanidipine hydrochloride, atenolol, bisoprolol, angiotensin-converting enzyme inhibitors (ACEI), angiotensin II receptor antagonists (ARBs), and statins. Purchase of at least nine monthly prescriptions during 2013 was considered as "good medication adherence." We compared systolic blood pressure and LDL levels, according to medication adherence, for each medication and cross-adherence rates between medications. The study included 31 530 subjects. The rates of good medication adherence varied widely among the medications investigated, ranging from 53% for statins and hydrochlorothiazide to 71% for amlodipine. Mean systolic BP and LDL levels were statistically significantly lower among persons with good, compared to lower adherence, for each of the medications investigated. Both advanced age and more chronic medications were associated with higher adherence rates for all medications tested. Poor adherence to any single medication was found to be associated with lower adherence to other medications. Different antihypertensive medications have different adherence rates. Since adherence to one medication is related to adherence to other medications, investing in medication adherence may be highly beneficial.