Fixed-dose combinations (FDCs) for blood pressure control can simplify prescribing, improve medication adherence, and be cost-effective. In Japan, real-world data about the class effects of antihypertensive drugs on medication adherence are limited. Using the nationwide database of medical health claims from Diagnosis Procedure Combination hospitals, treatment patterns and adherence were analyzed for 47,891 patients prescribed antihypertensive medication between April 2014 and March 2015. Adherence was assessed by the proportion of days covered (expressed as % PDC). Patients were prescribed a mean of 2.0 ± 1.0 antihypertensive drugs and 2.4 ± 1.7 pills for their index prescription. Mean adherence overall was 91.5% PDC and was inversely correlated with the number of antihypertensive drugs or pills prescribed on the index date. Mean % PDC was significantly higher (all P < 0.0001) for CCB + ARB versus ARB + thiazide diuretic combinations and for CCB + ARB + β-blocker versus CCB + ARB + thiazide diuretic combinations. Adherence was significantly higher (P < 0.0001) for FDC (CCB + ARB) versus corresponding single-drug combinations, but not for other comparisons of FDCs versus single-drug combinations. On the other hand, FDCs were not always used effectively; specifically, FDCs were frequently used concomitantly with a single agent(s) from the same drug class(es) as the FDC. From the results of our study, no clear differences were observed in medication adherence according to the presence or absence of FDC formulations, and there were cases in which FDCs were not being utilized effectively to simplify prescribing.
Keywords: Antihypertensives; Combination therapy; Fixed-dose combinations; Hypertension; Treatment adherence.