OBJECTIVES: The prescription of fixed-dose combinations (FDC) of antihypertensive drugs has increased rapidly since the relaxation of the prescription-term restriction. In this study, we used the opportunity of this policy change in Japan to examine the economic benefits of switching to FDC. METHODS: Claims data from 64 community pharmacies located in Tokyo were used to identify hypertensive patients under continuous treatment with angiotensin-receptor blockers (ARBs). Patients switching to FDC between December 2010 and April 2011 were compared to patients who did not receive FDC (control group). Changes in annual total and antihypertensive drug costs were compared for both groups, using a difference-in-differences approach to adjust for patient characteristics and use of concomitant medication. RESULTS: There were 542 patients who switched to FDC and 9664 patients in the control group. No significant differences were observed between the 2 groups, except for antihypertensive drug use patterns before the policy change. The switch to FDC was associated with annual savings of 6151 yen (US$87.70) in total drug costs and 10,420 yen (US$124.20) in antihypertensive drug costs. Approximately 20% of the FDC patients, however, switched from ARB alone and their treatment costs increased by 3795 yen (US$37.10). CONCLUSIONS: For hypertensive patients who required ARB-based combination therapy, switching to FDC drugs had a significant cost-saving effect. However, the policy change of relaxing the prescription-term restriction could encourage aggressive treatment, i.e., switching to a combination therapy from monotherapy, regardless of medical conditions. Further research is required to evaluate the possible negative aspects of FDC drugs.