Antihypertensive use before and after initiation of fixed-dose combination products in Australia: a retrospective study

Abstract

BACKGROUND National guidelines in Australia advise that patients should be stabilised on both individual antihypertensive medicines before initiating a fixed-dose combination (FDC) product. The aim of this study was to examine the antihypertensive medicines use before and after initiation of four antihypertensive FDC products recently listed under the Australian Pharmaceutical Benefits Scheme--olmesartan or valsartan with hydrochlorothiazide, valsartan with amlodipine and ramipril with felodipine. SETTING Australian veteran population This was a retrospective cohort study using Australian Government Department of Veterans' Affairs pharmacy claims data. Subjects initiating a FDC between 2008 and 2010 were included. Their antihypertensive medicine use was investigated in the 12-months prior to and post FDC product initiation. Proportions of FDC initiators dispensed one or both of the individual medicines, or who had antihypertensive medicines other than the individual ones were assessed for the 12 months prior to initiation. For the post history, proportions of patients who continued the FDC as a sole therapy, had other antihypertensives co-administered with FDC, or ceased the FDC were established. 2,513 participants initiated one of the four FDC products in the study period. Immediately prior to FDC initiation, below 1 % had both individual medicines, 29 % had one of the individual medicines, 58 % had antihypertensive medicines other than the individual ones, and 12 % had no antihypertensive therapy. At 12 months post initiation, 25 % of the FDC initiators continued it as a sole treatment, 35 % required an additional antihypertensive medicine in addition to FDC product, and 40 % ceased the FDC. A minority of patients initiated combination products after being stabilised on both individual medicines. Significant number had no prior history of antihypertensive use. One-third of FDC initiators still required additional antihypertensive medication concurrently with the FDC product at 12 months post initiation.