IMProving Adherence using Combination Therapy (IMPACT): design and protocol of a randomised controlled trial in primary care

Abstract

Background: Cardiovascular disease (CVD) is the leading cause of death, and principal reason for the large difference in life expectancy between indigenous Māori and the non-indigenous population in New Zealand. CVD guidelines recommend that people who are at high risk or who have had previous CVD should be offered aspirin, blood pressure lowering and lipid lowering therapies. However, prescribing and adherence rates are low and CVD events remain high.

Aim: To assess whether a medication strategy using a fixed dose combination pill ('polypill') could improve prescribing and adherence to recommended medications, lower blood pressure and improve lipids compared with current care over 12 months.

Methods: IMProving Adherence using Combination Therapy (IMPACT) is an open-label randomised controlled trial comparing a once-daily polypill containing four preventive medications with usual care. Six hundred participants who have had previous CVD events or are at high risk of CVD will be enrolled, including 300 Māori. Participants are identified, enrolled and prescribed either the polypill or current medications at their usual primary health care practice, with medications (including the polypill) dispensed through local community pharmacies. The polypill contains 75 mg aspirin, 40 mg simvastatin, 10mg lisinopril and either 12.5mg hydrochlorothiazide or 50mg atenolol. Primary outcomes are adherence to guidelines-recommended medications and changes in systolic blood pressure and low density lipoprotein at 12 months. Secondary outcomes include other lipids, medication dispensing, barriers to adherence, CVD and other serious adverse events, quality of life and prescriber acceptability. The trial is registered with the Australian New Zealand Clinical Trial Registry (ACTRN12606000067572).