INterpreting the Processes of the UMPIRE Trial (INPUT): protocol for a qualitative process evaluation study of a fixed-dose combination (FDC) strategy to improve adherence to cardiovascular medications.

Introduction: This paper describes a planned process evaluation of the Use of a Multidrug Pill In Reducing Cardiovascular Events (UMPIRE) trial, one of several randomised clinical trials taking place globally to assess the potential of cardiovascular drugs as a fixed-dose combination (polypill) in cardiovascular disease prevention. A fixed-dose combination may be a promising strategy for promoting adherence to medication; alleviating pill burden through simplifying regimens and reducing cost. This process evaluation will complement the UMPIRE trial by using qualitative research methods to inform understanding of the complex interplay of factors that underpin trial outcomes.