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.

Methods A series of semistructured, in-depth interviews with local health professionals and UMPIRE trial participants in India and the UK will be undertaken. The aim is to understand their views and experiences of the trial context and of day-to-day use of medications more generally. The grounded theory approach will be used to analyse data and help inform the processes of the UMPIRE trial.

Ethics and dissemination The study has received ethical approval for all sites in the UK and India where trial participant interviews will be undertaken. The process evaluation will help inform and enhance the understanding of the UMPIRE trial results and its applicability to clinical practice as well as shaping policy regarding strategies for improving cardiovascular medication adherence.