IMPPP is a 48-month 3-phase study adhering to the principles of the MRC framework for complex interventions.

Phase 1 (Development)
A mixed-methods study in 2 Scottish Health Boards that are implementing novel informatics tools to support NHS polypharmacy reviews. Interviews with healthcare professionals (HCPs) plus patient focus groups will be used to understand implementation and their experience of polypharmacy review, and the strengths/limitations of the various intervention components. Epidemiological analysis of practice data will be used to explore the prevalence, variation and amenability to change in potentially inappropriate prescribing (PIP). These findings will inform the initial intervention design, which will then be refined in consultation with HCP and patient groups.

Phase 2 (Optimisation)
A pilot-feasibility study in 5 West of England GP surgeries to optimise the intervention in the English context. A formative qualitative process evaluation will examine initial adoption and intervention implementation, including likely barriers/facilitators to implementation which will be addressed prior to the full trial. We will also pilot/evaluate trial processes including collecting quantitative data on patient recruitment/retention.

Phase 3 (Evaluation)
A multicentre cluster-RCT comparing intervention vs. usual care. The primary outcome is the mean number of PIP indicators triggered per patient. Secondary outcomes include quality of life, health service use and treatment burden. A cost-effectiveness analysis will be conducted. A parallel mixed-methods process evaluation will be undertaken examining implementation to help explain the success or otherwise of the intervention, and to inform subsequent implementation in practice.