Effectiveness of a patient-centred complex intervention to improve Initial Medication Adherence to cardiovascular disease and diabetes treatments in primary care (the IMA-cRCT study): a pragmatic cluster randomised controlled trial using real-world data.

Introduction: Non-adherence to cardiovascular disease and diabetes treatments contributes to suboptimal clinical outcomes and higher cost. The initial medication adherence (IMA) intervention is a multidisciplinary primary care (PC) intervention based on shared decision-making (SDM). The IMA-cluster-randomised controlled trial (cRCT) study evaluated the impact of the IMA intervention on medication initiation, secondary adherence and clinical outcomes compared with usual care (UC).

Methods: This was a pragmatic cRCT with a hybrid effectiveness-implementation design which randomised 24 PC centres in Spain to intervention or UC. Patients receiving a new prescription of antihypertensive, lipid-lowering, antiplatelet and/or oral/injectable antidiabetic medication at the intervention centres (March 2022-September 2022) were attended by general practitioners (GPs), nurses and community pharmacists who had been trained in SDM and given decision aids (leaflets and website). Real-world data from prescription and dispensing records-used to assess medication initiation and secondary adherence (correct dosing and continued use)-and clinical outcome data from electronic health records were collected up to 18 months after initial prescription and analysed using multilevel regression models.

Results: Overall, 4910 prescriptions were issued to 3629 patients (Intervention=2148; UC=1481) by 150 GPs (Intervention=91; UC=59). No differences were detected between groups in medication initiation or secondary adherence. Among clinical outcomes, only blood pressure outcomes favoured the IMA intervention, reflecting a small but clinically meaningful improvement.

Conclusions: The IMA intervention had limited overall impact, with no effect on adherence, but showed potential benefits in blood pressure. However, SDM, as an ethically grounded approach, may enhance patients and professional experiences, supporting its consideration for broader implementation. Future efforts should prioritise these benefits by investing in professional training and patient support, addressing implementation challenges and deepening understanding of SDM effects, which would warrant further evaluation.

Trial registration number: NCT05026775.