Introduction: Beliefs about medicines is one of the strongest determinants of adherence. It’s plausible that adherence interventions can be effective by changing patients’ beliefs about medicines.

Aim: To describe how a pharmaceutical care intervention affected beliefs about medicines and adherence.

Methods: In the Motivational Interviewing and Medication review in Coronary heart disease (MIMeRiC) trial, 316 patients were randomized to a pharmaceutical care intervention during around 6 months, or standard care. Key secondary outcome was a combination of persistence (at least one refill in the period 12–16 months) and a self-report instrument at 15 months. Beliefs about medicines specific (BMQ-S) was used as a process measure.

Results: At follow up, 88% and 77% (P = 0.033) of patients were adherent in the intervention and control group respectively. Patients who had received the intervention had a more positive necessity–concern differential (NCD) than patients with standard care, 7.9 (5.7) vs. 6.3 (5.8); P = 0.022. Patients in the intervention group who were adherent had a mean NCD of 8.8 (5.6), while intervention patients who were not adherent had mean NCD 5.4 (5.5); P = 0.046. In patients receiving standard care, the mean NCD was 6.7 (5.5) and 6.3 (5.9); P = 0.746 among patients who were adherent and not adherent at follow-up.

Conclusion: The intervention seemed to increase adherence through an effect on patients’ medication beliefs.