Background Medication adherence following acute coronary syndrome (ACS) is often sub-optimal and is associated with poor clinical outcomes. Patients' beliefs about medications have been shown to predict poor adherence and may be targetable for intervention. Findings novel ways to improve adherence is an important area of research with widespread clinical implications. Pharmacists may currently be underutilised in promoting and monitoring medication-taking behaviour. There have been few effective interventions led by pharmacists to support medication adherence in patients with ACS.

Objectives This study follows on from a feasibility and acceptability study recently conducted (NCT02967588). The primary objective is to pilot a pharmacist-led hospital-based intervention to support medication adherence following an ACS.

Methods This study will adopt a non-randomised intervention cohort design (i.e. controlled before-and-after (CBA) study). Patients admitted to hospital with an ACS will be recruited for this study. Patients must be prescribed medicines for secondary prevention. The study will be delivered by hospital pharmacists over two sessions and will target both intentional (Session 1) and unintentional (Session 2) adherence barriers. Session 1 will involve eliciting and challenging patients' erroneous beliefs about medications. Session 2 will involve formulating specific action plans to encourage medication-taking habit formation.

Outcome Outcome data will be collected at two time points - 6 week and 12 week follow up. The primary outcome of this proposed study will be treatment beliefs, measured using the Beliefs about Medicines Questionnaire-Specific (BMQ-S) (Horne, Weinman & Hankin, 1999). Our secondary outcome will be self-reported medication adherence measured using the Medication Adherence Report Scale (MARS-5) (Horne & Weinman, 2002). Depression, medicines-related self-efficacy and satisfaction with medicines information provision will also be measured.

Study timeline Control cohort ('before' group): eligible patients will receive treatment as usual (TAU) and will complete all outcome measures (i.e. treatment beliefs, medication adherence). Pharmacists will then be trained to deliver the intervention. Intervention cohort ('after' group): eligible patients will receive the pharmacist-led intervention and will complete all outcome measures.

Inclusion Criteria:

• Patients aged 18 years and over
• Clinical diagnosis of ACS*
• ACS primary reason for hospitalisation
• Patients to be prescribed medications for secondary prevention (i.e. antiplatelet drugs, statins, ACEi, ARBs, β-blockers)
• Sufficient spoken English to participate in the study

Exclusion Criteria:

• Under 18 years of age

• Developed ACS* as a secondary condition (i.e. perioperative MI)

• Not prescribed medications for secondary prevention (i.e. antiplatelet drugs, statins, ACEi, ARBs, β-blockers)

• Non-English speaking

• Medical notes indicate cognitive impairment

  *ACS is defined as patients diagnosed with a myocardial infarction or unstable angina (European Society of Cardiology Clinical Practice Guidelines (Roffi et al., 2015; Steg et al., 2012)).

• Non-ST-segment elevated myocardial infarction (NSTEMI) - Myocardial ischaemia with elevated cardiac biomarkers (i.e. troponin) in the absence of ST-segment elevation identified via electrocardiogram (ECG).

• ST-segment elevated myocardial infarction (STEMI) - Myocardial ischaemia with elevated cardiac biomarkers (i.e. troponin) and ST-segment elevation identified via electrocardiogram (ECG).

• Unstable angina - Myocardial ischaemia at rest or minimal exertion in the absence of cardiomyocyte necrosis and significantly elevated cardiac biomarkers (i.e. troponin).

All diagnoses will be made by the patients' clinical team. The research team will play no part in this process.