The study is a United Kingdom (UK) based multi-centre study which will evaluate the impact of a medication optimisation intervention (delivered in GP practices by pharmacists to patients at risk of medication related problems), on healthcare resource utilisation and patient outcomes. Pharmacists in 4 areas across the UK (3 in England and 1 in Northern Ireland) will engage with patients, thought to be at a higher risk of medication related problems, within their GP practice in order to help identify areas for improvement

Drug therapy is growing more complex as patients increasingly suffer from a number of co-morbidities. Accordingly, in clinical medicine, a wide range of medication related problems may arise (1). A medication related problem (MRP) is defined as "an event or circumstance involving drug therapy that actually or potentially interferes with desired health outcomes" (2). These problems have been found to lead to more hospital admissions and thus increase the cost of healthcare provision (3, 4). For instance, Winterstein et al. carried out a meta-analysis of research in this area which showed that 7.1% of hospital admissions were attributable to a drug related problem, of which 59% appeared avoidable (5). Moreover, a large study in the United Kingdom showed that these admissions cost the National Health Service (NHS) up to £466 million annually, which is 0.59% of the British health care budget (6).

Medication related problems (MRPs) remain a serious concern particularly in primary care settings. A recent UK study found that one in 20 prescription items in general practice included an error, affecting 1 in 8 patients. Although the majority of these errors were described as being either mild or moderate in severity, 1 in 550 of all prescription items contained an error determined to be severe (7). In addition, significant medication wastage has been found within general practice settings in England with an estimated £300 million worth of prescribed medications being wasted each year in primary and community care (8). Optimisation of drug therapy and prevention of MRPs can reduce health care expenditure, potentially save lives and enhance patient quality of life (9-13).

Medicines optimisation is defined as 'a person-centred approach to safe and effective medicines use, to ensure people obtain the best possible outcomes from their medicines. Medicines optimisation applies to people who may or may not take their medicines effectively. Shared decision-making is an essential part of evidence-based medicine, seeking to use the best available evidence to guide decisions about the care of the individual patient, taking into account their needs, preferences and values' (14, 15, 16).

Medicines optimisation requires more patient engagement and professional collaboration within health and social care settings. It focuses on actions taken by all health and social care practitioners. To support the medicines optimisation agenda a guide on medicines optimisation has been produced by The Royal Pharmaceutical Society (RPS) the aim of which is to help patients make the most of their medicines (17). This guide involves four key principles for medicines optimisation in order to achieve improved patient outcomes (16). These principles are as follows:

(i) Aim to understand the patient's experience (ii) Evidence based choice of medicines (iii) Ensure medicines use is as safe as possible (iv) Make medicines optimisation part of routine practice

In order to support the implementation of the guiding principles, NHS England launched the prototype medicines optimisation dashboard in 2014. The dashboard aims to 'encourage Clinical Commissioning Groups (CCGs) and healthcare Trusts to think more about how well their patients are supported to use medicines and less about focusing on cost and volume of drugs' (16).

Primary care systems have started utilising a team based approach to care delivery. Pharmacists have been increasingly recognised as a part of the healthcare professional team within primary care settings in many countries (18). This integration of pharmacists into primary health care systems was found to have significant benefits that included reduction of errors, effective identification and resolution of medication related problems, improvements in medication adherence, improved patient outcomes, relief of work pressure on GPs, improved communication and cooperation between health professionals, and strengthened team working within primary care (18-22).

Despite the expansion of the role of pharmacists in the primary health care setting, limited research has been conducted to evaluate the impact of pharmacist input on health service utilisation and cost.

Inclusion Criteria:

Patients are included in the study if they have any of the following:

• Have had at least 1 unplanned hospital admission or 2 or more accident and emergency department (A&E) attendances in the previous 12 months.
• Prescribed ≥ 6 regular oral/systemic, long term medicines.
• Has ≥ 2 long-term chronic conditions.

Exclusion Criteria:

• Patient is residing in a nursing home or a care home.
• Patient is considered unable to give written informed consent e.g. Alzheimer's disease.
• Palliative care patients.
• Patient has had ≥ 4 unplanned admissions to hospital in the previous 6 months.
• Patient is participating in another intervention research project within the practice.

Final results will be disseminated through relevant academic press