The "Emergency Department (ED) Pharmacist" is an integrated part of the ED interdisciplinary team in many countries, which have shown to improve medication safety and reduce costs related to hospitalisations. In Norway, few EDs are equipped with an ED pharmacist, and research describing effects on patients has not been conducted.

This is a multicentre study where the intervention will be implemented in the regular operation of three EDs in Northern Norway; Tromsø, Bodø and Harstad.

Clinical pharmacists will work as an integrated part of the ED team, and provide pharmaceutical care services such as medication reconciliation, medication review or medication counselling. The medical condition and complexity of the patient's disease will influence the extend and type of service from the pharmacist.

A non-randomized stepped wedge study design will be applied, where the ED pharmacist will be implemented in all three EDs after a three, six- and nine- month control period, respectively. Each ED will consequently have both intervention and control periods.

All patients going through the three EDs during the 12-month study period will be included. Patients admitted in the control periods will be allocated to the control group, while patients admitted in the intervention periods will be allocated to the intervention group.

The primary endpoint is "Time in hospital during 30 days after admission to the ED", which is a composite endpoint combining i) time in ED during stay, ii) time in hospital during stay if hospitalized and iii) time in urgent care clinic, ED and/or hospital if rehospitalized within 30 days after admission to ED Secondary endpoints include time to rehospitalization, length of stay (LOS) during first hospitalisation, LOS in EDs, rehospitalisation rates and mortality rates.

Patient data will be collected retrospectively from national data registries, from the hospital system and from patient records.

The Regional Committee for Medical and Health Research Ethics and Local Patient Protection Officers in all hospitals have approved the study.

The intervention will be assessed using a non-randomized stepped wedge trial design. A stepped wedge design allows for the intervention to be rolled out at different times, thus allowing us to control for differences between study sites (vertical control) and secular trends (horizontal control) during the study period. This is the gold standard when a conventional randomized controlled trial is not possible.

The stepped wedge study design is based on a staggered implementation of the intervention in the intervention sites. This will be done over a 12-month period, starting with a three-month control period in all EDs (planned start-up February 1st, 2021). This period allows for baseline data collection before the intervention. After this period, the investigators will consecutively roll out the intervention at three months interval to the EDs. The intervention will start in Tromsø which is the largest ED, continue in Bodø and finish in Harstad, which is the smallest of the three EDs. After nine months, all EDs will have clinical pharmacists. When the intervention is implemented in an ED, it will continue until the trial is terminated (planned January 31th, 2022).

This is a multicentre study including three EDs in Northern Norway Health Authority region; the University Hospital of North Norway (UNN) Tromsø, Nordland Hospital (NLSH) in Bodø and UNN Harstad with approximately 15 000, 12 000 and 6000 patients presenting annually in the respective EDs. These numbers include patients being admitted more than once to the ED. The three EDs operate similarly and receive patients who need immediate health care in case of acute illness or injury. Norway has a well-functioning primary care system, including municipal urgent care clinics providing ambulatory care outside of general practitioner (GP) office hours. In order to be admitted to the ED, the patients need a referral either from GP or from a physician at an urgent care clinic. At the ED, the patient is met by an ED nurse and an ED physician (either an intern or a resident in specialty training), who perform the initial examinations and assessments of the patient. A senior physician is always on call in case of the need for a consultation. NLSH is the only ED with senior physicians situated in the ED during day-time. From the ED, patients are either admitted to a hospital ward, transferred to a municipally run health institution or discharged to their homes.

All patients presenting to the EDs during the study period will be included. Patients presenting during the control period, will be allocated to the control group (n≈14400), while patients presenting during the intervention period will be allocated to the intervention group (n≈19200), independently of whether they receive clinical pharmacist services or not. Patients for whom data is not available retrospectively, will be excluded.

Inclusion Criteria:

• All patients presenting to the EDs during the study period will be included.

Exclusion Criteria:

• Patients for whom data is not available retrospectively.
• Patients who actively ask not to be included in the study.

Masking members of the interdisciplinary team is not possible as a new member of staff is being introduced. However, the study will not be announced to patients presenting to the EDs.

Patients will know that there is a study ongoing, but will not have to consent to participation.