Objectives To describe a clinical pharmacist’s (CP) activity in an emergency department (ED) regarding medication reconciliation and optimisation of pharmacotherapy of patients at hospital admission.

Methods A 1-year prospective observational study was conducted to analyse the activity of a CP in the ED of a 350-bed hospital in Spain. The CP reviewed home medications and medical prescriptions of patients to perform medication reconciliation if required and intervene if medication errors were detected.

Results The CP reviewed medications and medical orders of 1048 patients. 816 patients had home medication: 440 patients (53.9%) were correctly reconciled by the physician; 136 (16.7%) were reconciled by the physician with unintentional discrepancies; and 240 (29.4%) by the CP, with a higher percentage in patients admitted to surgical departments (χ²:38.698; P<0.001). Following pharmaceutical validation, 434 pharmaceutical interventions were performed.

Conclusions The presence of a CP in an ED could increase the detection of reconciliation errors and help resolve medication errors.