The incidence of adverse effects in hospitals is very high and a lot of them are related to medication. The most important factor in pharmaceutical interventions to reduce adverse effects is medication reconciliation, and this process is indispensable during hospital care. Reasons for reconciliation errors are numerous but high-rotation care unit, such as emergency department and short stay units (SSUs) are more hazardous areas for patient safety. Prospective observational study was performed for 3 months. Medication reconciliation and pharmacotherapeutic interventions were carried out. Indicators regarding coverage of the program, quality of prescription, and reconciliation were established and a financial analysis was done. A total of 843 patients were studied and pharmacotherapeutic intervention was carried out in 310 patients. A total of 2463 drugs were checked and 452 pharmacotherapeutic interventions were carried out. The most of these interventions belong to cardiovascular system. A total of 149 interventions were according to the pharmacotherapeutical hospital formulary and 303 were drug-related problems (DRPs). The most frequent cause of DRP was drug omission, followed by incomplete prescriptions. Of the DRP, 56.8% were reconciliation errors. The most common recommendation was starting treatment. An overall saving of $49,846.31 is estimated in this study according to the risk of an increased stay for DRP and the cost of avoidable stays. Patient's safety was increased by pharmacist's involvement on emergency department and SSUs. In SSUs, there are many polymedicated patients, so this is the most suitable place to involve the pharmacist. Pharmacist's interventions are equally accepted in both services.