OBJECTIVES: Pharmacology is considered as the main basis of medical science and so the Pharmacotherapy is a valuable therapeutic tool, however adverse drug events (ADE) are harmful just it may increase the morbidity and mortality, so the importance of surveillance in all this therapy process. The present study performed by the HHRM aims to point out what are the most common faults that can lead to ADE and plan improvements to provide greater security and quality in pharmacotherapy process.  METHODS:  Active searches from May to August of 2011 by HHRM, a multidisciplinary team, in the  pharmacotherapeutic process routinely applied in the ICU and in two clinical and one surgical wards of a public metropolitan teaching hospital with about 300 beds, by checking dosages, routes of administration, correct medical orders, correct patients, correct devices and possible drug interactions. RESULTS: There were about 5 big events of pharmacotherapy risks in a week, with non-compliance in the medical prescriptions of medicine by not recommended route (15%), wrong solutions for drugs administrations (25%), using wrong medical devices for drugs administration (10%) and electrolyte abnormalities caused by drugs (50%). There was one administration of wrong drugs in patients. The method of copy and paste in the medical prescription is a dangerous process and deserves a big attention   CONCLUSIONS: Pharmacotherapy process is very complex which errors should occurs at various stages, in any different manners and situations, so it needs the support and involvement of every health care professional and their training in order to ensure greater security and quality in healthcare, specially in pharmacotherapy knowledges. So avoiding ADE may reduce the time of hospitalization, the cost of treatment, the morbidity and even mortality. Active searches by HHRM and acting in preventing ADE risks or even correcting the possible risks is paramount for every health care service.