Drug drug interaction is defined as

Drug–drug interaction is defined as a pharmacological or clinical response to the administration of two or more drugs that is different from the response they initiate when individually administered (David and Tatro, 2012). The knowledge of the pharmacological characteristics of the drug interactions assists in their clinical management. The access to databases with detailed information on the pDDIs involved risks, their mechanism of action and management orientation largely collaborate with the prevention of adverse events (Blix et al., 2008; Duan et al., 2011; Papadopoulos and Smithburger, 2010).
Currently there are many evidences about the existence of an important relationship between the adverse events and the presence of drug interactions. A study developed by Plaza et al. (2010) in Chile pointed out in its results that 23% of clinically significant adverse events observed in the studied ICU during the research were related to drug interactions.
It was also demonstrated the need for continuous education actions linked to the presence of interactions and the use of computerized systems for their detection, which can result in satisfactory diminishing of prescription orders with potential interactions (Paterno et al., 2009; Smithburger et al., 2011; Wright et al., 2012).
Here is accentuated the necessary collaboration among the interactions alert systems and their critical evaluation by the intensivist team. The achievement of ideal results concerning the prevention of interactions combines alert systems with the pharmacist’s professional evaluation, avoiding the exposure of the clinical team to the “alert fatigue”, buy EAI045 that represents the great number of interactions signaled by the systems while not all being clinically relevant. Even though the whole clinical decision is individualized and requires a judicious evaluation on a case by case basis, it is evident the need for the critical evaluation of the clinical relevancy of the prevalent pDDIs in ICU outlining their risk profile and collecting information about their management and frequency in ICU prescription orders (Smithburger et al., 2010a,b, 2011, 2012).

Materials and methods
The study group is composed of patients admitted to the studied ICU during the data collection period. This is a general ICU, tending for potentially critical patients or patients with an unbalance of one or more organic systems due to high-complexity surgeries, grave infections and other clinical situations that demand intensive life support. The inclusion criteria were admission in ICU for more than 24h, be 18 or older and have valid prescription orders with 2 or more drugs.

Results
From January to December of 2011 were analyzed prescription orders of 369 patients (1 prescription per patient), mean age of 57.03±14.62, admitted for at least 24h in the adult Intensive Care Unit of HC – UNICAMP (average of hospitalization in adult ICU=13.34±16.49days). The study group (205 men and 164 women) represents approximately 37% of the population admitted in the ICU during this period, which has 24 beds and receives about a thousand patients per year. In the assessed period 205 different types of drugs were prescribed, (13.04±4.26 per prescription order). Table 1 shows the distribution of the drugs observed in this study according to the Anatomical Therapeutic Chemical (ATC) Classification.
During the study there were 1844 pDDIs identified, quantified, classified and distributed in 405 combinations among the prescribed drugs. In the analyzed prescription 89% presented at least one pDDI, the emphasis being on the prevalence of moderate and important interactions, present in 74% and 67% of prescription orders, respectively. Table 2 shows interactions distribution by ATC classification, their total frequency in prescription orders and the frequency of the considered clinically relevant interactions.
It was observed a number of potential interactions classified as contraindicated representing 7% of pDDIs found in the analyzed prescription orders. Metoclopramide is the drug most involved in this severity class of pDDIs, being present in 6 out of 12 listed types. By analyzing the risks associated with the observed pDDIs it was possible to determine the frequency for each physiological system, as presented by Table 3.