Background The chances of Adverse Drug Reactions (ADR) occurrence can be correlated to the presence of Potential Drug Interactions (PDI) in medical prescriptions, which makes PDIs one of the main concerns for a Clinical Pharmacist in the Intensive Care Unit (ICU).

Purpose The aim of this study was to evaluate the existence of Theoretical Potential Drug Interactions (TPDI) in prescriptions made at the ICU of a Public Hospital (Hospital de Clinicas-UNICAMP), and also quantify and classify them based on level of severity, thus providing a profile of the prescriptions of this sector.

Materials and methods Between the months of January to June of 2011, a total of 195 prescriptions to patients aged 18 years or older who had been hospitalised for more than 24 h in adult ICU were evaluated.

Results During the study period, 172 different types of medications were prescribed, with an average of 12.9±4.3 by prescription. Among the prescriptions evaluated, 88.2% had theoretical potential drug interactions that resulted in an average of 4.7±4.9 by prescription. The 915 TPDI observed in that prescriptions were classified as contraindicated (20), major (257), moderate (516) and minor (122), using information from the database Micromedex. These TPDI were reported to the medical team according to their severity and the need for clinical management. The pharmaceutical interventions were immediately carried out, based on the classification of severity and the patient's condition.

Conclusions This research collaborates to the delimitation of the pharmacotherapy procedures used in intensive care, demonstrating that there is a high incidence of TPDI in them, and providing immediate and future interventions based on the classification of severity for the prevention of avoidable adverse events in this sector. It also highlights the Clinical Pharmacist's contribution in this area, helping the multidisciplinary team to reduce the risks in drug therapy.