Simultaneous multiple prescription drugs increases the possibility of drug interactions, situation particularly critical in a hospital. The objective of the present work was to identify interactions by evaluating the originals of prescriptions archived from ward clinical of a hospital specializing in cardiology in the city of Campina Grande/PB, Brazil. The study had transversal, retrospective, and observational character with quantitative approach, and was held in the period from June to July 2010. A total of 196 prescriptions were analyzed and of these, 89.6 % had some type of interaction, and 28.0 % of prescriptions had at least one interaction. The most frequent involved were deslanosideo and furosemide (15.1 %), being classified as moderate. This study showed the importance of the pharmacist in the analysis of requirements, who may exercise the clinical pharmacy and contribute to the continuos education on medicines.