The objective was to determine the rate of potential drug-drug interactions in prescriptions for elderly diagnosed with Acute Coronary Syndrome in a teaching hospital. This is an exploratory, descriptive study that analyzed 607 prescriptions through databases to identify and classify the interactions based on intensity (major, moderate or minor), the mechanism (pharmacokinetic or pharmacodynamics) and documentation relevance. We detected 10,162 drug-drug interactions, distributed in 554 types of different combinations within the prescribed drugs, and 99% of prescriptions presented at least one and a maximum of 53 interactions; highlighting the prevalence of major and moderates ones. There was a correlation between the number of drug-drug interactions and the number of prescribed drugs and the hospitalization time. This study contributes for the delimitation of a prevalence pattern in drug-drug interactions in prescriptions for Acute Coronary Syndrome, besides subsidizing the importance of the effective implementation of the Clinical Pharmacy in teaching hospitals.