categories C, D and X have been considered. The degree of rigor and the reliability rating were also collected. Results A total of 69 men were interviewed. The mean age was 77 years, all older than 60 years. 31 patients were receiving treatment with apalutamide, 26 with abiraterone and 12 with enzalutamide. The patients had a mean of 12.6 ± 15.1 months of treatment. 88.5% took 5 or more medications.A total of 709 lines of treatment were analysed, finding that 66.6% of the patients presented an interaction in their treatments, 1.9 interactions per patient.According to the severity of the interactions, 76.2% (91) were C, 10.1% (12) D and 12.7% (15) category X. 63.5% of the interactions were with apalutamide, 26.2% with enzalutamide and 10.1% with abiraterone. 4 pharmacological groups are responsible for category D interactions and 1 is responsible for category X interactions (proton pump inhibitors). Conclusion and Relevance. The study has allowed us to detect a high number of interactions, although the proportion of patients with clinically relevant interactions is low. . The pharmacist plays a very important role in the prevention, detection and monitoring of interactions in this group of patients.