We report a case of an elderly patient with metastatic castration-resistant prostate cancer, initially treated with abiraterone acetate (1,000 mg/day) combined with LH-RH antagonist, prednisone (10 mg/day), and zoledronic acid to manage bone metastases. In consideration of his poor performance status, radiological and biochemical progression of the disease, we decided to switch abiraterone to enzalutamide (160 mg/day). Due to adverse events, we reduced enzalutamide to a dose of 80 mg/day. Currently, the disease is under control despite the use of a low dose of enzalutamide.