Background: Bone metastases (mets) occur in ≥90% of men with castrate-resistant prostate cancer (PC), causing significant pain and resource use. Opioids are frequently used in managing pain throughout the course of care, but few studies have quantified the incremental use of opioids after the onset of bone mets. This study describes treatment patterns and incremental use of opioids among PC patients diagnosed with bone mets. Methods: Prostate cancer patients (ICD9=185.xx or 233.4) newly diagnosed with bone mets (ICD9=198.5) from 2006-2012 were identified from MarketScan databases. Patients were required to be ≥40 years, continuously eligible for medical and pharmacy benefits ≥12 months pre and ≥6 months postdiagnosis, and without evidence of other primary cancers during the study period. Patients were initially categorized as non-users of opioids (<10 days use), short-term users (≥10 but <60 days use), or long-term users (≥60 days use), and further by presence of skeletal-related events (SREs). Type of opioid therapy, proportion of time on opioids, morphine equivalent dose, and NSAID use were evaluated pre and postdiagnosis. Results: There were 4,476 patients identified for inclusion; 438 (9.8%) had an SRE. Mean age was 72 and 1.6% had chronic pain at baseline. The proportion of opioid users increased from 25.2% at baseline to 32.9% after diagnosis (P<0.0001). Among opioid users, the proportion of long-term users increased from 29.9% to 45.5% (P<0.0001). Use of monotherapy short-acting opioids decreased (pre 79.0% vs post 71.9%; P<0.0001), with a corresponding increase in mixed-action opioids (pre 13.3% vs post 23.4%; P<0.0001). Mean morphine equivalent dose (pre 7.1mg vs post 9.9mg; P<0.0001) and proportion of time on opioid therapy also increased substantially (pre 28.3% vs post 54.7%; P<0.0001). NSAID use decreased after bone met onset (pre 21.9% vs post 15.5%; P<0.0001). Opioid use and radiation therapy were more evident in patients with SREs (opioids 21.9%, opioids + radiation 32.6%, radiation 29.5%), and mean morphine equivalent dose was 10.8mg. Conclusions: Long-term opioid use and dose significantly increased after bone met onset in PC. Novel strategies that mitigate bone pain and minimize opioid use should be evaluated in this population.