This a prospective single arm study enrolling patients with bone metastases from breast cancer who have been on opioid therapy for bone pain for at least 4 weeks. All patients start on Syndros at 4.2 mg po BID for 3 days, if tolerated without side effects the dose is increased to 8.4 mg QAM and 4.2 mg QPM for an additional 3 days. If the patient continues to tolerate the medication, the dose will be increased to 8.4 mg BID for the rest of the study period (total of 8wks). For patients who have side effects secondary to Sydnros, the dose will be decreased. Side effect assessment will be done by the research team 2 days after making the dose adjustment. If subject continues to have side effects, dose will be held until resolution of symptoms. If the study medicine is held for more than a week continuously, they will be taken off the study. In addition, they will have baseline blood and urine collected for biomarkers and also complete study related questionnaires (for secondary end points). They are also provided an opioid drug diary which they will take home during visit 1 to record their opioid pain medication use. Research staff will be calling patients on a weekly basis to reinforce opioid drug diary, assess for Syndros side effect, and adjust dose of Syndros. At the end of 8 weeks blood and urine is collected again and they will complete the study questionnaires.
