OBJECTIVES: Identify and compare demographic and clinical characteristics of patients diagnosed with osteoarthritis (OA) or chronic lower back pain (CLBP) who initiated treatment on duloxetine after FDA approval of its use for management of chronic musculoskeletal pain late in 2010. METHODS:  Commercial patients 18-64 years of age who initiated duloxetine treatment between  January 1, 2011 and July 30, 2011 were identified in the IMS Longitudinal Prescription and Medical Claims Database.  The index event was defined as the first duloxetine prescription fill with no duloxetine pill-coverage for 90 days prior. Patients were assigned to disease-category cohorts on the basis of ICD-9 codes on medical claims dated within -180/+7 days of the index event.  χ2-tests were used to compare differences across study cohorts. Additional cohorts based on other FDA approved duloxetine indications and for the same time period a year prior to the primary study period were constructed for comparison.      RESULTS: A total of 422,911 duloxetine initiators with >1 of duloxetine’s six approved indications were identified in the IMS database, of which 80,637 had either CLBP (42,280) or OA (38,357) as the only diagnosed condition from among the six.   OA patients were older than CLBP patients (60.6 vs. 52.1 years; p<0.001). An almost equal proportion of OA and CLBP patients (47%) were treated by primary care physicians.  CLBP patients were more likely prescribed an anticonvulsant (52.7% vs 37.3%; p<0.001) or an opioid (93.5% vs. 84.1%; p<.001) than were OA patients. OA patients were more likely to have been previously diagnosed with a non-CLBP related musculoskeletal pain condition. OA patients were more likely to initiate duloxetine treatment at sub-therapeutic (<40 mg/day) dosing levels than CLBP patients (32.1% vs. 26.8%; p<0.001).  Results for 2011 were little changed from 2010 results. CONCLUSIONS: Overall, patient profiles among duloxetine initiators with CLBP displayed modest differentiation relative to patients with OA in 2011.