OBJECTIVES: Multiple pharmacologic therapies have been recommended for managing fibromyalgia. However, the factors associated with each treatment initiation have not been well established. This study assessed demographic and clinical predictors of duloxetine versus other pain medications dispensed among patients with fibromyalgia. METHODS: Employing a retrospective cohort design and data from commercial insurance, this study examined predictors of treatment among fibromyalgia patients who were 18 to 64 years old and initiated duloxetine versus selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), venlafaxine, gabapentin, pregabalin, tramadol or non-tramadol narcotics between January 1, 2007 and December 31, 2008. Treatment initiation was defined as no access to the same medication over the previous 90 days, and the most recent initiation date was set as the index date. All patients selected had at least 1 fibromyalgia diagnosis (ICD-9-CM: 729.1) in the 12 months prior to initiation of each study therapy. Multiple logistic regression models were estimated to assess predictors of initiating duloxetine versus each of the other fibromyalgia therapies. RESULTS: Commercially insured fibromyalgia patients (n=117,305) were on average 48 years of age, and 76% were females. Common fibromyalgia-related comorbidities were low back pain (35%), osteoarthritis (17%), and diabetes (12%). After controlling for demographic and clinical characteristics, those 35+ years of age, females, and patients who received SSRIs, TCAs, venlafaxine, gabapentin, or pregabalin over the 1-year pre-index period were generally more likely to initiate duloxetine than the other study medications. Other predictors of duloxetine initiation included higher prescription copayment and history of rheumatoid arthritis, osteoporosis, and sleep disturbance. CONCLUSIONS: These findings indicate that age, cost sharing, presence of selected comorbidities, and prior use of certain medications to treat pain were significant predictors of duloxetine initiation among working age, commercially insured fibromyalgia patients.