OBJECTIVES: To compare dosing profiles between duloxetine and pregabalin among patients with fibromyalgia. METHODS: A retrospective cohort study was conducted on a large U.S. administrative claims database to examine commercially insured individuals aged 18 to 64 who had fibromyalgia and initiated (a 90-day clean period before initiation) duloxetine or pregabalin in 2007. Continuous enrollment in the 12 months pre- and post-index periods and at least 30-day supply of duloxetine or pregabalin over the 1-year follow-up were required for all selected patients. Average daily doses of all duloxetine or pregabalin prescriptions per person, average daily dose and average daily costs in each of the first 12 prescriptions, percent of patients with increased or decreased dose, and percent of daily dose change from previous prescription were compared between duloxetine and pregabalin cohorts. RESULTS: Both the duloxetine (n=1699) and pregabalin (n=2560) cohorts had a mean age of 51~52 years. Duloxetine-treated patients had an average initial daily dose of 55.6mg versus 159.8mg for the pregabalin-treated patients. The average daily dose per patient was 55.7mg for duloxetine and 195.4mg for pregabalin. The average duloxetine daily doses and daily costs ranged from 55.0mg-60.2mg and $3.9-$5.0 for the first 12 prescriptions and 159.8mg-265.7mg and $4.4-$5.0 for pregabalin. The percentages of daily-dose changes from previous prescription were -5.4%~3.0% for duloxetine and -1.0%~16.6% for pregabalin. Over the 1-year follow-up, both the percentages of patients with a dose increase (17.3% for duloxetine vs. 51.8% for pregabalin, p<0.01) and a dose decrease (24.8% for duloxetine vs. 10.0% for pregabalin p<0.01) were statistically different between cohorts. CONCLUSIONS: Among patients with fibromyalgia, duloxetine and pregabalin initiators had very different dosing profiles. The average daily dose for duloxetine was relatively stable over time, while pregabalin-treated patients had significant dose escalation over the 12-month follow-up period.