OBJECTIVES: To examine the most common reasons for inpatient admissions among fibromyalgia patients who initiated duloxetine or pregabalin. METHODS: Using a large US national commercial healthcare claims database, fibromyalgia patients aged 18-64 who initiated duloxetine or pregabalin in 2006 were identified. All patients included had 12-month continuous enrollment before and after the initiation, and at least 31 total duloxetine or pregabalin supply days over the 12-month post-index period. Propensity scoring was applied to construct duloxetine and pregabalin cohorts with similar demographics, pre-index clinical and economic characteristics, and pre-index treatment patterns. Reasons for inpatient admissions between the cohorts were examined. Logistic regressions were used to assess the contribution of duloxetine versus pregabalin initiation to the top reasons for inpatient admissions controlling for cross-cohort differences. RESULTS: Per our study design, duloxetine (n=3,711) and pregabalin (n=4,111) patients had similar demographics with a mean age of 51 years and 83% females. Both cohorts had similar co-morbidities, with cardiovascular disease being the most common. Duloxetine and pregabalin patients, by the study design, also had similar total health care costs over the 12-month pre-index period ($18,970 vs. $19,019, p=0.994) with 22% contributed by inpatient care. Eight of the top 10 reasons for inpatient admissions over the 12-months post-index period were the same for both groups with intervertebral disc disorder, osteoarthritis of lower leg, and chest pain being the top 3 leading reasons. Controlling for cross-cohort differences, duloxetine patients were at a significantly lower risk for hospitalizations due to intervertebral disc disorder or major depression disorder (MDD) (odds ratios=0.44, 0.81, respectively; both p<0.0001). CONCLUSIONS: Among similar commercially-insured fibromyalgia patients who initiated duloxetine or pregabalin, the leading reasons for inpatient admissions were somewhat different between groups. Compared to pregabalin initiators, duloxetine initiators tended to be less likely to have inpatient admissions due to intervertebral disc disorder or MDD.