Background/Purpose: Patients with fibromyalgia (FM) tend to use a number of different medications and have high health care costs. Treatment for FM generally consists of symptom management. The objective of this study was to describe clinical characteristics and health care utilization patterns in patients with FM newly prescribed amitriptyline, duloxetine, gabapentin or pregabalin.

Methods: We conducted a large population-based cohort study using US health care utilization data (1/2007-12/2009). Adult patients were categorized into four groups if they were newly prescribed amitriptyline, duloxetine, gabapentin or pregabalin after their first diagnosis of fibromyalgia (ICD-9 code 729.1). A 180-day baseline period free of any of the four drugs was required prior to the first prescription date (index date). Demographic characteristics and comorbidities during the baseline period and their relationship with use of FM-related drugs and health care utilization patterns during the follow-up period were examined.

Results: The study population included a total of 74,378 patients with FM with a mean follow-up period of 141 to 195 days. The mean ages were 48 to 51 years and 72% to 81% were women, depending on the prescribed drug. Comorbidities were similar across the four groups ranging from a mean of 0.5 to 0.8 conditions.  Back pain (48%-65%) was the most frequent comorbidity in all four groups and hypertension (29%-38%), headache (22%-30%), depression (11%-24%), sleep disorder (16%-19%) and inflammatory arthritis (10%-15%) were also common across the four groups. Median daily dose (in milligram) at both index date and the last day of follow-up was 25 for amitriptyline, 60 for duloxetine, 300 for gabapentin, and 75 for pregabalin.  The mean number of physician visits ranged from 6.6 to 9.0 and mean number of prescription drugs were from 7.9 to 9.6 during the follow-up. Table shows a slight decrease in the use of various FM-related drugs after the index date across the four groups. Opioids and antidepressants were most commonly taken with drugs for FM.  

Conclusion: Patients who were newly prescribed one of the four common drugs for FM similarly had multiple comorbidities, a great number of other medication use and high health care utilizations. Median daily dose for all four drugs remained the same during the follow-up.

Table.  Use of fibromyalgia-related drugs before and after the index date (%).