Clinical characteristics and medication uses among fibromyalgia patients newly prescribed amitriptyline, duloxetine, gabapentin, or pregabalin

Abstract

Objective: Fibromyalgia is a common chronic pain disorder with unclear etiology. No definitive treatment is available for fibromyalgia, and treatment with antidepressants or antiepileptics is often used for symptom management.

Methods: Using US health care utilization data, a large population-based cohort study was conducted to describe clinical characteristics and medication use patterns in patients diagnosed with fibromyalgia who newly started amitriptyline, duloxetine, gabapentin, or pregabalin.

Results: There were 13,404 amitriptyline starters, 18,420 duloxetine starters, 23,268 gabapentin starters, and 19,286 pregabalin starters. The mean age ranged from 48–51 years and 72–84% in each group were women. Back pain was the most frequent comorbidity in all 4 groups (range 48–64%) and hypertension, headache, depression, and sleep disorder were also common. The median daily dose at the start of followup was 25 mg for amitriptyline, 60 mg for duloxetine, 300 mg for gabapentin, and 75 mg for pregabalin, and >60% of patients remained on the same dose throughout the follow up period. Only one-fifth of patients continued the treatment started for ≥1 year. The mean number of different prescription drugs at baseline ranged from 8–10 across the groups. More than one-half of patients took opioids and one-third took benzodiazepines, sleep disorder drugs, and muscle relaxants.

Conclusion: Patients who started 1 of the 4 common drugs for fibromyalgia similarly had multiple comorbidities and other fibromyalgia-related medication use, but continued the treatment only for a short time. The dose of the 4 drugs was not increased in most patients during the followup period.

Figure 1. Selection of Study Cohort

Our final study cohort included 13,404 amitriptyline, 18,420 duloxetine, 23,268 gabapentin, and 19,286 pregabalin initiators with fibromyalgia.

Figure 2. Proportion of patients remaining on fibromyalgia treatment over time

Approximately 40% of patients started amitriptyline, gabapentin, and pregabalin and 60% of patients started duloxetine continued the treatment for more than 3 months. Less than 20% of patients across the four drug groups remained on the treatment for more than 1 year.

Figure 3. Use (in percentage) of analgesics, sedatives, and muscle relaxants before and after the index date

NSAID: non-steroidal anti-inflammatory drugs including cyclooxygenase -2 inhibitors, BZD: benzodiazepines, M Relax: muscle relaxants