BACKGROUND: Common symptoms of fibromyalgia include chronic musculoskeletal pain and stiffness, fatigue, disrupted sleep, and tenderness over specific trigger points. Although commonly used for other chronic pain conditions, the efficacy of antidepressants for fibromyalgia is not well established. Also unclear is whether any benefit is independent of their effect on depression.
DATASOURCES: Forty-one articles comparing antidepressants with placebo for treating fibromyalgia were identified through a search of MEDLINE, PSYCLIT, EMBASE, FEDRIP, The Cochrane Library, and the reference list of retrieved articles. Sixteen of these were randomized placebo-controlled clinical trials reporting measurable outcomes. Two additional trials were excluded because the data were not extractable and another because it was a report of N-of-1 trials.
STUDY DESIGN AND VALIDITY: All of the potential articles were reviewed for inclusion in duplicate with strong inter-rater agreement. Each of the final 13 articles was assessed for quality by more than one person using an instrument developed by Jadad. The mean quality score was high at 5.6 (range=0-8). The authors listed the validity concerns of each article but did not exclude any of them. Since the studies were similar in terms of design, demographics, inclusion criteria, and outcomes assessment, the authors concluded quantitative pooling of the effects of antidepressants was appropriate. No effect of year of publication, study design, quality score, or drug class was found using meta-regression.
OUTCOMES MEASURED: The primary outcome was whether a patient was “improved” with therapy. Other outcomes included pain, fatigue, sleep disturbance, sense of well-being, and quantity and severity of trigger points. Additionally, the authors looked for any assessment of outcomes independent of the effect of therapy on depression.
RESULTS: From 10 trials with extractable data, the odds ratio for improvement with therapy was 4.2 (95% confidence interval [CI], 2.6-6.8). The number needed to treat (NNT) was 4 (95% CI, 2.9-6.3). The individual symptoms of pain, fatigue, sleep disturbance, and well-being showed significant improvements of moderate size, but quantity and severity of trigger points were not statistically different. The sample size was insufficient to draw meaningful conclusions regarding the relative benefit of different classes of antidepressants.
Antidepressants are effective for fibromyalgia, although it remains unclear whether this effect is independent of depression. With treatment, clinicians can expect 1 patient in 4 to improve. Antidepressants can reduce pain, fatigue, and disturbed sleep, and enhance the overall sense of well-being. However, they are not expected to diminish the severity of trigger point tenderness. Since there is more evidence for use of amitriptyline it should be considered first, but SSRIs may be just as effective. Clinicians will have to wait for additional studies to determine which class of antidepressants is most helpful and whether the benefits persist during long-term therapy for this chronic disease.