Gabapentin and pregabalin in the treatment of fibromyalgia: a systematic review and a meta-analysis

What is known and Objectives: Fibromyalgia (FBM) is a common chronic pain disorder affecting up to 2% of the general population. Current treatment options are mostly symptom-based and limited both in efficacy and number. Two promising alternatives are gabapentin (GP) and pregabalin (PB). We aimed to estimate the efficacy and safety/tolerability of the two compounds in FBM through a systematic review and a meta-analysis of relevant randomized double-blind placebo-controlled (RCT) were performed. Data sources, extraction and analysis: A literature search was conducted through MEDLINE, EMBASE, Cochrane CENTRAL and the reference lists of relevant studies. Responders to treatment (>30% reduction in mean pain score) and dropouts due to lack of efficacy were used as primary outcome measures. Dropout rates and incidence of common adverse outcomes were also investigated. Four RCTs, reporting data on 2040 patients, were reviewed and three of them using PG were included in the meta-analysis. Results: Pregabalin at a dose of 600, 450 and 300 mg per day is effective in FBM compared to placebo (NNT: 7, upper 95% CI: 12, 450 mg). A number of adverse events (AE), such as dizziness, somnolence, dry mouth, weight gain, peripheral oedema, is consistently associated with treatment at any dose and could lead one out of four patients to quit treatment (NNH: 6, lower 95% CI: 4, 600 mg). Indirect comparison meta-analysis suggests that PB at a dose of 450 mg per day could result in more responders than at 300 mg, but this result needs to be interpreted with caution as there were no significant differences between 600 and 300 mg or between 600 and 450 mg. Data on GP is limited. What is new and Conclusions: The analysis indicates that PB at a dose of 450 mg per day is most likely effective in treating FBM, although AE are not negligible. Further evidence is necessary for more conclusive inferences.