The impact of prior opioid use on the response to pregabalin in fibromyalgia clinical trials

Fibromyalgia (FM) is a chronic pain disorder for which pregabalin is an approved treatment. While not a recommended treatment option, opioids are used by many FM patients. The impact of prior opioid use on the response to pregabalin treatment in FM has not been assessed. A pooled analysis of four large clinical trials of pregabalin in FM patients was conducted to assess the effect of prior opioid use on the response to treatment. Patients were divided into those using opioids prior to the trial and those who were not. Change in least squares (LS) mean pain score (assessed by 0-10 numeric rating scale, controlled for baseline pain score) in the pregabalin and placebo groups was assessed. There were 2053 patients in the analysis set, including 368 with prior opioid use, with equal numbers treated with placebo, pregabalin 300mg/day and pregabalin 450mg/day. Median duration of opioid use was 1.1 years. Patients ceased opioid use a median of 15.0 days prior to the start of the trial. The LS mean (SE) change in pain score for the placebo group was −0.73 (0.18) with prior opioid use vs. −1.22 (0.08) without, −1.57 (0.18) vs. −1.61 (0.08) with pregabalin 300mg/day, and −1.72 (0.18) vs. −1.89 (0.08) with pregabalin 450mg/day. The treatment effect (LS mean difference from placebo [95% CI]) in patients with and without prior opioid use was 0.85 (0.35-1.35) and 0.39 (0.16-0.63), respectively for pregabalin 300mg/day and 1.00 (0.50-1.50) and 0.66 (0.43-0.90) for pregabalin 450mg/day. Adverse events and discontinuations were also assessed. FM patients with prior opioid use had a greater treatment response to pregabalin compared with placebo. These findings may inform the design of future trials.