Effect of Baseline Characteristics on the Pain Response to Pregabalin in Fibromyalgia Patients with Comorbid Depression

Objective. To evaluate the effect of baseline characteristics on the treatment response to pregabalin in fibromyalgia (FM) patients with depression. Design. Post hoc analysis from a randomized, double-blind, placebo-controlled, two-way crossover study of pregabalin (300 or 450mg/day, twice daily). Subjects. A total of 193 FM patients taking an antidepressant for comorbid depression. Methods. The effect of patient baseline characteristics on the treatment response to pregabalin vs placebo was assessed for the primary efficacy end point (mean pain score on an 11-point numeric rating scale). Variables were analyzed using a linear mixed effects model with sequence, period, and treatment as fixed factors, and subject within sequence and within subject error as random factors. Results. Pregabalin significantly improved mean pain scores vs placebo irrespective of age, duration of FM, number of prior FM medications, depression diagnosis, shorter-term depression (<10 years), prior or no prior opioid use, pain severity, anxiety severity, and sleep disruption severity (all P<0.05). Compared with placebo, pregabalin did not significantly affect mean pain scores in patients with comorbid insomnia, irritable bowel syndrome, or gastroesophageal reflux disease; severe FM; a diagnosis of depression before FM, longer-term depression (>= 10 years), more severe depression, or who were taking a high dose of antidepressant. Conclusions. Pregabalin significantly improved mean pain scores when compared with placebo for the majority of baseline characteristics assessed in FM patients taking an antidepressant for comorbid depression.