Background/Purpose In a prior study in fibromyalgia (FM) patients taking an antidepressant for their comorbid depression, pregabalin (PGB) significantly reduced pain severity (treatment difference compared with placebo [95% CI], –0.61 [–0.91 to –0.31]). However, the effect of patients’ baseline clinical characteristics on the treatment response to pregabalin has not previously been examined.

Methods In the randomized, placebo (PBO)-controlled, 2-way crossover study, patients with FM aged ≥18 years taking a single antidepressant for their comorbid depression were randomized 1:1 to PGB (300 or 450 mg/d)/PBO or PBO/PGB. Treatment was for two 6-week periods, separated by a 2-week taper/washout. Antidepressant medication (SSRI or SNRI) was continued throughout the study. Endpoint mean pain scores (by 11-point numeric rating scale) were pooled from the two treatment periods. In this analysis, the effect of the following baseline clinical characteristics on endpoint mean pain scores was examined: pain severity (moderate, pain score of 4 to ≤7; severe, 7 to 10); depression diagnosis (major depressive disorder [MDD] or depression not otherwise specified [NOS]); prior or no prior opioid use; and Hospital Anxiety and Depression Scale-Anxiety (HADS-A) or -Depression (HADS-D) score (0-21 scale). Variables were analysed as fixed factors in a linear mixed effects model including sequence, period, and treatment as fixed factors, and subject within sequence and within subject error as random factors. 

Results A total of 193 patients were included in the analysis; 181 received ≥1 dose of PGB and 177 PBO. Mean age was 50.1 years and 93.3% of patients were female. Mean (median) pain, HADS-A, and HADS-D scores at baseline were 6.7 (6.9) 8.3 (8.0), and 8.0 (8.0), respectively. Endpoint mean pain scores were significantly lower (P < 0.05) with PGB compared with PBO (treatment difference, 95% CI) irrespective of patients having: moderate (–0.62, –1.06 to –0.17; n = 104) or severe (–0.53, –0.93 to –0.14; n = 89) pain; diagnosis of MDD (–0.73, –1.22 to –0.24; n = 84) or depression NOS (–0.54, –0.94 to –0.13; n = 101); prior (–0.70, –1.35 to –0.05; n = 44) or no prior opioid use (–0.53, –0.88 to –0.19; n = 149); HADS-A score <8 (–0.55, –1.08 to –0.02; n = 86) or ≥8 (–0.67, –1.04 to –0.31; n = 107); or HADS-D score <8 (–0.93, –1.44 to –0.42; n = 85). However, while there was a trend towards improvement with pregabalin in patients with HADS-D score ≥8, this was not significant (–0.31, –0.67 to 0.06; P = 0.098; n = 108).

Conclusion In patients with FM taking an antidepressant for comorbid depression, pregabalin significantly improved mean pain scores irrespective of baseline pain severity, depression diagnosis, prior opioid use, or HADS-A score. This study has important clinical implications in that pregabalin improved pain in FM patients with a wide range of baseline clinical characteristics.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/understanding-baseline-clinical-characteristics-may-be-of-use-in-considering-the-response-to-pregabalin-in-fm-patients-with-comorbid-depression/