Quetiapine extended-release (Seroquel-XR) versus amitriptyline monotherapy for treating patients with fibromyalgia: a 16-week, randomized, flexible-dose, open-label trial

Previous open-label studies have suggested that quetiapine could be a valuable alternative for treating fibromyalgia. This study aims to compare the efficacy and tolerability of extended-release quetiapine with amitriptyline for treating fibromyalgia. This study was a randomized, open-label, flexible-dose, non-inferiority trial. Patients with fibromyalgia were randomized to receive quetiapine extended-release (XR) (N = 45) (50 to 300 mg daily) or amitriptyline (N = 45) (10 to 75 mg daily) for 16 weeks. The primary endpoint was the change from baseline to endpoint in the Fibromyalgia Impact Questionnaire (FIQ) total score; the non-inferiority threshold was established at 8 points. The secondary outcomes included sleep quality, anxiety, depression, and quality of life. Twenty-two (49 %) patients in the quetiapine group and 34 (76 %) patients in the amitriptyline group completed the study. We found a reduction of 9.8 points in the total FIQ score at the endpoint for the quetiapine-treated patients compared to 13.9 points for the amitriptyline-treated patients, for a difference of 4.14 points (80 % confidence interval (CI) -0.70 to 8.98). No significant differences were found between the quetiapine XR and amitriptyline groups for any of the secondary outcomes. The proportion of patients discontinuing treatment due to adverse events was higher in the quetiapine group (n = 14, 31.1 %) than the amitriptyline group (n = 3, 6.6 %). Our results appear to indicate that quetiapine XR does not provide similar efficacy to amitriptyline for treating patients with fibromyalgia. Quetiapine XR had a worse tolerability than amitriptyline in this population, possibly due to a relatively high starting dose.