An open-label study of levopromazine (methotrimeprazine) as an add-on therapy in fibromyalgia management

To assess the potential efficacy and tolerability of levopromazine(methotrimeprazine) in the treatment of fibromyalgia.

Unicentre, open-label study conducted in thirty-five outpatients, aged 18 years or older, who met the ACR criteria for fibromyalgia and had not satisfactorily responded to previous fibromyalgia treatment. Levopromazine, flexibly dosed (12.5-100 mg/d), was added to the outpatients' original treatment regimens for 12 weeks. The primary outcome measure was the mean change from baseline to endpoint in the Fibromyalgia Impact Questionnaire (FIQ) total score in the intent-to-treat sample. Secondary outcomes included the Clinical Global Impression (CGI) of Severity scale, Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory, State-Trait Anxiety Inventory, 12-Item Short Form Health Survey, and individual items of the FIQ.

The mean FIQ total score did not decrease significantly at the study endpoint (63.37 SD 11.32 vs. 61.19 SD 9.32, p=0.73). Pain intensity, as evaluated by the Visual Analogue Scale, remained unchanged at study endpoint (8.5 SD 1.6 vs. 8.2 SD 1.2, p=0.49). A statistically significant reduction was observed in the PSQI score (15.65 SD 3.33 vs. 12.23 SD 3.79, p<0.001, effect size: 1.03) and the CGI-severity score (4.71 SD 0.64 vs. 4.03 SD 1.01, p<0.002, effect size: 1.06). No significant or relevant changes were seen in the remaining fibromyalgia symptoms, psychopathological scales or quality-of-life. The drug was well tolerated.

Despite its efficacy in improving sleep quality, levopromazine does not appear to be a useful alternative treatment for fibromyalgia.