Duloxetine as a treatment for Fibromyalgia Syndrome

Another article has been published concluding that Duloxetine is beneficial in the treatment of Fibromyalgia Syndrome (Fibro). [1]

Duloxetine is a new selective serotonin and norepinephrine reuptake inhibitor (SNRI) that is licensed for the treatment of pain in diabetic neuropathy in the EU. [1] Duloxetine was approved for the treatment of Fibro by the American Food & Drug Administration (FDA) earlier this year.

The recent article discusses two randomized, placebo-controlled trials investigating the short-term safety and efficacy of duloxetine 60 mg/day and 120 mg/day in patients suffering from Fibro over a period of 12 weeks. [1]

Both dosages were found to be superior to placebo in pain relief, and improvement in quality of life and depressive symptoms, although the analgesic effect was largely independent of the antidepressant action of duloxetine. The higher dose of 120 mg/day further reduced the tender point count and elevated the tender point pain thresholds. In both studies, only mild to moderate adverse effects were reported. [1]

Last year, a group of researchers from the University of Cincinnati College of Medicine, Cincinnati, USA published an article examining the pooled results from the two randomized, placebo-controlled clinical trials of Duloxetine as a treatment for Fibro in women who met the American College of Rheumatology criteria for Fibro. [2]

They found that, compared with the patients receiving placebo, duloxetine-treated patients demonstrated a significantly greater improvement in the Brief Pain Inventory (BPI), average pain severity score and in the Fibromyalgia Impact Questionnaire (FIQ) total score, beginning at week 1 and continuing through week 12. Duloxetine was superior to placebo on all efficacy measures, including mean tender point threshold, Clinical Global Impression of Severity, Patient Global Impression of Improvement, and average interference from pain scores. The duloxetine-treated group was superior to placebo on all quality of life and functional measures, including each domain of the Medical Outcomes Study Short Form-36 (SF-36). [2]

A direct treatment effect of duloxetine on pain reduction was demonstrated and shown to be independent of secondary improvement in mood (based on BPI average pain score). [2]

The researchers found that significantly more duloxetine-treated patients reported treatment-emergent adverse events, but the rates of serious adverse events were similar between duloxetine-treated and placebo-treated patients. [2]

Duloxetine 60 mg/day and 120 mg/day has proven to be beneficial in the treatment of the pain and functional impairment associated with Fibro in female patients, while significantly improving quality of life. As is true for other antidepressants further studies are needed to assess the long-term efficacy and safety of duloxetine as an additional pharmacological treatment option in Fibro. [1][2] This is particularly true given research has shown that amitriptyline is not effective as a treatment for Fibro long-term. Amitriptyline, a tricyclic anti-depressants, works in a different way to the SNRIs such as Duloxetine, but they target the same two neurotransmitters: serotonin and norepinephrine. [3]

References:

1. Uçeyler N, Offenbächer M, Petzke F, Häuser W, Sommer C. New treatment options for fibromyalgia: critical appraisal of duloxetine. Neuropsychiatr Dis Treat. 2008 Jun;4(3):525-9.
2. Arnold LM, Pritchett YL, D'Souza DN, Kajdasz DK, Iyengar S, Wernicke JF. Duloxetine for the treatment of fibromyalgia in women: pooled results from two randomized, placebo-controlled clinical trials. J Womens Health (Larchmt). 2007 Oct;16(8):1145-56.
3. Nishishinya B, Urrútia G, Walitt B, Rodriguez A, Bonfill X, Alegre C, Darko G. Amitriptyline in the treatment of fibromyalgia: a systematic review of its efficacy. Rheumatology (Oxford). 2008 Aug 12. [Epub ahead of print]