A consistent line of investigation proposes that fibromyalgia is a sympathetically maintained neuropathic pain syndrome. Dorsal root ganglia sodium channels may play a major role in fibromyalgia pain transmission. Ambroxol is a secretolytic agent used in the treatment of various airway disorders. Recently, it was discovered that this compound is also an efficient sodium channel blocker with potent anti-neuropathic pain properties. We evaluated the add-on effect of ambroxol to the treatment of fibromyalgia. We studied 25 patients with fibromyalgia. Ambroxol was prescribed at the usual clinical dose of 30 mg PO 3 times a day × 1 month. At the beginning and at the end of the study, all participants filled out the Revised Fibromyalgia Impact Questionnaire (FIQ-R) and the 2010 ACR diagnostic criteria including the widespread pain index (WPI). At the end of the study, FIQ-R decreased from a baseline value of 62 ± 15 to 51 ± 19 (p = 0.013). Pain visual analogue scale decreased from 77 ± 14 to 56 ± 30 (p = 0.018). WPI diminished from 14.6 ± 3.1 to 10.4 ± 5.3 (p = 0.001). Side effects were minor. In this pilot study, the use of ambroxol was associated to decreased fibromyalgia pain and improved fibromyalgia symptoms. The open nature of our study does not allow extracting the placebo effect from the positive results. The drug was well tolerated. Ambroxol newly recognized pharmacological properties could theoretically interfere with fibromyalgia pain pathways. Dose escalating-controlled studies seem warranted.
Keywords: Ambroxol; Dorsal root ganglia; Fibromyalgia; Neuropathic pain; Sodium channels.