Background/Purpose: A consistent line of investigation proposes that fibromyalgia is a sympathetically maintained neuropathic pain syndrome. Moreover it has been suggested that dorsal root ganglia and peripheral sensory neuron sodium channels may play a major role in fibromyalgia pain transmission (BMC Musculoskelet Disord. 2012;13:23). Ambroxol (2-amino-3,5-dibromo-N-[trans-4-hydroxycyclohexyl]benzylamine) is a secretolytic agent used in the treatment of various airway disorders since the late 1970s. More recently it was determined that this compound also has potent anti-neuropathic pain properties. In vitro studies have shown that ambroxol is stronger than lidocaine in sensory neuron sodium channel blockade (Neurosci Lett, 2006;395:179). Furthermore; this medication is effective in the neuropathic pain animal model (Pharmacol Biochem Behav. 2010;97:249). Ambroxol has good safety profile. In many countries this compound is freely dispensed as over-the-counter medication. Our objective was to evaluate the add-on effect of ambroxol in the treatment of fibromyalgia.

Methods: In this one-group pretest-posttest open label pilot clinical observation we recruited 26 patients with fibromyalgia that fulfilled the 2010 ACR diagnostic criteria. The institutional ethics and research committees approved the protocol. Ambroxol was added to the stable pharmacological therapy. Ambroxol was prescribed at the usual clinical dosage of 30 mg PO 3 times a day x 1 month. At the beginning and at the end of the study all participants filled out the following questionnaires: the Revised Fibromyalgia Impact Questionnaire (FIQ-R), the Hospital Anxiety and Depression Scale (HADS), the 2010 ACR diagnostic criteria including the following domains: Widespread Pain Index (WPI), Symptoms Severity Scale (SSS) and Polysymptomatic Distress Scale (PDS).

Results: Patients mean age was 45±10 years. All of them female. At the end of the study; FIQ-R decreased from a baseline value of 62±15.6 to 51.1±18.9 (p = 0.023). VAS for pain decreased from 76.4±14.4 to 56.2±30.4 (p = 0.010). WPI diminished from 14.6±3.0 to 10.4±5.2 (p = 0.001), SSS from 9±4 to 7±2 (p=0.014), PDS from 24±5 to 17±7 (p<0.001). HADS anxiety and depression scores had not significant changes. Side effects were minor and did not required drug withdrawal.

Conclusion: 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 finding controlled studies are warranted.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ambroxol-for-fibromyalgia-one-group-pretest-posttest-open-label-clinical-observation/