Background/Purpose: To date, no established treatment for chronic pain including fibromyalgia has been specified in Japan. Neurotropin, a non-protein extract isolated from the inflamed cutaneous tissue of vaccinia virus-inoculated rabbits, is often prescribed for mild to severe chronic musculoskeletal pain such as backache, lumbago and stiff neck in Japan. It is also prescribed for fibromyalgia, and its annual overall sales excesses 200 million USD solely in Japan. We conducted a study on efficacy of Neurotropin on chronic pain including fibromyalgia.

Methods: Among 175 patients with chronic pain, Neurotropin was prescribed for 113 patients in whom psychiatric disorders were absent or not contributing to the pain symptom. Of these, 84 patients met both 1990 classification criteria for fibromyalgia by American College of Rheumatology (ACR) and 2010 preliminary diagnostic criteria for fibromyalgia also proposed by ACR. The mean age of the patients was 51.5 year old (range, 13˜81). All patients were assessed and diagnosed by experienced rheumatologists with necessary laboratory and imaging examinations, and any presence or absence of psychiatric disorders were also assessed by an experienced psychiatrist. Neurotropin was firstly introduced as monotherapy with the mean daily dosage of 15 Neurotropin unit. When the efficacy was insufficient after 1 month intake of Neurotropin, other neuro-modulating medications such as selective serotonin reuptake inhibitors (SSRI), serotonin-noradrenaline reuptake inhibitor (SNRI), tricyclic anti-depressants (TCA) and clonazepam were added. Intravenous tramadol was administered only when pain relief by above drugs were insufficient. The degree of pain was assessed by 10cm VAS scale (0, no pain; 10, the worst pain that the patient had ever experienced), and the efficacy was rated as “good”, 50% or greater improvement in VAS scale at the final evaluation; “fair”, 20% – 50% improvement; and “poor”, less than 20% improvement or worsening. Correlation between the dosage of Neurotropin and outcome was studied by Spearman’s rank correlation test.

Results: After 1 month of Neurotropin intake, 23 patients expected to continue it as monotherapy but remaining 90 patients needed additional medications. Among 23 patients with monotherapy, the efficacy was “good” in 14 patients, “fair” in 6, and “poor” in 3. In the remaining 90 patients, the concomitant drugs were SSRI in 18 patients, SNRI in 4, TCA in 37 and clonazepam in 31. Then, only when these combined therapy of oral neuro-modulating drugs failed, intravenous tramadol was administered in 16 patients. Finally, the overall efficacy of Neurotropin was rated as “good” in 63 patients, “fair” in 39, and “poor” in 11, and its dosage and outcome demonstrated significant correlation either in total (p=0.0416), or in monotherapy (p=0.0073).

Conclusion: Neurotropin, a novel neuro-modulating drug which activates the descending inhibitory system from brain to peripheral nerve, was effective for the treatment of fibromyalgia and chronic pain.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-potential-use-of-neurotropintm-a-novel-neuro-modulating-medication-for-the-treatment-of-chronic-pain-and-fibromyalgia/