SAN DIEGO – Low-dose naltrexone and repeated visits to the hyperbaric oxygen chamber are two novel potential therapies for fibromyalgia that showed promise in separate studies presented at the annual meeting of the American College of Rheumatology.
The impetus for investigating these unconventional treatments lies in recognition that fibromyalgia is challenging to treat. The Food and Drug Administration–approved medications for this common condition – duloxetine (Cymbalta), pregabalin (Lyrica), and milnacipran (Savella) – often provide inadequate results.
Naltrexone is an opioid receptor antagonist indicated for the treatment of alcohol or opioid dependence. Dr. Daniel G. Arkfeld explained the therapeutic rationale for its use in fibromyalgia thusly: Fibromyalgia has been classified as a CNS sensitization syndrome mediated by proinflammatory cytokines, and naltrexone has been shown to suppress such centrally acting cytokines.
He presented a prospective, open-label, single-center, uncontrolled pilot study involving 25 patients with fibromyalgia diagnosed by ACR criteria. They were started on oral naltrexone at 3 mg at night, with titration up to 4.5 mg. Patients were permitted to continue on their FDA-approved medications for fibromyalgia, and 18 of the 25 did so. The other 7 patients were on naltrexone monotherapy for the study duration.
Twenty-two patients completed the 3-month study. Two dropped out because they deemed naltrexone to be ineffective and one patient quit because of diarrhea.
The primary study endpoint was change in the Revised Fibromyalgia Impact Questionnaire (FIQR) after 90 days on naltrexone. Overall, study participants improved their FIQR scores by an average of 19.5%. However, 11 of the 22 study completers displayed a more robust response, with an average 41% improvement in the metric, according to Dr. Arkfeld, a rheumatologist at the University of Southern California, Los Angeles.
"Naltrexone is dosed once daily and is inexpensive, making it a viable treatment in fibromyalgia," he concluded.
Controlled clinical trials are planned.
Separately, Dr. Shai Efrati presented a randomized, prospective, controlled clinical trial of hyperbaric oxygen therapy in 60 women with fibromyalgia of at least 2 years duration. The therapeutic rationale lies in an earlier randomized trial by Dr. Efrati and coworkers demonstrating that hyperbaric oxygen therapy induced late neuroplasticity in post-stroke patients (PLoS One 2013; 8:e53716).
Thirty fibromyalgia patients commenced an 8-week course of hyperbaric oxygen therapy consisting of five 90-minute sessions per week involving 100% oxygen at 2 atmospheres absolute. After an 8-week hiatus with no treatment, the other 30 patients embarked on the same protocol.
The baseline tender joint count was 17 out of a possible 18 in the first 30 patients; after completion of the 40 treatment sessions, the tender joint count dropped to 9. Similarly, in the second 30-patient cohort, the baseline tender joint count was 17. It remained at 17 at the end of the no-treatment period and dropped to 5 after the course of hyperbaric oxygen therapy. Scores on the FIQR also dropped significantly from baseline to post treatment in both cohorts, reported Dr. Efrati of Assaf Harofeh Medical Center, Zerifin, Israel.
Dr. Arkfeld and Dr. Efrati reported having no financial conflicts of interest regarding their studies, which were free of commercial sponsorship.