Ketamine in fibromyalgia: a systematic review.

Objective: Fibromyalgia (FM) subjects are treated with antidepressant agents; in most cases, these drugs lose efficacy or have adverse effects. Ketamine is an anesthetic drug used in FM in some studies. This article aims to systematically review the safety and efficacy of ketamine in fibromyalgia (FM) patients.

Materials and methods: We systematically searched articles on FM and ketamine published at Pubmed from 1966 to 2021. This study was registered at PROSPERO.

Results: There were only 6 articles published in this field, with a total of 115 patients. The female sex was predominant (88 to 100%). The age varied from 23 to 53 years old. Disease duration ranged from 1 month to 28 years. The dosage of ketamine changed from 0.1 mg/kg-0.3-0.5 mg/kg in intravenous infusion (4/5) and subcutaneous application (1/5). Regarding outcomes, the Visual analog scale (VAS) before ketamine was from 59 to 100 mm and after treatment from 2 to 95 mm. Most short-term studies had a good response. Only the study with 8 weeks of follow-up did not observe a good response. Side effects were common; all appeared during the infusion and disappeared after a few minutes of the ketamine injection.

Conclusions: The present study demonstrates the effectiveness and safety of ketamine in FM patients in the short term. Although, more studies, including long-term follow-up studies, are still needed.