A Single-Day Intravenous Ketamine Infusions for Fibromyalgia, a Large Retrospective Study with a Long-Term Assessment

Fibromyalgia is a complex chronic neurosensory disorder that affects approximately 2% of the population. Ketamine acts as a non-competitive antagonist of the N-methyl-D-aspartate receptor, which plays a crucial role in nociceptive hypersensitivity. Small studies, case reports and several randomized studies demonstrated substantial reductions in pain. However, these studies enrolled few participants (between 11 and 34), and did not report on repeated infusions over prolonged periods of time. Here, we describe a large real-world retrospective assessment of repeated IV ketamine infusions for severe fibromyalgia pain.

A total of 92 consecutive patients were treated with repeated single-day intravenous (IV) ketamine infusions for fibromyalgia. Outcome data were collected and analyzed. Patients received approximately 1.5 mg/kg/hour of ketamine during a 3-hour infusion session, repeated as needed every 3-10 months (median interval of 6 months). Data were summarized using descriptive statistics for continuous variables.

Ninety-two female patients, aged 24-78 years (median age 49 years) with median BMI of 32.4, received repeated ketamine infusions for the management of fibromyalgia pain. Thirty-three of the 92 patients were receiving opioids at baseline, with a median morphine sulfate equivalent (MSO4) dose of 30 mg daily. Patients received between 1 and 32 infusions, averaging one infusion every 6 months. The median baseline pain score was 8, which decreased to 5 at the 3-month follow-up and remained stable at 5 through 24 months. At 3 months, 32 of 92 patients reported greater than 50% pain relief, and 30 of 92 at 24 months. Nineteen patients reported minimal or no benefit from treatment. The number of patients receiving opioids decreased from 33 at baseline to 27 at 24-month.

Ketamine infusions provided substantial and sustained pain relief in the majority of patients with fibromyalgia. Repeated ketamine infusions were associated with consistent pain reduction over a 24-month period.