This randomized double-blind, active placebo-controlled trial (n=24) investigates the analgesic efficacy of esketamine on fibromyalgia pain. The study found short-term pain reduction in the ketamine group but no significant differences in treatment effects on pain scores during the 2.5-hour or the 8-week follow-up, suggesting that a short-term infusion of ketamine is insufficient for long-term analgesic effects in fibromyalgia patients.
Abstract of Absence of long-term analgesic effect from a short-term S-ketamine infusion on fibromyalgia pain
“To assess the analgesic efficacy of the N-methyl-D-aspartate receptor antagonist S(+)-ketamine on fibromyalgia pain, the authors performed a randomized double blind, active placebo-controlled trial. Twenty-four fibromyalgia patients were randomized to receive a 30-min intravenous infusion with S(+)-ketamine (total dose 0.5 mg/kg, n = 12) or the active placebo, midazolam (5 mg, n = 12). Visual Analogue Pain Scores (VAS) and ketamine plasma samples were obtained for 2.5-h following termination of treatment; pain scores derived from the fibromyalgia impact questionnaire (FIQ) were collected weekly during an 8-week follow-up. Fifteen min after termination of infusion the number of patients showing a reduction in pain scores >50% was 8 vs. 3 (P < 0.05), at t = 180 min 6 vs. 2 (ns), at the end of week-1 2 vs. 0 (ns) and at end of week-8 2 vs. 2 in the ketamine and midazolam groups, respectively. Ketamine effect on VAS closely followed ketamine plasma concentrations. For VAS and FIQ scores no significant differences in treatment effects were observed in the 2.5-h following infusion or during the 8-week follow-up. Side effects as measured by the Bowdle questionnaire (which scores for 13 separate psychedelic symptoms) were mild to moderate in both study groups and declined rapidly, indicating adequate blinding of treatments. Efficacy of ketamine was limited and restricted in duration to its pharmacokinetics. The authors argue that a short-term infusion of ketamine is insufficient to induce long-term analgesic effects in fibromyalgia patients.”
Authors: Ingeborg Noppers, Marieke Niesters, Maarten Swartjes, Martin Bauer, Leon Aarts, Natasja Geleijnse, René Mooren, Albert Dahan & Elise Sarton
Summary of Absence of long-term analgesic effect from a short-term S-ketamine infusion on fibromyalgia pain
Fibromyalgia is characterized by chronic generalized musculoskeletal pain without a specific structural or inflammatory cause. It has been associated with central sensitization, most importantly NMDAR activation and up regulation at spinal and supraspinal sites.
In the current study the authors investigated the effect of a short-term esketamine infusion on fibromyalgia pain. Earlier studies found that the effect of the infusion lasted for 24 h or longer in patients with Complex Regional Pain Syndrome type 1 (CRPS1) and in therapy resistant major depression.
The authors recruited patients after protocol approval was obtained from the local ethics committee. They hypothesized that ketamine causes greater pain relief than placebo, and induces pain relief beyond the treatment period.
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https://doi.org/10.1016/j.ejpain.2011.03.008
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Noppers, I., Niesters, M., Swartjes, M., Bauer, M., Aarts, L., Geleijnse, N., ... & Sarton, E. (2011). Absence of long-term analgesic effect from a short-term S-ketamine infusion on fibromyalgia pain: a randomized, prospective, double blind, active placebo-controlled trial. European Journal of Pain, 15(9), 942-949.