There is solid evidence supporting the notion that ketamine may have analgesic and antihyperalgesic properties, according to a meta-analysis published in Neurology.

The researchers systematically searched 6 major databases (PubMed, Embase, CENTRAL, CINAHL, PsycINFO, and Web of Science) from inception through March 2018 for studies in which human evoked pain models were used to examine the effects of N-methyl-D-aspartate (NMDA) receptor antagonists compared with no-intervention controls.  A total of 70 trials were selected (n=1069).

Low-dose ketamine (ie, <1 mg/kg) was found to be associated with a decrease in hyperalgesic area (standardized mean difference, 0.54; 95% CI, 0.34-0.74; P <.001) and a 1.2-point decrease in pain ratings from 4.6 to 3.4 on a 0 to 10 numeric rating scale (26% reduction; 95% CI, 0.88-1.44; P <.001). Ketamine was found to have comparable analgesic effects in acute and hyperalgesic models. The effects were constant for doses between 0.03 and 1.00 mg/kg.

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“We found robust evidence that low-dose ketamine (up to 1 mg/kg), but not dextromethorphan, reduces acute pain and hyperalgesia. Dose-response curves also suggest ketamine may be just as effective when administered at the lower end of the subanesthetic dose range,” the researchers noted.

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Reference

Thomspon T, Whiter F, Gallop K, et al. NMDA receptor antagonists and pain relief: a meta-analysis of experimental trials [published online March 6, 2019]. Neurology. doi:10.1212/WNL.0000000000007238