VetSRev
Database of veterinary systematic reviews
Database of veterinary systematic reviews
Pain (2021) :
DOI: 10.1097/j.pain.0000000000002231
In humans, proof of long-term efficacy of ketamine treatment in neuropathic pain is lacking. To improve our understanding of ketamine behavior under various administration conditions, we performed a systematic review and meta-analyses of controlled studies on the efficacy of ketamine in mice and rats with a disease model of nerve injury on relief of allodynia. Searches in PubMed and EMBASE identified 31 unique studies. Four meta-analyses were conducted. The first analysis included 19 comparisons on a single ketamine dose and measurement of effect within 3 hours of dosing and showed an appreciable effect (standardized mean difference 1.6, 95% confidence interval 1.1-2.1). Subgroup analyses showed no effect of species, administration route, or dose. A single administration was insufficient to sustain relief of allodynia at 24 or 72 hours after dosing, as observed in our second analysis (7 comparisons) with similar effects in ketamine-treated and control animals. Chronic ketamine administration (9 comparisons) caused profound relief of allodynia when tested during ketamine exposure (effect size 5.1, 3.7-6.5). The final analysis (6 comparisons) showed that chronic administration caused a slow loss of relief of allodynia with 70% loss of effect 24 days after end of treatment. No subgroups analyses were possible in the last 3 meta-analyses due to small group sizes. These results indicate long-term ketamine anti-allodynic effects after chronic exposure (\textgreater3 days) but not after a single administration. Given several limitations, extrapolation of the animal data to the human condition is tenuous.
Velzen, M. V., Dahan, J. D. C., van Dorp, E. L. A., Mogil, J. S., Hooijmans, C. R., & Dahan, A. (2021). Efficacy of ketamine in relieving neuropathic pain: a systematic review and meta-analysis of animal studies. Pain. https://doi.org/10.1097/j.pain.0000000000002231