Preliminary results from a randomized, controlled, cross-over trial of intrathecal oxytocin for neuropathic pain

Objective Compare intrathecal oxytocin, 100 mu g to placebo on ongoing neuropathic pain and mechanical hyperalgesia and allodynia. Study design Randomized, controlled, double-blind cross-over Setting Clinical research unit Subjects Individuals aged 18 to 70 years with neuropathic pain for at least 6 months. Methods Individuals received intrathecal injections of oxytocin and saline, separated by at least 7 days, and ongoing pain in neuropathic area (VAS [visual analog scale]) and areas of hypersensitivity to von Frey filament and cotton wisp brushing were measured for 4 hours. Primary outcome was VAS pain in the first 4 hours after injection, analyzed by linear mixed effects model. Secondary outcomes were verbal pain intensity scores at daily intervals for 7 days and areas of hypersensitivity and elicited pain for 4 hours after injections. Results The study was stopped early after completion of 5 of 40 subjects planned due to slow recruitment and funding limitations. Pain intensity prior to injection was 4.75 +/- 0.99 and modeled pain intensity decreased more after oxytocin than placebo to 1.61 +/- 0.87 and 2.49 +/- 0.87, respectively (P = .003). Daily pain scores were lower in the week following injection of oxytocin than saline (2.53 +/- 0.89 vs 3.66 +/- 0.89; P = .001). Allodynic area decreased by 11%, but hyperalgesic area increased by 18% after oxytocin compared to placebo. There were no study drug related adverse effects. Conclusion Although limited by the small number of subjects studied, oxytocin reduced pain more than placebo in all subjects. Further study of spinal oxytocin in this population is warranted.

Automated summary

This study compared the effects of intrathecal oxytocin and placebo on neuropathic pain and mechanical hyperalgesia. The results showed that oxytocin reduced pain intensity more than placebo, but also increased the hyperalgesic area. Although limited by the small sample size, further research on spinal oxytocin in this population is warranted.