The preliminary results  of a randomized, controlled, double-blind, cross-over study depicted that Oxytocin, administered at a dosage of 100 µg, effectively reduces neuropathic pain. The investigators sought to evaluate the impact of intrathecal administration of Oxytocin compared to a placebo in relation to ongoing neuropathic pain, allodynia, and mechanical hyperalgesia.

People aged between 18 and 70 years, who had been experiencing neuropathic pain for a minimum of six months, underwent two different procedures: intrathecal injections of Oxytocin and saline. These injections were administered with a gap of a minimum of 7 days between them. The study evaluated the ongoing pain experienced in the neuropathic region using a visual analog scale (VAS) and assessed areas of hypersensitivity by testing responses to von Frey filament and cotton wisp brushing.

These measurements were carried out during a 4-hour time frame. The major endpoint of interest was the VAS pain score during the initial 4 hours following the injection, and this was assessed using a linear mixed effects model. Secondary endpoints included verbal pain intensity scores recorded at daily intervals for 7 days and the assessment of hypersensitive areas and triggered pain over the 4-hour post-injection period.

The study was terminated prematurely after enrolling only 5 out of the initially planned 40 participants due to difficulties in recruiting subjects and funding constraints. Prior to the injection, the pain intensity recorded was 4.75 ± 0.99. Interestingly, the modelled pain intensity declined following the administration of Oxytocin (reducing to 1.61 ± 0.87) compared to the placebo (which reduced to 2.49 ± 0.87).

Furthermore, daily pain scores in the week following the Oxytocin injection were lower when compared to those following the saline injection (2.53 ± 0.89 versus 3.66 ± 0.89). It's worth noting that the allodynic area decreased by 11% after Oxytocin treatment, but there was an 18% rise in the hyperalgesic area when compared to the placebo. Importantly, no adverse effects related to the study drug were reported.

While acknowledging the limitation of a small sample size, it is noteworthy that Oxytocin demonstrated a greater reduction in pain compared to the placebo among all participants. This suggests that additional research involving spinal Oxytocin in this population is needed.