Intrathecal oxytocin for neuropathic pain: A randomized, controlled, cross-over trial

Abstract

AbstractObjectiveTo investigate the effect of intrathecal oxytocin compared to placebo on pain and hypersensitivity in individuals with chronic neuropathic pain.Study designRandomized, controlled, double-blind cross-over studySettingOutpatient clinical research unit.SubjectsIndividuals between ages of 18 and 70 years with neuropathic pain caudal to the umbilicus for at least 6 months.MethodsIndividuals received two blinded intrathecal injections of either oxytocin or saline, separated by at least 7 days, and ongoing neuropathic pain (VAS: visual analog scale) and areas of hypersensitivity were measured at intervals for 4 hours. The primary outcome was VAS pain, analyzed by linear mixed effects model. Secondary outcomes were verbal pain intensity scores at intervals for 7 days and areas of hypersensitivity and elicited pain for 4 hr after injections.ResultsThe 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=0.003). Daily pain scores were lower in the week following injection of oxytocin than saline (2.53 ± 0.89 vs 3.66 ±0.89; p=0.001). Hypersensitivity differed between oxytocin and placebo by small amounts in opposite directions depending on modality tested. There were no study drug related adverse effects.DiscussionAlthough 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.