Does a Single Dose of Adenosine in Epidural Space Reduce Cancer-Related Neuropathic Pain? A Randomized Clinical Trial

[Background]Systemic and intrathecal adenosine reduce chronic neuropathic and nociceptive pain; however, the effect of adenosine epidural injection in the treatment of neuropathic cancer-related pains remains unclear.[Objectives]The objective of this study was to evaluate the efficacy of a single epidural administration of adenosine in alleviating chronic neuropathic pain in patients with primitive neuroectodermal tumors.[Methods]In this single-blind randomized clinical trial with the unique ID of IRCT2017031428878N1, 88 patients with chronic neuropathic pain were divided into two equivalent groups. Two groups were treated with a single dose epidural administration of ropivacaine, 0.75 mL/kg from 0.2% solution (both groups), plus adenosine, 50 mcgr/kg (adenosine group), or normal saline (control group). Patients were evaluated on the days 1, 2, 3, 5, 7, 10, and 14 after injection.[Results]Both groups showed a reduction in pain severity according to verbal rating scale (VRS) (3 ± 0.09-1 ± 0.05 in adenosine, 4 ± 0.08-1 ± 0.00 in the control group) and visual analogue scale (VAS) (7 ± 0.25-1 ± 0.12 in adenosine, 8 ± 0.22-1 ± 0.06 in the control group); however, this reduction was significantly higher in the control group (P < 0.0005). The intensity of neuropathic pain decreased in both groups according to Douleur Neuropathique 4 questions (DN4) scores (from 5 ± 0.23-1 ± 0.04 in adenosine group, and from 5.5 ± 0.24-1 ± 0.00 in the control group) without a significant difference between the groups (P = 0.19). Adenosine group had less nausea and vomiting (P < 0.0005).There was no significant difference in patient satisfaction levels between adenosine and control groups (P = 0.09).[Conclusions]Administration of bolus epidural adenosine is not effective in reducing neuropathic pain in patients with primitive neuroectodermal tumors.