Hui-Min Hu ^1,2* Wen-Hui Liu ^1,2 Chen Li ^1,2* Qing Shi ^1,2* Chun-Hua Liu ^1,2* An-Xiang Liu ^1,2* Yi-Fan Li ^2* Yi Zhan ^2* Peng Mao ^2* Bi-Fa Fan ^2*

• ¹ Beijing University of Chinese Medicine, Beijing, China
• ² Department of Pain Management, China-Japan Friendship Hospital, Beijing, China

Purpose: Postherpetic neuralgia (PHN) is a type of refractory neuropathic pain that causes significant suffering, disability, economic loss, and medical burden. In this study, we aim to evaluate the efficacy and safety of interferon (IFN)-α1b injection into the intervertebral foramen of patients with PHN. Patients and Methods: This is a study protocol for a randomized, double-blind placebocontrolled multicenter clinical trial. A total of 200 participants with PHN from 11 hospitals will be recruited and randomly assigned to the treatment group administered with IFN-α1b and control group treated with placebo in a 1:1 ratio. Both groups will also receive oral pregabalin 150 mg twice daily and lidocaine injection into the intervertebral foramen as conventional therapy. This trial will involve a screening period, a 2-week intervention, and a 3-month follow-up. The primary outcomes will include the visual analog scale score and duration of pain relief. The secondary outcomes will include the 36-item short-form, dosage and duration of painkillers taken, viral load of varicella-zoster virus DNA, humoral cytokine level, and dosage and frequency of rescue medication. All adverse events and severe adverse events will be assessed during the study. Conclusion: This study is expected to 2 provide evidence for the efficacy and safety of IFN-α1b injection into the intervertebral foramen in patients with PHN. Trial Registration: This study has been registered in the Chinese Clinical Trial Registry (ChiCTR) under the identification code ChiCTR2400089962.