Short- and Midterm Analgesic Outcomes of Ketamine Versus Lidocaine Infusion in Chronic Peripheral Neuropathic Pain: A Retrospective Study.

BACKGROUND: Intravenous ketamine and lidocaine infusions are increasingly used for chronic peripheral neuropathic pain, particularly in refractory cases. However, comparative data on their short- and midterm analgesic outcomes in routine clinical practice are limited. METHODS: This retrospective study included patients with chronic peripheral neuropathic pain who received intravenous ketamine or lidocaine infusion between January and May 2021. Ketamine was administered at 1 mg/kg/h and lidocaine at 3 mg/kg/h for five consecutive days. Pain intensity and neuropathic pain features were assessed using the Numeric Rating Scale (NRS) and the Douleur Neuropathique 4 (DN4) questionnaire at baseline and at 2 weeks, 2 months, and 6 months after treatment. Clinically meaningful pain relief was defined as a ≥ 50% reduction in pain scores. RESULTS: A total of 102 patients were analyzed (ketamine group, n = 44; lidocaine group, n = 58). Both groups showed significant reductions in NRS and DN4 scores at all follow-up points compared with baseline (p < 0.01). Clinically meaningful pain relief was more frequent in the ketamine group at 2 weeks (p < 0.01), whereas no significant differences were observed at 2 and 6 months (p > 0.05). Adverse effects occurred more often with ketamine, while lidocaine was associated with fewer side effects (p < 0.05). CONCLUSION: Ketamine provided a greater early analgesic response at 2 weeks, whereas both treatments demonstrated comparable midterm efficacy at 2 and 6 months. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06297915.