Analgesic efficacy of intravenous lidocaine vs ketamine in refractory chronic pain: a retrospective analytic study with 3-month follow-up

BACKGROUND: Refractory chronic pain conditions remain challenging to manage, and intravenous infusions of ketamine, lidocaine, or their combination have emerged as potential therapeutic options. OBJECTIVE: To evaluate the analgesic effectiveness and safety of intravenous lidocaine, ketamine, and their combination in patients with refractory chronic pain. METHODS: We conducted a retrospective analytic study of patients treated between January 2020 and November 2024 at an outpatient pain clinic. Eligible patients had persistent severe pain (numerical rating scale [NRS] > 6/10) despite ≥3 months of multimodal pain management and received intravenous lidocaine, ketamine, or combination infusions. The primary outcome was immediate pain reduction post-infusion. Secondary outcomes included pain relief at 1 and 3 months, quality of life (QoL) assessed by EQ-5D-5L, and associations between clinical characteristics and treatment response. RESULTS: A total of 120 patients were included. All 3 groups demonstrated significant reductions in NRS scores from baseline after the first infusion, with mean differences of 3.09 (95% CI 2.56-3.62) for lidocaine, 2.30 (95% CI 1.48-3.13) for ketamine, and 3.95 (95% CI 3.33-4.57) for combination therapy. Analgesic effects persisted at 1- and 3-month follow-up. Mild, self-limiting adverse effects occurred in 7.5% of patients. The combination group showed superior pain reduction at selected time points and greater improvements in QoL at 3 months. CONCLUSIONS: Intravenous lidocaine, ketamine, and combination infusions provide immediate and sustained pain relief in refractory chronic pain. Combination therapy may offer additional benefit beyond monotherapy, supporting its consideration in clinical practice.