Intravenous lidocaine does not provide additional pain reduction beyond placebo in probable nociplastic chronic low back pain: a randomized controlled equivalence trial

Abstract Importance Evidence supporting repeated intravenous lidocaine infusions for probable nociplastic chronic non-specific low back pain remains limited despite its use as a centrally acting analgesic in several chronic pain conditions. Objective To evaluate whether repeated intravenous lidocaine infusions provide clinically meaningful benefit beyond placebo for pain reduction in probable nociplastic chronic non-specific low back pain. Setting Department of Physical Medicine and Rehabilitation, NRS Medical College and Hospital. Participants Eighty-four adults with chronic non-specific low back pain and probable nociplastic pain features. Interventions Participants were randomized equally to receive either intravenous lidocaine (1 mg/kg bolus followed by 4 mg/kg infusion weekly for 4 weeks) or placebo saline infusion. All participants received background multimodal pain management consisting of amitriptyline and aerobic exercise. Main Outcomes The primary endpoint was the between-group difference in Visual Analogue Scale (VAS) pain intensity at 3 months. Therapeutic equivalence was assessed using a prespecified equivalence margin of ±1.5 VAS units and the two one-sided tests (TOST) framework. Secondary outcomes included sleep quality (Pittsburgh Sleep Quality Index [PSQI]) and functional disability (Quebec Back Pain Disability Scale [QBPDS]). Results At 3 months, the between-group difference in VAS was 0.24 (90% CI, −0.33 to 0.81), entirely within the predefined equivalence bounds, confirming therapeutic equivalence (TOST P < .001). Both groups improved significantly over time without a significant group × time interaction. Improvement in sleep quality was greater in the lidocaine group (mean difference in change score, 1.81; 95% CI, 0.49-3.14; P = .027). Functional improvement numerically favored lidocaine, although continuous disability outcomes were not significantly different. Adverse events were more common in the lidocaine group but were mild, transient, and self-limiting. Conclusion Repeated intravenous lidocaine infusions did not provide additional analgesic benefit over saline infusions administered alongside multimodal pain management in patients with probable nociplastic chronic non-specific low back pain. Relevance These findings support prioritizing evidence-based multimodal pain management, including exercise and centrally acting pharmacological therapy, over routine adjunctive intravenous lidocaine for probable nociplastic chronic non-specific low back pain. Clinical trial registration number CTRI/2024/07/070888. Clinical trials Registry-India (CTRI) https://ctri.nic.in/Clinicaltrials/pmaindet2.php?EncHid=MTA4ODk1&Enc=&userName=.