Effects and predictors of intravenous lidocaine infusion for patients with fibromyalgia.

OBJECTIVE

Fibromyalgia is a chronic pain condition characterised by widespread pain. The current treatment primarily focuses on self-management and symptomatic relief. IV lidocaine infusion is the most performed procedure in the UK that is offered after conventional therapy has failed. We aim to identify the predictors of response to systemic lidocaine to enable targeted treatment for individuals who are more likely to benefit.

METHODS

This study adheres to the RECORD guidelines for reporting studies using routinely collected observational data. It was conducted retrospectively and employed data derived from clinical records of patients who received standard care. Adult patients who had completed questionnaires and quantitative sensory testing (QST) before IV lidocaine infusion were included. We collected data consecutively from 132 patients, including 24 men and 108 women. Responders were defined as patients who experienced a pain reduction of 50% or greater lasting for at least three weeks following an IV lidocaine infusion at a dose of 5 mg/kg.

RESULTS

We identified 22% of patients as responders. Our findings indicate a notable gender disparity in the number of responders, with a response rate of 25.9% observed in female patients compared to 4.2% in male patients (p = 0.02). Functional impairment in the revised fibromyalgia impact questionnaire was higher in female patients than male patients (22.6 ± 5.8 vs 19.8 ± 7.7, p = 0.043). Responders were younger (42.7 ± 11.2 vs 49.4 ± 11.4, p = 0.003), had shorter pain duration in years (10.0 ± 6.1 vs 14.1 ± 9.3, p = 0.015), and lower weekly pain scores (7.8 ± 1.7 vs 8.5 ± 1.4, p = 0.014). No significant difference in QST parameters or loss/gain phenotypes was observed between responders and non-responders. A normal QST was identified in 25% of responders and 16% of non-responders. Consequently, QST alone could not predict the response to systemic lidocaine infusion.

CONCLUSIONS

IV lidocaine infusion proves effective, especially for younger female patients, which should be added to conventional therapies for these patients.