Repeated Intravenous Lidocaine Infusions for Patients with Fibromyalgia: Higher Doses of Lidocaine Have a Stronger and Longer-Lasting Effect on Pain Reduction.

Abstract

To determine the effect of escalating doses of lidocaine infusion with or without added magnesium on pain levels and the duration of pain relief in patients with fibromyalgia (FM). A retrospective chart review of 74 patients diagnosed with FM who underwent at least three escalating doses of intravenous (IV) lidocaine infusions (5 mg/kg of body weight, 7.5 mg/kg, and 7.5 mg/kg of lidocaine + 2.5 g of magnesium sulfate) was conducted. Each patient's subjective impression of change in pain intensity and duration of pain relief after each treatment was recorded, along with an 11-point numeric rating scale (NRS) for pain intensity, immediately before and after each infusion. Short-term lidocaine analgesia was evaluated by the reduction in NRS pain score according to the patients reported pre- (immediately before treatment) and post-treatment (immediately after treatment) values. There was a statistical difference in the NRS score reduction between doses 5 mg/kg and 7.5 mg/kg of lidocaine (P = 0.009). Long-term analgesia was evaluated at follow-up visits by the patient's subjective impression of change in pain intensity and duration of pain relief. There was a statistical difference in the percentage of pain relief and the mean duration of pain relief between the treatments with 5 mg/kg and 7.5 mg/kg of lidocaine (P = 0.007 and P = 0.003). Although there was a trend of greater response to magnesium sulfate as a beneficial adjunct to the lidocaine infusion, we were unable to find a statistically significant difference for any of the variables studied. This study demonstrated that escalating doses of IV lidocaine to 7.5 mg/kg safely and effectively reduced the pain with prolonged effect in a significant number of patients diagnosed with fibromyalgia. Larger, prospective clinical studies are required to confirm this finding.