Effect of Intravenous Lidocaine Associated With Amitriptyline on Pain Relief and Plasma Serotonin, Norepinephrine, and Dopamine Concentrations in Fibromyalgia

Abstract

The objective of this study was to evaluate the effect of intravenous lidocaine combined with amitriptyline on pain relief and plasma serotonin, norepinephrine, and dopamine levels. A prospective, randomized, double-blind comparative study was conducted in 30 patients. All patients received 25 mg amitriptyline; monotherapy group (n=15) received 125 mL saline, and combined therapy group (n=15) received 240 mg lidocaine in 125 mL saline once a week for 4 weeks. Serotonin, norepinephrine, and dopamine were measured in plasma at time zero (T0) and after 4 weeks (T4). Pain intensity was rated on a numerical scale at the beginning of the study and weekly for 4 weeks. All patients were females and the mean age was 44.7±10.5 years for monotherapy group and 40.9±11.6 years for combined therapy group. No difference in pain intensity at baseline was observed between groups, with a decrease after treatment in monotherapy group (T0: 7.0±1.2 and T4: 4.0±2.1) and in combined therapy group (T0: 7.6±0.8 and T4: 4.1±2.3). Plasma serotonin and norepinephrine levels were similar in the 2 groups at T0 and T4. An increase in dopamine levels was observed in monotherapy group from the beginning to the end of treatment. Combined administration of 240 mg intravenous lidocaine (once a week) and 25 mg amitriptyline for 4 weeks did not modify pain intensity or plasma serotonin, norepinephrine, or dopamine concentrations in fibromyalgia patients.