Effect of intravenous lidocaine combined with amitriptyline on pain intensity, clinical manifestations and the concentrations of IL-1, IL-6 and IL-8 in patients with fibromyalgia: A randomized double-blind study.

AIM: Regarding the use of intravenous lidocaine in fibromyalgia, there are no well-controlled studies. This study aimed to evaluate the effect of intravenous lidocaine on pain intensity, clinical manifestations and plasma levels of interleukin (IL)-1, IL-6, and IL-8 in fibromyalgia patients.

METHODS: In a randomized double-blind study, group 1 patients received 240 mg of lidocaine in 125 mL of saline solution, while group 2 patients received 125 mL of saline, both once a week for 4 weeks (T1, T2, T3 and T4). All patients received amitriptyline. The following were assessed: pain intensity before treatment (T0) and at 1, 2, 3, 4 and 8 weeks after treatment; clinical manifestations; the fibromyalgia impact questionnaire (FIQ) before and at 4 and 8 weeks after; the levels of IL 1, 6 and 8 before and at 4 and 8 weeks after treatment.

RESULTS: Lower pain intensity was observed in the lidocaine group at T2, with no difference at the other time points. There was a reduction in pain intensity in both groups. The use of paracetamol and tramadol and plasma levels of IL-1, IL-6 and IL-8 did not differ between the groups. Clinical manifestations and side effects did not differ between groups.

CONCLUSIONS: The combination of 240 mg of intravenous lidocaine (once a week for 4 weeks) with 25 mg of amitriptyline for 8 weeks had no meaningful impact in fibromyalgia patients.