(HealthDay)—For patients with fibromyalgia, use of intravenous lidocaine has no meaningful impact, according to a study published online June 16 in the International Journal of Rheumatic Diseases.

Ana Laura Albertoni Giraldes, M.D., from the Federal University of São Paulo in Brazil, and colleagues conducted a randomized trial involving with fibromyalgia. Participants were randomized to receive lidocaine in saline solution or saline solution once a week for four weeks. All patients received amitriptyline for eight weeks. Patients underwent pain assessment, completed the fibromyalgia impact questionnaire, and had levels of interleukins (IL) 1, 6, and 8 measured before and after treatment.

The researchers found that the lidocaine group had lower pain intensity at week two of treatment, but not at other time points assessed during eight weeks. Both groups experienced a reduction in intensity at eight weeks after the start of treatment. There was no difference between the groups in use of acetaminophen and tramadol, or in plasma levels of IL-1, -6, and -8. There was no difference between the groups in clinical manifestations or side effects.

"The combination of 240 mg of intravenous lidocaine (once a week for four weeks) with 25 mg of amitriptyline for eight weeks had no meaningful in fibromyalgia patients," the authors write.