Analgesic and anti-hyperalgesic effects of muscle injections with lidocaine or saline in patients with fibromyalgia syndrome

Background Patients with musculoskeletal pain syndrome including fibromyalgia (FM) complain of chronic pain from deep tissues including muscles. Previous research suggests the relevance of impulse input from deep tissues for clinical FM pain. We hypothesized that blocking abnormal impulse input with intramuscular lidocaine would decrease primary and secondary hyperalgesia and FM patients’ clinical pain.