Patients diagnosed with fibromyalgia complain of chronic pain throughout their bodies, but often doctors have difficulty detecting what causes the pain, and therefore, how to treat it.

These patients also complain of hyperalgesia, or increased sensitivity to pain. A University of Florida study has found that injections of the painkiller lidocaine in peripheral tissues such as muscles in the shoulders or buttocks reduced hyperalgesia, bringing researchers one step closer to understanding how chronic pain works within these patients.

The study, published in the July issue of the European Journal of Pain, was conducted by Dr. Roland Staud, a professor of medicine in the UF College of Medicine’s department of medicine, and Dr. Michael Robinson, a professor in the department of clinical and health psychology in the UF College of Public Health and Health Professions

“We hypothesized that if pain comes from the peripheral tissues, and we can take this pain away by injecting local anesthetics, then this would be indirect proof of the importance of peripheral tissues for the clinical pain of these individuals,” Dr. Staud said.

Sixty-two women diagnosed with fibromyalgia were involved in the study. Each woman received two injections in the trapezius muscles of the shoulders and the gluteal muscles of the buttocks, for a total of four injections per patient. Although the lidocaine injections significantly reduced hyperalgesia, the placebo injections did not. The study also found that the lidocaine and saline placebo injections both resulted in a 38 percent reduction in patients’ clinical pain, or the pain a person feels at the point of injury as well as pain radiating throughout the area near the injury. There was no statistical difference between the painkiller and the saline placebo.

Treatment of chronic pain is difficult because doctors often cannot detect evidence of injury at the site where patients experience pain, Dr. Staud said. But chronic pain affects the body differently than, for example, a single incident such as a leg break. It actually changes nerve function along patients’ spinal cords, said Dr. Robinson, the director of the UF Center for Pain Research and Behavioral Health.

He said hyperalgesia is a phenomenon in which the nervous system becomes sensitized to stimulation, amplifying the intensity perceived by the patient. Knowing what kind of treatment is successful in treating this sensitivity could bring researchers closer to providing relief to patients — combating their hyperalgesia and curbing chronic pain.

“The best way to treat chronic pain conditions is multidisciplinary and multimodal, looking at emotional, sensory, and tissue damage. We know there are central and peripheral and social and behavioral components to someone saying, ‘Ow, it hurts,” Dr. Robinson said.

Read more: https://ufhealth.org/news/2014/painkiller-reduces-hypersensitivity-pain-patients-fibromyalgia