By Mary Elizabeth Dallas
People with fibromyalgia complain of chronic pain throughout their body as well as an increased sensitivity to pain. Doctors often have trouble treating this pain because it's unclear what causes it, the study authors noted.
In the new study, injecting lidocaine into peripheral tissues -- such as the muscles in the shoulders or buttocks -- effectively reduced pain sensitivity, the researchers found.
"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," study lead author Dr. Roland Staud, a professor of medicine at the University of Florida College of Medicine, said in a university news release.
"Over-the-counter medications and [narcotic] prescriptions such as opiates aren't really effective for controlling chronic pain conditions," he added. But with the new therapy, "we are able to explain the pain of chronic patients better and manage it better," Staud said. "We are making progress but it will take time."
The study involved 62 women with fibromyalgia. Each woman received four injections: two in certain muscles in their shoulders and two more in their buttocks. Some of the women received lidocaine injections, while a "control group" received saline injections.
Right before the injections were given and 30 minutes afterwards, the women received mild pain stimulations delivered through mechanical means or through heat.
Compared to "dummy" saline injections, the lidocaine significantly eased the women's sensitivity to pain, according to the study published recently in the European Journal of Pain.
The researchers noted, however, that both lidocaine and the placebo resulted in a 38 percent reduction in pain at or near the point of injury.
But chronic pain affects the body differently than a specific injury, like a broken leg, the study authors pointed out. Chronic pain, they explained, actually alters nerve function along the spinal cord.
"The best way to treat chronic pain conditions is . . . [by] looking at emotional, sensory and tissue damage," Michael Robinson, director of the University of Florida Center for Pain Research and Behavioral Health, said in a university news release. "We know there are central and peripheral and social and behavioral components to someone saying, 'Ow, it hurts.'"
Cancer survivors who experience pain, for example, may associate it with their disease and fears about their prognosis -- even if it's been treated and in remission.
"That sensation may well feel more painful than if they just thought it was a tweaked muscle," Robinson explained.
Two experts in fibromyalgia were unsure about the significance of the findings, however.
"There was no significant difference between the pain reduction in the placebo versus the treatment group -- this signifies that it does not matter what the injection product is, but the act of injection itself might be the cause of pain reduction," said Dr. Waseem Mir, a rheumatologist at Lenox Hill Hospital in New York City.
"One can then argue that the pain reduction was placebo," he said. "To examine the placebo point, another arm in the experiment might need to be introduced where patients are not getting injected but taking a placebo pill."
Dr. Houman Danesh is director of integrative pain management at Mount Sinai Hospital in New York City. He said that "fibromyalgia is a complex disorder where patients are more sensitive to pain. It is mainly diagnosed by a rheumatologist by touching 18 diagnostic pressure points, and if 11 of them are sensitive, then the diagnosis is made," he explained.
"This study offers insight as to a potential contributor to fibromyalgia and a possible treatment," Danesh said. "It is interesting to note that the points which were used were acupuncture points, therefore suggesting acupuncture as a possible treatment to help patients with fibromyalgia."