June 11, 2007 -- New research supported by the National
Institutes of Health's National Institute of Arthritis and
Musculoskeletal and Skin Diseases (NIAMS) shows that the anticonvulsant
medication gabapentin, which is used for certain types of seizures, can
be an effective treatment for the pain and other symptoms associated
with the common, often hard-to-treat chronic pain disorder,
fibromyalgia.
In the NIAMS-sponsored, randomized, double-blind clinical trial of 150
women (90%) and men with the condition, Lesley M. Arnold, MD, director
of the Women's Health Research Program at the University of Cincinnati
College of Medicine, and her colleagues found that those taking
gabapentin at dosages of 1,200 to 2,400 mg daily for 12 weeks displayed
significantly less pain than those taking placebo. Patients taking
gabapentin also reported significantly better sleep and less fatigue.
For the majority of participants, the drug was well tolerated. The most
common side effects included dizziness and sedation, which were mild to
moderate in severity in most cases.
NIAMS Director Stephen I. Katz. MD, PhD, remarked that "While
gabapentin does not have FDA approval for fibromyalgia, I believe this
study offers additional insight to physicians considering the drug for
their fibromyalgia patients. Fibromyalgia is a debilitating condition
for which current treatments are only modestly effective, so a study
such as this is potentially good news for people with this common,
painful condition."
Fibromyalgia is a chronic disorder characterized by chronic, widespread
muscle pain and tenderness, and is frequently accompanied by fatigue,
insomnia, depression, and anxiety. It affects three million to six
million Americans, mostly women, and can be disabling.
The precise cause of fibromyalgia in not known, but research suggests
it is related to a problem with the central nervous system's processing
of pain. As with some other chronic pain conditions, people with
fibromyalgia often develop a heightened response to stimuli,
experiencing pain that would not cause problems in other people. Yet,
unlike many other pain syndromes, there is no physical evidence of
inflammation or central nervous system damage.
Although gabapentin has little, if any, effect on acute pain, it has
shown a robust effect on pain caused by a heightened response to
stimuli related to inflammation or nerve injury in animal models of
chronic pain syndromes. Researchers have suspected that it might have
the same effect in people with fibromyalgia. The new research,
published in the April 2007 edition of Arthritis & Rheumatism,
indicates the suspicions were correct.
Although the researchers cannot say with certainty how gabapentin helps
reduce pain, Dr. Arnold says one possible explanation involves the
binding of gabapentin to a specific sub-unit of voltage-gated calcium
channels on neurons. "This binding reduces calcium flow into the nerve
cell, which reduces the release of some signaling molecules involved in
pain processing," she says.
How gabapentin improves sleep and other symptoms is less clear, and
there are probably different mechanisms involved in fibromyalgia
symptoms. "Gabapentin improved sleep, which is an added benefit to
patients with fibromyalgia who often report unrefreshing or disrupted
sleep," Dr. Arnold says.
What is important is that people with fibromyalgia now have a potential
new treatment option for a condition with few effective treatments.
"Studies like this give clinicians evidence-based information to guide
their treatment of patients," says Dr. Arnold.
SOURCE: The National Institutes of Health
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