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Anticonvulsant medication Gabapentin effective for fibromyalgia pain
June 14, 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 percent) and men with the condition, Lesley M. Arnold, M.D.,
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. M.D., Ph.D., remarked that While
gabapentin does not have Food and Drug Administration 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 subunit 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.
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