Baclofen is approved by the U.S. Food and Drug Administration to treat muscle spasticity (uncontrolled muscle contraction) in people with multiple sclerosis (MS), but can also be used to treat muscle spasticity in those with spinal muscular atrophy (SMA).
What is spasticity?
SMA is a rare disease caused by the loss of nerve cells that control the movement of muscles. The loss of these nerve cells causes muscle weakness and atrophy and can also lead to muscle spasms or cramps, which can be painful.
In normal nerve signaling, a message is sent from the brain and travels along nerve cells to muscle cells. The muscles receive this message and move. In conditions like SMA, nerve signaling can be impaired and become overactive, leading to spasticity.
How baclofen works
Baclofen has a chemical structure very similar to an inhibitory neurotransmitter called gamma-aminobutyric acid (GABA), which reduces the excitability of nerve cells. Although its exact mechanism of action is not known, baclofen is thought to bind to and activate the same receptors on which GABA acts. In this way, baclofen increases the effect of GABA in the brain and reduces the severity and incidence of muscle spasms.
Baclofen in clinical trials
Baclofen’s effects have not been tested in controlled clinical trials specifically in SMA patients. However, its effects have been tested in other conditions that can cause spasticity like MS.
For example, a double-blind, five-week, multicenter trial assessed the effect of baclofen in 106 MS patients who were randomly assigned to receive either the therapy or a placebo. The results, which were published in the Archives of Neurology, showed that baclofen was effective at reducing the symptoms of spasticity, including pain and muscle stiffness. The side effects of the treatment were generally mild and transient.
Baclofen can cause side effects such as confusion, drowsiness, dizziness, nausea, and muscle weakness.
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