How tizanidine works
SMA is an inherited disorder associated with the progressive loss of motor neurons, or nerve cells, that control muscles. Spasticity, a sudden increase in muscle tone or involuntary muscle contraction, is one of several common symptoms in SMA. Spasticity can also include muscle twitches.
Muscles contract in response to signals transmitted from motor neurons in the brain and spinal cord. SMA can cause motor neurons involved in the stretch reflex to be hyperexcitable, or more likely to spontaneously send a signal, resulting in muscles suddenly tensing.
Tizanidine is a type of skeletal muscle relaxer that works by preventing the transmission of signals in some motor neurons. It is one of several central alpha 2 adrenoceptor agonists. These work by activating receptors in the nervous system that inhibit signals from being sent by the motor neurons. By reducing the signals being sent, tizanidine allows the muscles to relax. This should ease spasticity.
Tizanidine in clinical trials
Tizanidine has not been specifically tested in clinical trials for SMA, but it has been tested and approved as a treatment for spasticity due to other causes. For example, it has been investigated in clinical trials to treat spasticity in multiple sclerosis (MS), cerebral palsy, spinal cord injury, or following a stroke.
A 2008 review of tizanidine use for spasticity, published in the scientific journal Current Medical Research and Opinion, discussed 53 articles that demonstrated tizanidine’s efficacy in patients with MS, stroke, or a spinal cord injury. Overall, the literature suggests that tizanidine is effective at relieving spasticity, and may be more tolerable compared to other muscle relaxants such as baclofen or diazepam.
Common side effects of tizanidine are dizziness, fatigue, weakness, anxiety or depression, vomiting, constipation, diarrhea, stomach pain, heartburn, tingling sensations in the limbs or extremities, dry mouth, increased muscle spasms, back pain, rashes, or sweating. In a few rare cases, tizanidine has been linked to liver damage.
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