What is the role of baclofen in the treatment of spasticity?

Updated: Mar 01, 2018
  • Author: Krupa Pandey, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Answer

Baclofen is a GABA agonist, and its primary site of action is the spinal cord, where it reduces the release of excitatory neurotransmitters and substance P by binding to the GABA-B receptor. Studies show that baclofen improves clonus, flexor spasm frequency, and joint range of motion, resulting in improved functional status.

Baclofen may be given orally or by intrathecal pump. An analysis by Rizzo et al of a database of 17,501 patients with multiple sclerosis found that the use of oral medication was proportional to the severity of spasticity, with 78% of patients who were severely affected using at least 1 drug and 46% using at least 2. [10] Baclofen was the most commonly used agent, followed by gabapentin, tizanidine, and diazepam. Comparison of 198 patients who used intrathecal baclofen (ITB) and 315 who used oral medications showed that those who used ITB had lower levels of spasticity, less leg stiffness, less pain, and fewer spasms.

The oral dose of baclofen used to treat spasticity ranges from 30-100 mg/day in divided amounts. Tolerance may develop, and the drug must be tapered slowly to prevent withdrawal effects. Withdrawal from baclofen can have clinical manifestations that include agitation, insomnia, confusion, delusions, hallucinations, seizures, visual changes, psychosis, dyskinesia, hyperthermia, and increased spasticity. [17, 18]

Baclofen must be used with care in patients with renal insufficiency, as its clearance is primarily renal. Adverse effects include sedation, ataxia, weakness, and fatigue. When used in combination with tizanidine or benzodiazepines, the patient should be monitored for unwanted depressant effects. [19]

Adverse effects of baclofen can be minimized by intrathecal infusion of the drug, because the concentration gradient favors higher levels at the spinal cord versus the brain. Intrathecal baclofen is approved in the United States for the treatment of spasticity of spinal or cerebral origin.

In children, intrathecal baclofen is particularly effective for the treatment of spasticity of the lower extremities in a selected group of patients who have responded favorably to a trial intrathecal dose. Complications of the procedure are relatively few and usually are limited to mechanical failures of the pump or the catheter. Adverse drug effects are usually temporary and can be managed by reducing the rate of infusion.


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