Baclofen is used orally in the management of spasticity and its sequelae secondary to severe chronic disorders such as multiple sclerosis and other types of spinal cord lesions. For the drug to be beneficial, patients must have presumably reversible spasticity where relief of spasticity will aid in restoring residual function. In these patients, baclofen decreases the number and severity of spasms (particularly flexor spasms); alleviates associated pain, clonus, and muscle rigidity; and improves mobility to a greater extent than does placebo. In patients with multiple sclerosis, the drug produces little improvement in residual muscle function, but patient comfort is improved when the painful spasms are reversible. In one uncontrolled study, less than one-third of multiple sclerosis patients with urinary retention caused by bladder spasm showed decrease in urinary retention.
In studies comparing doses of about 60 mg of baclofen daily to 30 mg of diazepam daily in patients with multiple sclerosis or spinal cord lesions, the drugs were equally effective in reducing the number and severity of muscle spasms; however, baclofen produced a lower incidence of sedation than did diazepam. There are no published studies comparing the efficacy of baclofen and dantrolene; baclofen may cause less severe adverse effects than does dantrolene. Some clinicians consider baclofen to be the treatment of choice for muscle spasm in patients with multiple sclerosis or spinal cord lesions and diazepam to be the drug of second choice. Either drug usually is preferable to intrathecal injection of sclerosing agents (e.g., phenol, dilute alcohol), rhizotomy, or chordotomy.
Baclofen crosses the blood-brain barrier in only small amounts following oral administration. It has been suggested that administration of the drug at the spinal cord level (i.e., intrathecally) would increase drug efficacy while decreasing the dosage required and possibly the toxicity profile in patients with spasticity of spinal cord origin. While baclofen may be effective at relatively high oral dosages in some patients with spasticity of spinal cord origin, many other patients, particularly those with severe spasticity, do not respond adequately to and/or do not tolerate such therapy. Therefore, intrathecal baclofen may be a suitable alternative to ablative surgical or chemical procedures in patients who do not tolerate or respond adequately to oral therapy with the drug. (
See Uses: Severe Spasticity.)
Baclofen usually is used intrathecally in the management of severe spasticity of spinal cord origin in patients who do not tolerate or respond adequately to oral therapy with the drug. Baclofen also is used intrathecally in the management of intractable spasticity secondary to severe chronic disorders such as multiple sclerosis and other types of spinal diseases such as spinal ischemia, spinal tumor, transverse myelitis, cervical spondylosis, and degenerative myelopathy. Baclofen is designated an orphan drug by the FDA for use in these conditions. The clinical goal of such therapy is to maintain muscle tone as close to normal as possible and to minimize the frequency and severity of spasms without inducing intolerable adverse effects. In controlled studies in patients with severe spasticity and spasms secondary to spinal cord injury or multiple sclerosis, single doses or 3-day continuous infusions of intrathecal baclofen were more effective than placebo in improving the Ashworth (rigidity) rating of spasticity and in reducing the frequency of spasms. During chronic intrathecal baclofen therapy, many patients experience improvement in activities associated with daily living, especially in self-care, transferring, bowel function, and urinary continence.
Baclofen also is used intrathecally in patients with spasticity of cerebral origin, including those with cerebral palsy and acquired brain injury. Baclofen injection is designated an orphan drug by the FDA for the management of spasticity in patients with cerebral palsy. The clinical goal of such therapy is to maintain muscle tone as close to normal as possible and to minimize the frequency and severity of spasms without inducing intolerable adverse effects or to titrate dosage of baclofen to the desired degree of muscle tone for optimal function. Results of one randomized, controlled, crossover study in patients with cerebral palsy indicate that intrathecal baclofen was more effective than placebo in reducing spasticity as measured by the Ashworth scale. In addition, results of a small (11 patients) controlled study in patients with brain injury indicate that intrathecal baclofen was more effective than placebo in reducing spasticity.
Patients with spasticity secondary to brain injury should wait at least one year after the injury before considering long-term intrathecal baclofen therapy.
Baclofen has been used orally to reduce choreiform movements in patients with Huntington's chorea, to reduce rigidity in patients with parkinsonian syndrome, and to reduce spasticity in patients with cerebral lesions, cerebral palsy, or rheumatic disorders; however, the drug has not been shown to produce a substantial degree of improvement in these patients. Oral baclofen also has been used to reduce spasticity in patients with cerebrovascular stroke; however, therapy with the drug generally did not provide substantial improvement and was poorly tolerated. The manufacturer states oral baclofen is not indicated for use in patients with rheumatic disorders; use of oral baclofen also is not recommended in patients with stroke, cerebral palsy, or Parkinson's disease.
Although in one study oral baclofen reportedly improved behavior in patients with schizophrenic disorder receiving other drugs concomitantly (e.g., phenothiazines), schizophrenic behavior worsened in other patients when baclofen was used alone. Preliminary data indicate that oral baclofen has beneficial effects in the treatment of trigeminal neuralgia and may be synergistic with carbamazepine and phenytoin.