Baclofen is an oral and injectable medication that relaxes skeletal muscles, the muscles that move the skeleton (and also called striated muscle). Chemically, baclofen is related to gamma-aminobutyric acid (GABA), a naturally occurring neurotransmitter in the brain. Neurotransmitters are chemicals that nerves use to communicate with one another. GABA released by some nerves causes the activity of other nerves to decrease. It is believed that baclofen, acting like GABA, blocks the activity of nerves within the part of the brain that controls the contraction and relaxation of skeletal muscle. Baclofen was approved by the FDA in November 1977.

Baclofen is used for treating spasm of skeletal muscles, muscle clonus, rigidity, and pain caused by disorders such as multiple sclerosis. It is also injected into the spinal cord (intrathecal) for management of severe spasticity.

Common side effects of baclofen are:

• drowsiness,
• weakness,
• dizziness,
• headache,
• seizures,
• nausea,
• vomiting,
• low blood pressure,
• constipation,
• confusion,
• respiratory depression,
• inability to sleep,
• and increased urinary frequency or urinary retention.

Abrupt discontinuation of oral baclofen may cause seizures and hallucinations. Abrupt discontinuation of intrathecal baclofen may result in:

• high fever,
• rebound spasticity,
• muscle rigidity, and
• rhabdomyolysis (muscle breakdown) that can progress to failure of several organs, including the kidney, and even death.

The usual starting dose of oral baclofen for treating spasticity in adults is 5 mg given three times daily. Based on the response, the dose can be increased by 5 mg every three days to a maximum of 80 mg/day in divided doses.

Use of baclofen with other drugs that also depress the function of nerves may lead to additional reduction in brain function.

In addition to the risk of depressing brain function, the use of baclofen and tricyclic antidepressants (for example, amitriptyline [Elavil, Endep], doxepin [Sinequan, Adapin]) together may cause muscle weakness.

Use of baclofen and monoamine oxidase inhibitors (for example, phenelzine [Nardil], tranylcypromine or [Parnate]) can result in greater depression of brain function as well as low blood pressure.

Because baclofen can increase blood sugar, doses of antidiabetic drugs may need to be adjusted when baclofen is begun.

The use of baclofen by pregnant women has not been evaluated.

Baclofen can be detected in the breast milk of mothers taking oral baclofen. No information is available on the presence of baclofen in the breast milk of mothers receiving baclofen intrathecally.

• Baclofen is available as Tablets: 10 and 20 mg. Intrathecal: 0.05 mg/ml, 0.5 mg/ml, 1 MG/ML, 2 mg/ml
• Baclofen should be stored between 15 C (59 F) and 30 C (86 F).
• Gablofen, Lioresal are the brand names available for baclofen in the US.
• Baclofen is available in generic form. You need a prescription to obtain this medication.