Drug Class and Mechanism: Baclofen is an oral medication that relaxes skeletal muscles, the muscles that move the skeleton (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 is a medicine used to treat the muscle spasms, cramping, and tightness that affect many people with multiple sclerosis, spinal cord conditions, or tardive dyskinesia. It relaxes muscles by acting on the brain and spinal cord.
Baclofen was approved by the FDA in November, 1977.
Preparations: Tablets: 10 and 20 mg. Intrathecal: 0.05 mg/ml, 10 mg/5ml, 10 mg/20 ml
Storage: Baclofen should be stored between 15°C (59°F) and 30°C (86°F).
Prescribed For: Baclofen is used for treating spasm of skeletal muscles that cause muscle clonus, rigidity, and pain due to multiple sclerosis.
Dosing: The usual starting dose of baclofen for adults is 5 mg given three times daily. Based on the response, the dose can be increased gradually every three days to a maximum of 80 mg/day in several doses.
Drug Interactions: 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 (e.g., Elavil, Sinequan) together may cause muscle weakness.
Use of baclofen and monoamine oxidase inhibitors (e.g. Nardil, 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.
Pregnancy: The use of baclofen by pregnant women has not been evaluated.
Nursing Mothers: 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.
Side Effects: Baclofen may cause 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.