Baclofen for spinal muscular atrophy

Last updated Feb. 5, 2025, by Andrea Lobo, PhD
Fact-checked by Jose Lopes, PhD

What is baclofen for SMA?

Baclofen is a muscle relaxant approved by the U.S. Food and Drug Administration (FDA) for the treatment of muscle spasticity — when muscles are abnormally stiff — and associated pain and rigidity in people with multiple sclerosis, spinal cord injury, or other spinal cord diseases.

It may also be used off-label to help manage muscle spasms and spasticity in people with spinal muscular atrophy (SMA).

Baclofen was originally developed by Ciba-Geigy, now part of Novartis. It is sold under the brand names Lyvispah and Gablofen, among others. Generics are available.

Therapy snapshot

How does baclofen work?

SMA is a rare disease mainly caused by mutations in the SMN1 gene, which provides instructions to produce the survival motor neuron protein, known as SMN. The loss of this protein leads to the dysfunction and loss of motor neurons, the nerve cells that control voluntary movement, leading to muscle weakness and wasting.

In normal nerve signaling, a message sent from the brain travels along nerve cells to muscle cells, resulting in muscle movement. SMA, however, may impair nerve signaling, leading to spasticity and painful muscle spasms.

Baclofen has a similar structure to gamma-aminobutyric acid, or GABA, a signaling molecule nerve cells use to communicate. GABA works by decreasing the likelihood of these cells receiving, creating, or sending nerve signals. Baclofen binds to the GABA-B receptor to treat spasticity and muscle spasms.

How is baclofen administered?

Baclofen may be given orally as tablets, as oral suspensions, or as granules:

• Oral tablets and granules are available at doses ranging from 5 mg to 20 mg.
• An oral solution is available at 25 mg/5ml and other strengths.

Treatment with oral formulations is usually started with a small dose, typically 5 mg three times a day, that can be increased every three days based on clinical response and tolerability. The maximum recommended daily dose is 80 mg: 20 mg four times a day.

Baclofen can also be given by intrathecal administration, directly into the spinal canal, via a single injection or using an implantable and programmable pump.

In general, low oral doses — within the dosing range — may be needed in elderly patients and those with kidney problems.

Common side effects of baclofen

The most common side effects of baclofen reported in people treated for spasticity, but not due to SMA specifically, include:

• sleepiness
• nausea
• drowsiness
• dizziness
• constipation
• low muscle tone
• weakness
• headache
• low blood pressure
• chills
• high white blood cell count, known as leukocytosis
• agitation
• convulsions (when muscles contract and relax quickly, causing uncontrolled shaking)
• urinary retention (when the bladder doesn’t empty completely or at all).

Adverse reactions associated with abrupt withdrawal

Stopping baclofen abruptly may result in adverse reactions, including hallucinations (sensing things such as visions, sounds, or smells that seem real but are not), seizures, fever, altered mental status, exaggerated spasticity, and muscle rigidity. In rare cases, it may lead to muscle breakdown, failure of multiple organ systems, and death. Therefore, baclofen dosage should be reduced slowly.

The FDA requires a boxed warning for intrathecal baclofen to highlight the risk of abrupt treatment withdrawal. In the case of intrathecal delivery, preventing abrupt discontinuation requires careful attention to the infusion system, refill procedures, and pump alarms. Patients and caregivers should be aware of the importance of keeping scheduled refill visits and should know the early symptoms of baclofen withdrawal.

Withdrawal symptoms in newborns

Newborns of mothers treated with baclofen throughout pregnancy have shown symptoms such as increased muscle tone, tremor, and seizures, occurring hours to days after delivery. For that reason, and if the benefits outweigh the perceived risks, the dosage of baclofen should be reduced until treatment is stopped altogether before delivery.

Drowsiness and sedation

Baclofen may cause drowsiness and sedation. Patients should not drive or operate any other machinery that requires being alert until they know how baclofen affects them.

Exacerbation of psychotic disorders, schizophrenia, or confusional states

Baclofen should be used with caution in people with psychotic disorders (severe mental disorders that cause abnormal thinking and perceptions), schizophrenia (a serious mental illness that affects how a person thinks, feels, and behaves), or confusional states.

Epilepsy

Treatment with baclofen may interfere with seizure control.  Therefore, baclofen should be used with caution in patients with epilepsy.

Use in stroke patients

People who have had a stroke have shown poor tolerability to baclofen and little benefit from this drug. For these reasons, baclofen should be used with caution in this patient population.

Posture and balance effects

Baclofen should also be used with caution in people whose spasticity helps sustain upright posture and balance, or to obtain increased function.

Use in patients with history of autonomic dysreflexia

Caution should be taken when using baclofen in patients with autonomic dysreflexia, which is an overaction of the autonomic nervous system that causes a sudden and severe rise in blood pressure, in addition to other symptoms.

Ovarian cysts

Some women with multiple sclerosis developed ovarian cysts after being treated with baclofen for up to one year. In most cases, these cysts disappeared spontaneously with treatment.

Risks associated with intrathecal administration

Delivery of baclofen directly to the spinal canal is associated with an increased risk of overdose during pump refills, which should be done by fully trained personnel. Overdose symptoms include drowsiness, dizziness, somnolence, or daytime sleepiness, respiratory depression, seizures, low muscle tone, and loss of consciousness.

Additionally, patients should be infection-free to reduce the risk of complications following pump implantation. In some cases, intrathecal mass formation at the place of implantation may occur, which may reduce treatment efficacy, and cause pain and neurological symptoms.

Pediatric use

The safety and efficacy of oral baclofen formulations have not been established for children younger than age 12. For intrathecal formulations, children should have sufficient body mass to accommodate the implantable pump for continuous infusion. The safety and efficacy of this administration route have not been evaluated in children younger than 4 years old.

Use in pregnancy and breastfeeding

The use of baclofen during pregnancy can result in withdrawal symptoms in the newborn, including increased muscle tone, tremors, and seizures. Therefore, the benefits of the use of baclofen for the mother must be weighed against the potential risks for the fetus.

At therapeutic oral doses, baclofen can pass into breast milk, however, it is not known whether detectable levels are present in the human milk of mothers receiving intrathecal baclofen. Therefore, the health benefits of breastfeeding should be considered along with the mother’s need for baclofen and the potential adverse effects for the nursing infant before treatment is prescribed.

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