Baclofen

Key facts

• Baclofen (tablets, oral liquid such as Fleqsuvy, and an implanted pump for severe cases) is a muscle relaxant that calms overactive nerve signals to ease spasticity.
• It is taken several times a day by mouth, usually starting at a low dose that is increased gradually; benefits on stiffness build over days to weeks.
• Never stop baclofen suddenly. Abrupt withdrawal can cause seizures, hallucinations, high fever and a dangerous rebound of muscle spasticity, so the dose must always be tapered down.
• Seek urgent care for confusion, hallucinations, a seizure, or muscle weakness severe enough to affect breathing.

What baclofen treats

Baclofen treats spasticity, the muscle stiffness and spasms caused by multiple sclerosis or spinal cord injury or disease, and it is also used for spasticity following a stroke in some cases. It does not treat ordinary muscle strain or tension headaches.

How baclofen works

Baclofen activates GABA-B receptors in the spinal cord. This dampens the overactive nerve signals responsible for excessive, involuntary muscle contraction, easing stiffness and reducing the frequency and severity of spasms.

Before you take it

• Use with caution if you have kidney disease, since baclofen is cleared by the kidneys and can build up to higher levels.
• Tell your prescriber about a history of seizures or psychiatric illness.
• Combining baclofen with alcohol, opioids, sleep aids or other sedating medicines increases drowsiness and the risk of slowed breathing.
• Older adults are more sensitive to confusion, drowsiness and falls.

Side effects

Common effects include drowsiness, dizziness, weakness, nausea, and dry mouth.

Stop and seek urgent medical care for any of these:

• Severe weakness or difficulty breathing.
• Hallucinations or confusion.
• A seizure.
• Signs of withdrawal, such as fever, worsening spasticity or seizures, if a dose is missed or stopped abruptly.

Safety essentials

• The withdrawal risk is absolute: never stop baclofen abruptly and never let a prescription lapse, especially with an implanted pump, where a sudden interruption is a medical emergency. Any dose reduction must be tapered under medical guidance.
• Reduce the dose in kidney impairment, and avoid combining baclofen with alcohol or other sedatives, which raises the risk of severe drowsiness and slowed breathing.
• Rise slowly from sitting or lying to reduce the risk of falls from dizziness or weakness.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.