Baclofen

What it is

Baclofen is a prescription muscle relaxant taken by mouth as tablets or liquid, or delivered by an implanted pump into the spinal fluid (intrathecal) for severe spasticity.

What the research says

It is approved to reduce spasticity from multiple sclerosis and spinal cord disease, though a Cochrane review found the trial evidence for anti-spasticity drugs in MS poorly documented. Off-label, a 2023 Cochrane review found it probably reduces relapse in alcohol use disorder and increases abstinent days, but does not reduce heavy drinking days. A large French cohort linked high doses to more hospitalisations and deaths. It commonly causes drowsiness, and in older people with kidney disease higher doses were linked to encephalopathy. Stopping abruptly can cause hallucinations and seizures, and stopping an intrathecal pump abruptly can be fatal.

Evidence grade: Limited evidence.

How it works

Drug class: GABA-B receptor agonist; centrally acting skeletal muscle relaxant

Baclofen acts on GABA-B receptors in the spinal cord, damping the nerve reflexes that make muscles over-contract in spasticity. It is mostly cleared unchanged by the kidneys, so it builds up when kidney function is poor. (Source 1)

Boxed warning

Abrupt discontinuation of intrathecal baclofen, regardless of the cause, has resulted in sequelae that include high fever, altered mental status, exaggerated rebound spasticity, and muscle rigidity, that in rare cases has advanced to rhabdomyolysis, multiple organ-system failure and death. Prevention of abrupt discontinuation of intrathecal baclofen requires careful attention to programming and monitoring of the infusion system, refill scheduling and procedures, and pump alarms. Patients and caregivers should be advised of the importance of keeping scheduled refill visits and should be educated on the early symptoms of baclofen withdrawal. Special attention should be given to patients at apparent risk (e.g., spinal cord injuries at T-6 or above, communication difficulties, history of withdrawal symptoms from oral or intrathecal baclofen).

(Source 2)

What it is used for

• A Cochrane review of 26 placebo-controlled and 13 comparative trials concluded the absolute and comparative efficacy and tolerability of anti-spasticity agents in MS is poorly documented. Evidence: limited. (Source 3)
• Approved for severe spasticity in adults and children 4 and older; we did not retrieve outcome trials for intrathecal delivery in this write-up. Evidence: unknown. (Source 4)
• The label states efficacy in these conditions has not been established. Evidence: not-supported. (Source 5)
• Cochrane 2023 (17 RCTs, 1,818 people): baclofen probably reduces relapse (RR 0.87) and increases abstinent days (by 9 percentage points), but does not reduce heavy drinking days. A French cohort of 165,334 patients found higher hospitalisation and death with baclofen, especially at high doses. Evidence: disputed. (Source 6)
• A 2023 systematic review of 26 trials reported improved reflux symptoms and test findings; side effects in under 5% of short-term and nearly 20% of long-term users. Evidence: limited. (Source 7)

Interactions

• Alcohol and other sedating drugs (CNS depressants) (label): Baclofen's sedating effects add to those of alcohol and other sedatives. (Source 8)

Stopping it

• Stopping oral baclofen suddenly has caused hallucinations and seizures; the label advises gradual reduction. (Source 9)
• Abrupt interruption of an intrathecal baclofen pump can cause high fever, confusion, rebound spasticity and, rarely, death; the boxed warning stresses keeping refill visits. This boxed warning is on intrathecal baclofen products such as Gablofen; the oral tablet label we read warns about abrupt withdrawal but does not carry a boxed warning. (Source 2)

What goes wrong

Drowsiness is the most common side effect of oral baclofen, followed by dizziness, weakness and fatigue. (Source 10)

• Official position, Certainty not rated.
• Size: Label summary of clinical experience; one controlled study of 175 patients.
• Who: People taking oral baclofen.
• How long: not stated.
• Result: Drowsiness 10 to 63% overall; in one controlled study of 175 patients, 63% on baclofen vs 36% on placebo. Dizziness 5 to 15%, weakness 5 to 15%, fatigue 2 to 4% (no placebo rates given for these)
• Funding: manufacturer label.

In one controlled study of 175 patients, transient drowsiness was observed in 63% of those receiving baclofen compared to 36% of those in the placebo group.

In older adults with chronic kidney disease newly prescribed baclofen, starting at 20 mg a day or more was associated with more hospital admissions for encephalopathy (confusion) within 30 days than starting below 20 mg a day. This is an association from observational data. (Source 11)

• Cohort study, Low certainty.
• Size: 15,942 older adults with CKD.
• Who: Adults 66 and older with chronic kidney disease newly prescribed baclofen, Ontario 2007-2018.
• How long: 30 days.
• Result: Encephalopathy 1.11% (108/9707) at 20 mg/day or more vs 0.42% (26/6235) below 20 mg/day; weighted RR 3.54 (2.24 to 5.59); weighted absolute risk difference 0.80% (0.55% to 1.04%). Both RR and RD compare higher with lower starting doses, not baclofen with no baclofen.
• Funding: not stated on the page we read.

Among older patients with CKD who were newly prescribed baclofen, the 30-day incidence of encephalopathy was increased among those prescribed higher doses compared with lower doses.

In French patients treated for alcohol use disorder, baclofen was associated with more hospitalisations and deaths than approved alcohol drugs, especially at high doses. (Source 12)

• Cohort study, Low certainty.
• Size: 165,334 patients (47,614 exposed to baclofen)
• Who: Adults 18-70 with alcohol use disorder and no serious comorbidity, France 2009-2015.
• How long: 2009-2015.
• Result: Compared with approved alcohol use disorder drugs: hospitalisation HR 1.13 (1.09-1.17); death HR 1.31 (1.08-1.60); at high doses (180 mg/day or more) hospitalisation HR 1.46 (1.28-1.65) and death HR 2.27 (1.27-4.07)
• Funding: French national health insurance / drug agency (independent)

This study raises concerns about the safety of baclofen for AUD, particularly at high doses, with higher risks of hospitalisation and mortality than approved drugs.

What the evidence supports

In alcohol use disorder, baclofen probably reduces the risk of relapse to any drinking compared with placebo. (Source 6)

• Systematic review, Moderate certainty.
• Size: 12 studies, 1,057 participants (17 RCTs, 1,818 in the review)
• Who: Adults with alcohol use disorder.
• How long: Trial durations varied.
• Result: RR 0.87 (95% CI 0.77 to 0.99)
• Funding: Cochrane review (independent)

Compared to placebo, moderate-certainty evidence found that baclofen probably decreases the risk to relapse (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.77 to 0.99; 12 studies, 1057 participants).

Baclofen increases the percentage of days without drinking. (Source 6)

• Systematic review, High certainty.
• Size: 16 studies, 1,273 participants.
• Who: Adults with alcohol use disorder.
• How long: Trial durations varied.
• Result: Mean difference 9.07 percentage points (3.30 to 14.85)
• Funding: Cochrane review (independent)

High-certainty evidence found that baclofen increases the percentage of days abstinent (mean difference (MD) 9.07, 95% CI 3.30 to 14.85; 16 studies, 1273 participants).

In reflux disease, baclofen improved symptoms and reflux test results across 26 trials, with more side effects in long-term use. (Source 7)

• Systematic review, Certainty not rated.
• Size: 26 papers.
• Who: Adults, children, reflux-related cough and hiatal hernia patients.
• How long: Short- and long-term.
• Result: Side effects under 5% short-term, nearly 20% long-term.
• Funding: not stated.

The results revealed that baclofen can significantly improve reflux symptoms and pH-monitoring and manometry findings to different degrees in all four mentioned categories; although its effect on pH-monitoring parameters seems less significant than the other parameters.

What the evidence does not support

Baclofen did not reduce heavy drinking days or drinks per drinking day compared with placebo. (Source 6)

• Systematic review, Moderate certainty.
• Size: 13 studies, 840 participants.
• Who: Adults with alcohol use disorder.
• How long: Trial durations varied.
• Result: SMD −0.18 (95% CI −0.48 to 0.11)
• Funding: Cochrane review (independent)

There was no difference between baclofen and placebo in the other primary outcomes: heavy drinking days (standardised mean difference (SMD) −0.18, 95% CI −0.48 to 0.11; 13 studies, 840 participants; moderate-certainty evidence); number of drinks per drinking days (MD −0.45, 95% CI −1.20 to 0.30; 9 studies, 392 participants; moderate-certainty evidence); number of participants with at least one adverse event (RR 1.05, 95% CI 0.99 to 1.11; 10 studies, 738 participants; high-certainty evidence); dropouts (RR 0.88, 95% CI 0.74 to 1.03; 17 studies, 1563 participants; high-certainty evidence); dropouts due to adverse events (RR 1.39, 95% CI 0.89 to 2.18; 16 studies, 1499 participants; high-certainty evidence).

For multiple sclerosis spasticity, the trials of baclofen and other anti-spasticity drugs are too poor to guide prescribing. (Source 3)

• Systematic review, Low certainty.
• Size: 26 placebo-controlled and 13 comparative studies.
• Who: People with multiple sclerosis.
• How long: Varied.
• Result: No pooled effect; efficacy poorly documented.
• Funding: Cochrane review (independent)

The absolute and comparative efficacy and tolerability of anti-spasticity agents in multiple sclerosis is poorly documented and no recommendations can be made to guide prescribing.

The label states baclofen has not been shown to work for spasticity from stroke, cerebral palsy or Parkinson's disease. (Source 5)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: People with stroke, cerebral palsy or Parkinson's disease.
• How long: not applicable.
• Result: Efficacy not established (label position, revised Aug 2019)
• Funding: manufacturer label.

The efficacy of baclofen in stroke, cerebral palsy, and Parkinson's disease has not been established and, therefore, it is not recommended for these conditions.

Where the research disagrees

Whether baclofen should be used for alcohol use disorder

• Cochrane review, Agabio et al. 2023, systematic review of 17 RCTs: Baclofen likely reduces the risk of relapse to any drinking and increases the percentage of abstinent days, mainly among detoxified participants. (Source 13)
• Chaignot et al., French national cohort 2018, cohort of 165,334 patients: This study raises concerns about the safety of baclofen for AUD, particularly at high doses, with higher risks of hospitalisation and mortality than approved drugs. (Source 12)

How much

• Reference intake: Dosing is set by the prescriber. The oral baclofen label (revised Aug 2019) is a position: it describes gradual titration for spasticity. (Source 14)
• Upper limit: The oral baclofen label (revised Aug 2019) states the total daily dose should not exceed 80 mg (20 mg four times daily). This is the label's position. (Source 14)
• Studied: In the French alcohol use disorder cohort, 'high doses' were defined as 180 mg/day or more, far above the label maximum; these were associated with higher death rates. (Source 12)

A common belief, and what the research shows

The belief: Baclofen is a harmless muscle relaxant that can simply be stopped.

What the research shows: The label warns "Hallucinations and seizures have occurred on abrupt withdrawal of baclofen." In older adults with kidney disease, higher starting doses were linked to more encephalopathy.

Questions and answers

What is it?

A prescription muscle relaxant used for spasticity, taken by mouth or delivered by an implanted spinal pump. (Source 4)

What does it do in the body?

It damps the spinal reflexes that make muscles over-contract. (Source 1)

Is it good or bad for you?

It is approved for spasticity, but trial evidence in MS is poor; off-label in alcohol use disorder it modestly reduces relapse. Drowsiness is common, and harms include confusion in kidney disease and dangerous withdrawal. (Source 13)

How do you get more of it?

Does not apply. Baclofen is prescription-only; the dose is set by the prescriber, with a label maximum of 80 mg a day for tablets. (Source 14)

If it is harmful, what reduces it?

The kidneys clear baclofen largely unchanged, so poor kidney function lets it build up. Stopping must be gradual, under the prescriber. (Source 9)

Why might someone be low in it or missing it?

Does not apply. Baclofen is a synthetic drug, not a nutrient or body substance. (Source 5)

We searched: Label and reviews read for this write-up; the question does not apply to a synthetic drug.

Which whole foods contain it or feed it?

No food contains baclofen. Alcohol adds to its sedating effect. (Source 8)

What happens if you do not have it?

For someone taking it, sudden absence is the danger: abrupt withdrawal can cause hallucinations and seizures, and pump interruption can be fatal. (Source 2)

How can you test for it?

No routine blood test for baclofen is described in the sources we read; effect and toxicity are judged clinically. (Source 5)

We searched: Label, Cochrane reviews and cohort studies read for this write-up.

References

1. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Clinical Pharmacology. 2019. Read the source
2. US FDA labeling (Gablofen), as posted on DailyMed. GABLOFEN (baclofen injection) for intrathecal use - Prescribing Information (revised 7/2025), Boxed Warning. 2025. Read the source
3. Cochrane Database of Systematic Reviews, CD001332. Anti-spasticity agents for multiple sclerosis (Shakespeare D, Boggild M, Young CA). 2003. DOI 10.1002/14651858.CD001332. Read the source
4. US FDA labeling (Gablofen), as posted on DailyMed. GABLOFEN (baclofen injection) for intrathecal use - Prescribing Information (revised 7/2025), Indications and Usage. 2025. Read the source
5. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Indications. 2019. Read the source
6. Cochrane Database of Systematic Reviews 2023, Issue 1, CD012557.pub3. Baclofen for alcohol use disorder (Agabio R et al.), abstract main results vs placebo. 2023. DOI 10.1002/14651858.CD012557.pub3. Read the source
7. Frontiers in Medicine. Baclofen as a therapeutic option for gastroesophageal reflux disease: A systematic review of clinical trials. 2023. DOI 10.3389/fmed.2023.997440. Read the source
8. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Precautions. 2019. Read the source
9. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Warnings. 2019. Read the source
10. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Adverse Reactions. 2019. Read the source
11. JAMA 2019;322(20):1987-1995 (abstract as shown on McMaster Experts page). Association of Baclofen With Encephalopathy in Patients With Chronic Kidney Disease (Muanda FT et al.), abstract results and conclusion. 2019. DOI 10.1001/jama.2019.17725. Read the source
12. Pharmacoepidemiology and Drug Safety. Risk of hospitalisation and death related to baclofen for alcohol use disorders: Comparison with nalmefene, acamprosate, and naltrexone in a cohort study of 165 334 patients between 2009 and 2015 in France (Chaignot C et al.). 2018. Read the source
13. Cochrane Database of Systematic Reviews 2023, Issue 1, CD012557.pub3. Baclofen for alcohol use disorder (Agabio R et al.), abstract authors' conclusions. 2023. DOI 10.1002/14651858.CD012557.pub3. Read the source
14. US FDA labeling, as reproduced by RxList. Baclofen tablets USP - Prescribing Information (revised Aug 2019), as reproduced by RxList, Dosage and Administration. 2019. Read the source