Baclofen is a centrally acting muscle relaxant commonly prescribed for spasticity in patients with multiple sclerosis. Baclofen has not been linked to rare instances of mild, self-limited, clinically apparent liver injury.


Baclofen (bak' loe fen) is a gamma-amino butyric acid (GABA) derivative that acts as an agonist of the GABA B receptor, thereby activating potassium channels and reducing calcium conductance leading to hypotonia and muscle relaxation. Baclofen acts primarily at the level of the spinal cord, inhibiting synaptic reflexes. Baclofen reduces the number and severity of muscle spasms and relieves pain, clonus and muscle rigidity due to spasticity. Baclofen is indicated primarily for treatment of spasticity from spinal cord injuries and multiple sclerosis. It has been used off label as adjunctive therapy to help with alcohol abstinence and withdrawal. Baclofen was approved for use in the United States in 1977 and is widely used with several million prescriptions filled yearly. Baclofen is available in various generic forms as well as under the brand names of Lioresal and Remular in tablets of 10 or 20 mg and in formulations for intrathecal injections of 0.5 mg/mL. The recommended adult dose for spasticity is 10 to 20 mg orally three to four times daily. The dose should be increased and tapered gradually. The most common side effects of baclofen are nausea, drowsiness, confusion, dizziness and fatigue.


Limited data are available on the potential hepatotoxicity of baclofen. Among the many clinical trials evaluating the safety and efficacy of baclofen, none mentioned hepatic toxicity or rates of serum ALT elevations occurring during chronic therapy. The product insert starts that 5% of treated patients develop mild serum aminotransferase elevations, but little documentation is available on the significance, severity or duration of these abnormalities. A single case of mild and self-limited hepatitis attirbuted to baclofen has been published. The latency to onset was 3 months, the pattern of injury was hepatocellular, and recovery was rapid and complete, all laboratory tests being normal within a few weeks of stopping.

Likelihood score: D (Possible, rare cause of clinically apparent liver injury).

Mechanism of Injury

The apparent absence of significant hepatotoxicity from baclofen may be due to its minimal hepatic metabolism (~15%) and rapid urinary excretion.

Outcome and Management

The minor ALT elevations associated with chronic baclofen use are usually asymptomatic and transient. Any elevation of greater than 10 times the upper limit of normal or persistence of abnormalities greater than 5 times the upper limit of normal should lead to discontinuation. Cases of clinically apparent liver injury have been self-limited in course and outcome and there have been no reports of acute liver failure, chronic hepatitis or vanishing bile duct syndrome associated with its use. There is no reason to suspect cross sensitivity to liver injury among the various muscle relaxants.

Drug Class: Muscle Relaxants



Baclofen – Generic, Lioresal®


Autonomic Agents: Muscle Relaxants, Central


Product labeling at DailyMed, National Library of Medicine, NIH



References updated: 30 January 2017

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