• Metabolism: ~ 15% of the dose is metabolized in the liver, primarily by deamination. 70-80% of the dose is excreted unchanged or as metabolites in urine and the remainder is excreted in feces. Oral Baclofen is readily absorbed from the gastrointestinal tract. After oral administration, baclofen appears in the blodd within half an our. It is fairly distributed in most organs and body tissues. After oral administration of baclofen, about 85% is excreted unchanged in the urine and feces and the remainder is oxidatively dearninated in the liver to produce beta-(p-chlorophenyl)-gamma-hydroxybutyric acid as a major metabolite. (L1322). Route of Elimination: In a study using radiolabeled baclofen, approximately 85% of the dose was excreted unchanged in the urine and feces. Baclofen is excreted primarily by the kidney as unchanged drug; 70 - 80% of a dose appears in the urine as unchanged drug. The remainder is excreted as unchanged drug in the feces or as metabolites in the urine and feces. Half Life: 2.5-4 hours
• Uses/Sources: For the alleviation of signs and symptoms of spasticity resulting from multiple sclerosis, particularly for the relief of flexor spasms and concomitant pain, clonus, and muscular rigidity.
• Health Effects: Health effects include hypertonia, hyperthermia, formal thought disorder, psychosis, mania, mood disturbances, restlessness, and behavioral disturbances, tachycardia, seizures, tremors, autonomic dysfunction, hyperpyrexia, extreme muscle rigidity resembling neuroleptic malignant syndrome and rebound spasticity (L1098).
• Symptoms: LD₅₀=45 mg/kg (male mice, IV); LD₅₀=78 mg/kg (male rat, IV)
• Treatment: Treatment may involve "pumping" the stomach, inducing vomiting, administering an antidote, and providing supportive care. (L1099)
• Route of Exposure: Inhalation (L1104); ingestion (L1104); eye contact (L1104); dermal (L1104) Rapidly and almost completely absorbed from the GI tract.

• Carcinogenicity: No indication of carcinogenicity to humans (not listed by IARC).
• Toxicity: LD50: 45 mg/kg (Intravenous, Mouse) (A308) LD50: 78 mg/kg (Intravenous, Rat) (A308)

Baclofen is a direct agonist at GABAB receptors. The precise mechanism of action of Baclofen is not fully known. It is capable of inhibiting both monosynaptic and polysynaptic reflexes at the spinal level, possibly by hyperpolarization of afferent terminals, although actions at supraspinal sites may also occur and contribute to its clinical effect.