Baclofen USP For Compounding (API) (Rx)Baclofen USP active pharmaceutical ingredient (API) is a centrally acting muscle relaxant that is used to treat symptoms of spastic movement disorders, such as multiple sclerosis, spinal cord injury, or cerebral palsy. It is a derivative of gamma aminobutyric acid (GABA), a neurotransmitter in the brain that plays a role in regulating muscle tone. Baclofen works by binding to specific GABA receptors, reducing the activity of neurons that cause muscle