Uses: Baclofen is used to treat muscle tightness and cramping (spasms) caused by certain conditions such as spinal cord injury/disease, cerebral palsy, and multiple sclerosis. It works by relaxing the muscles. Decreasing spasms helps reduce pain and stiffness, improves your ability to move around, and lets you do more of your daily activities. Baclofen injection is used in patients who do not respond to or cannot tolerate the side effects of baclofen taken by mouth.