(R)-Baclofen Hydrochloride, also known as STX 209 hydrochloride, is the pharmacologically active (R)-enantiomer of baclofen and a selective GABA-B receptor agonist. This specialty chemical is primarily used in research for treating spasticity associated with conditions such as multiple sclerosis, spinal cord injuries, and cerebral palsy. It reduces muscle stiffness and spasms by inhibiting signal transmission in the spinal cord. It is also explored in research for managing alcohol withdrawal symptoms and reducing cravings in alcohol use disorder, as well as improving social behavior and cognitive function in autism spectrum disorder and Fragile X syndrome. Studied administration routes include oral and intrathecal infusion, depending on the research context.