Tizanidine is used to help relax certain muscles in your body. It relieves spasms, cramping, and tightness of the muscles caused by medical problems, such as multiple sclerosis or certain injuries to the spine. Tizanidine does not cure these problems, but it may allow other treatment, such as physical therapy, to be more helpful in improving your condition. Tizanidine acts on the central nervous system (CNS) to produce its muscle relaxant effects. Its actions on the CNS may also cause some of the medicine's side effects. This medicine is available only with your doctor's prescription.