muscle spasm
"I have severe sciatica caused by long distance driving.  I also have chronic insomnia.  I take 12 mg of tizanidine before I go to bed and go right to sleep.  If you are prescribed this medicine, just be warned it is like an anesthetic.  One minute you will be awake, the next you will be asleep.  I don't know how you can take it during the day.  Do not take it if you are going to drive.  Also, it is addictive, at least at the level that I take it.  I get the shakes around 5 PM.  But as far as benefit/harm is concerned, I think it is very good for what it does."