muscle spasm
"The pain in my lower back due to some extreme exercise moves reacted immediately to this medication.  The first sign of improvement was when I lifted myself out of bed first morning after starting: 800 mg 3x a day.  However, ended up in the hospital a couple of days later due to severe nausea and loss of consciousness.  May be a combination of things that were going on. Still on it after about two weeks, and I am experiencing nausea and loss of appetite, as well as sleepiness.  Physical therapy along with this is working well.  I am about to ask the doctor if I can only take as needed."