muscle spasm
"It worked to get rid of neck pain and muscle spasms , but even with half a dose, I am unable to function the next day. I would be a dangerous driver. I feel like my head is wobbly and could fall off any second. I will not take it again until or unless my neck pain is so bad i don't care if I do anything the next several days.  I gave it a 6 because it was effective according to the guideliines, but my first thought was a 3.  At least with neck pain I could function."