muscle spasm
"I went to the doctor this week for what I thought was a pinched nerve that caused shoulder pain.  She determined that it was muscle strain (trapezius) and prescribed 10mg to be taken twice daily as needed.  I took one in the afternoon on Thursday and another Wednesday morning.  I ended up sleeping the entire day (except for getting up to make lunch for the kids).  Later in the evening I started to feel very weak in my limbs (sort of like when you're getting over a really bad flu where you've been laid up in bed for days).  I also started to feel impaired - dizzy, lightheaded, just out of it. The next day I didn't have the limpness, but I still had the lightheadedness and my calves were achy - maybe from too much sleep."