akathisia

literally, inability to remain motionless. a side effect of certain psychiatric drugs that can be a mild sense of disquiet or anxiety (which may be easily overlooked) to a total inability to sit still, accompanied by overwhelming anxiety, malaise, and severe dysphoria (manifesting as an almost indescribable sense of terror and doom). – wikipedia
often accompanied by dyskinesia, or tremor.

contrary to the other definition, it is treatable.
i had akathisia bad for a little while, it totally sucks. but it was all a matter of adjusting to my meds and working through the pain. distract yourself, supplements such as vitamin b6 and vitamin e are effective as are pharmaceuticals including benzodiazapines and the antihistamine cyproheptadine. talk to your psychiatrist if you get it, the solution could be as simple as lowering your dose or adding treatment.
1 more definition
1. a condition that is often times caused by neuroleptic drugs with symptoms including agitation, intense restlessness and a kind of detached physical pain that can be torturous.

2. a h-ll which is rarely visited and rarely escaped.
he was finally diagnosed with akathisia. explaining the illness to a man next to me i simply said, “another life destroyed in an unknown land.”

i walked to nowhere, never looking back.