Posted by munificentexegete on February 11, 2007, at 2:47:29
In reply to Re: akathisia -- kaleidoscope » munificentexegete, posted by yxibow on February 10, 2007, at 21:42:45
>> kaleidoscope, you seem to know a lot about akathisia and medicine in general... what causes akathisia in serotogenic drugs? from all accounts it seems to be identical to the akathisia from neuroleptics; i've read no accounts that distinguish it from any other version of akathisia. the only other substances that I can think of that causes akathisia are nerve toxins like vx or sarin, organophosphate poisoning, and pesticides and from memory these substances cause extensive damage to the cholinergic system resulting in the extreme symptoms of anxiety, cognitive impairment, insomnia, and movement urges?
> Well SSRIs downregulate dopamine which could cause a blockade similar to the dopamine blockade in neuroleptics.
I haven't got to the end of it yet, however, i came across diquat/paraquat poisoning (herbicide) which induces akathisia, and organophosphate (pesticide) poisoning which also induces akathisia. and these all seem to work by blocking acetylcholinesterase and increasing ACh activity. and of course phenothiazines are both an antipsychotic and a pesticide. so my intial thoughts were that akathisia was probably due to antiacetylcholinesterase action. that said there isn't as much research on vx or organophosphates, so the effect these agents have on other systems such as dopamine isn't well documented and they may well interact with dopamine as well, in fact I suspect they do.
NMS seems to be almost identical to the reaction described from high doses of nerve toxins like vx or sarin, where acetylcholinesterase is blocked by the nerve toxins resulting in an oversupply of ACh and continuous muscle contractions including loss of control of the breathing muscles. although i haven't seen a trial of pralidoxime for NMS.
if akathisia was related to antiacetylcholinesterase activity then atropine should provide instantaneous relief, and while this is true of NMS and dystonias, it is generally only seen as having a low impact and partly efficacious for akathisia. So I suspect another physiology for akathisia... it could well be a dopamine phenomenom.
poster:munificentexegete
thread:730582
URL: http://www.dr-bob.org/babble/20070207/msgs/731747.html