Posted by metric on May 6, 2009, at 16:12:12
In reply to Mirtazapine and RLS, posted by West on May 4, 2009, at 12:44:48
> A course of mirtazapine was stopped short recently due to intense restless legs on the first night. I had crawling sensations and had to keep turning my legs round every 20 seconds or so. Taking a lot of clonazepam eventually did the job but it was my worst drug reaction since seroquel (same thing basically).
> Since dopamine agonists are used to treat this problem, is this a biological pointer to 'low dopamine' or is this too simplistic a theory?
I think it's more complicated than that, since dopamine could be modulating other systems downstream. It could also be a matter of relative dominance of one system over another. For example, disruption of the cholinergic-dopaminergic balance is a key factor in movement disorders such as Parkinson's disease (which is why patients with Parkinson's disease are often given anticholinergic drugs).* However, it seems sufficient to reduce dopaminergic activity in certain areas of the brain.
> How common is this?
I don't know. Both mirtazapine (6-aza-mianserin) and its chemical cousin mianserin are known to induce RLS on occasion.
I had a similar experience when combining mirtazapine with duloxetine. I thought it was noradrenergically mediated, given the pharmacology of the two drugs. It went away after a few nights. How much mirtazapine did you take? Reducing the dose and then increasing it gradually might help.
BTW, RLS is sort of a misnomer as the motor impulses aren't necessarily restricted to the legs.
* You might find the following paper of interest:
Tzavara, E.T. et al. "M4 muscarinic receptors regulate the dynamics of cholinergic and dopaminergic neurotransmission: relevance to the pathophysiology and treatment of related central nervous system pathologies." FASEB J. 04-1575fje(2004).doi:10.1096/fj.04-1575fje
http://www.fasebj.org/cgi/content/abstract/04-1575fjev1I'd like to emphasize that I have no special knowledge of movement disorders.
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