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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 9 of 9. This is the beginning of the thread.
Posted by Deneb on December 1, 2005, at 14:26:13
How come Wellbutrin and Risperdal don't cancel each other out? Wellbutrin increases dopamine. Doesn't Risperdal decrease dopamine? My p-doc told me that Risperdal's actions are a lot more complicated. Can someone explain this to me? I'm guessing different types of dopamine receptors are involved in different parts of the brain. Am I right or wrong?
Deneb
Posted by linkadge on December 1, 2005, at 15:57:11
In reply to How come Wellbutrin and Risperdal don't cancel, posted by Deneb on December 1, 2005, at 14:26:13
Yes it is more complicated. The newer atypical antipschotics have a higher antagonist affinity for the serotonin receptors than they do for the dopamine receptors.
Risperdal blocks the serotonin 5-ht2a receptor much more potently then it does the d2 receptor.
As well, antipsychotics don't block all dopamine receptors, so if you take a dopamine enhancing drug, there still will be a net effect at certain dopamine receptors.
Another consideration is that Wellbutrin may have a stronger effect on noradrenaline than it does on dopamine.
Linkadge
Posted by Phillipa on December 1, 2005, at 23:12:52
In reply to Re: How come Wellbutrin and Risperdal don't cancel, posted by linkadge on December 1, 2005, at 15:57:11
Deneb Alex is looking for you on Social. Fondly, Phillipa
Posted by Larry Hoover on December 1, 2005, at 23:20:41
In reply to How come Wellbutrin and Risperdal don't cancel, posted by Deneb on December 1, 2005, at 14:26:13
> How come Wellbutrin and Risperdal don't cancel each other out? Wellbutrin increases dopamine. Doesn't Risperdal decrease dopamine? My p-doc told me that Risperdal's actions are a lot more complicated. Can someone explain this to me? I'm guessing different types of dopamine receptors are involved in different parts of the brain. Am I right or wrong?
>
> DenebOh yes, you are right. It is very complicated.
Are you up for beginning to learn just how complicated? I know you're bright, and with your chemistry background, you should grasp a lot of this stuff.
Go to: http://kidb.cwru.edu/pdsp.php
Wait a second for the page to load, and then enter either of bupropion or risperidone in the box on the left titled "Test Ligand". Don't worry about the other boxes, just now. Submit query.
That will bring up lists of the various receptors and transporters affected by the drugs in question. Ki is loosely the drug's affinity for that receptor type, with the lower concentration value indicating higher affinity (i.e. 50% occupancy at lower ambient concentration).
I hope you are boggled, perhaps slightly overwhelmed. And this table does not show antagonism vs. agonism, and all that. Hotlinks to the articles in Pubmed (right column) may give you that info, but you usually have to go to the full-text. And then there's brain region, as you so correctly consider. And then there is the issue of genetic differences (polymorphisms).
Pharmacological treatment is an art.
Lar
Posted by med_empowered on December 1, 2005, at 23:51:51
In reply to Re: How come Wellbutrin and Risperdal don't cancel » Deneb, posted by Larry Hoover on December 1, 2005, at 23:20:41
I don't know either, really...but it kind of makes sense. When you combine Zyprexa and Prozac, for instance, the combo increases dopamine, norepinephrine, and serotonin levels. Usually, antipsychotics decrease most (or all) of those neurotransmitters, and antidepressants only moderately increase levels of one or two. Also, if you read some old studies, you'll find that extremely low-dose *old* antipsychotics seem to do the same thing. This one study I read gave normal subjects .5mgs Haldol (very, very small dose)...their reaction times actually went *up*, not down, which is a reaction more common to a stimulant, not an antipsychotic.
Posted by linkadge on December 2, 2005, at 10:53:02
In reply to Re: How come Wellbutrin and Risperdal don't cancel, posted by med_empowered on December 1, 2005, at 23:51:51
The 5-ht2 system asserts an inhibitory control over dopamine release in certain areas of the brain.
Blocking the 5-ht2a receptor releases dopamine and norepinphrine in the frontal cortex. This is supposedly why the atypicals are better for certain negitive symptoms.
Linkadge
Posted by Deneb on December 2, 2005, at 14:23:52
In reply to Re: How come Wellbutrin and Risperdal don't cancel » Deneb, posted by Larry Hoover on December 1, 2005, at 23:20:41
Thanks for the cool website Lar!
There's a lot of really cool stuff on the net. I remember this other site where you can enter in a gene and get comparisons with different animals. I don't remember that website right now, but it's really cool too.
Deneb
Posted by Larry Hoover on December 3, 2005, at 13:55:59
In reply to Re: How come Wellbutrin and Risperdal don't cancel, posted by Deneb on December 2, 2005, at 14:23:52
> Thanks for the cool website Lar!
You're welcome.
> There's a lot of really cool stuff on the net. I remember this other site where you can enter in a gene and get comparisons with different animals. I don't remember that website right now, but it's really cool too.
>
> DenebOh! Oh! You tease! Please find it again, okay?
http://compbio.mcs.anl.gov/puma2/cgi-bin/index.cgi
http://www.genome.ad.jp/kegg/
http://www.brenda.uni-koeln.de/Lar
P.S. Buttertart!
Posted by Deneb on December 3, 2005, at 14:46:11
In reply to Re: How come Wellbutrin and Risperdal don't cancel » Deneb, posted by Larry Hoover on December 3, 2005, at 13:55:59
The website I couldn't find was right under my nose! It's part of the NCBI site. I'd forgotten the tool was called BLAST (Basic Local Alignment Search Tool).
www.ncbi.nlm.nih.gov/BLAST
You can search for similarities between sequences of different organisms.
This is the end of the thread.
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