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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 5 of 5. This is the beginning of the thread.
Posted by JohnL on November 23, 2000, at 6:57:14
I have been searching everywhere for information on Risperdal and Zyprexa. It is well documented that Amisulpride blocks presynaptic D2 at low doses, and post synaptic at higher doses. I am trying to find similar information for Risperdal and Zyprexa.
All I can find talks about D2 occupancy or D2 binding, but no mention of presynaptic or postsynaptic. That to me seems like a hugely relevent topic, and I am amazed I can't find any mention of it anywhere. Does anyone know?
It seems apparent from discussions at this board that varying doses of these drugs have different effects. That implies there could be differences in presynaptic or postsynaptic binding depending on dose size. But I can't find any info on that topic. ???
It amazes me that so much more is known about a European drug (Amisulpride) which has relatively little funding compared to the heavyweight makers of Risperdal and Zyprexa researchers. Weird.
Anyway, can anyone share information on presynaptic and postsynaptic actions of Risperdal or Zyprexa at various doses? I sure can't find it anywhere.
Thanks,
John
Posted by R.Anne on November 24, 2000, at 20:51:15
In reply to Risperdal Zyprexa questions.Andrew,Cam,SLS,anyone, posted by JohnL on November 23, 2000, at 6:57:14
The only place I can recommend to look is at http://us.janssen.com under products. There are 9 pages on Adobe Acrobat format. I couldn't copy them. I don't know if the info. you are looking for is there or not, though, as the print is very small and you need to print it out to see it. Good luck.
Posted by anita on November 24, 2000, at 22:29:17
In reply to Risperdal Zyprexa questions.Andrew,Cam,SLS,anyone, posted by JohnL on November 23, 2000, at 6:57:14
Hi John,
You forgot to ask me! ;-) I have looked everywhere for this type of information and have come up with nothing. Personally, I do think that very low doses of these atypical antipsychotics do in fact have a paradoxical effect, i.e. raise D2 levels in the mesolimbic pathway, in some way, tho I don't know if they would also antagonise the 5HT2 receptor. See my posts under Q. for Risperidal users.
For me at least, my response to Risperdal .25mg/day is quite similar to the response I had with low-dose amisulpride. If amisulpride worked for you, I would give very low dose Risperdal or Zyprexa a try -- really.
anita
I have been searching everywhere for information on Risperdal and Zyprexa. It is well documented that Amisulpride blocks presynaptic D2 at low doses, and post synaptic at higher doses. I am trying to find similar information for Risperdal and Zyprexa.
>
> All I can find talks about D2 occupancy or D2 binding, but no mention of presynaptic or postsynaptic. That to me seems like a hugely relevent topic, and I am amazed I can't find any mention of it anywhere. Does anyone know?
>
> It seems apparent from discussions at this board that varying doses of these drugs have different effects. That implies there could be differences in presynaptic or postsynaptic binding depending on dose size. But I can't find any info on that topic. ???
>
> It amazes me that so much more is known about a European drug (Amisulpride) which has relatively little funding compared to the heavyweight makers of Risperdal and Zyprexa researchers. Weird.
>
> Anyway, can anyone share information on presynaptic and postsynaptic actions of Risperdal or Zyprexa at various doses? I sure can't find it anywhere.
> Thanks,
> John
Posted by SLS on November 25, 2000, at 8:39:49
In reply to Risperdal Zyprexa questions.Andrew,Cam,SLS,anyone, posted by JohnL on November 23, 2000, at 6:57:14
John,
You'll never know until you try. Sometimes you gotta' say the hell with theory. Perhaps you can start off by adding the lowest starting dosage of Risperdal or Zyprexa (0.25mg and 2.5mg respectively) while still maintaining the amisulpride. After five days to seven days, you can then discontinue the amisulpride and hope the new drug prevents relapse. Just a thought.
For the week that I took Risperdal, I expereienced a noticeable negative change in both the "resting-state" and degree of tumescence of my penis. It is very possible that this would dissipate within a few weeks. I had no such side effect from Zyprexa. On the contrary, the brief antidepressant response I gleaned at 2.5mg revitalized my appetite and performance.
I wish that I could provide you with a "longer"-term observation.
I have decided to switch from Zyprexa to Risperdal as of tonight. If you want, I'll keep you informed on how things go.
For you, I think Zyprexa makes the most sense to try first, especially since gaining weight is not an issue with you.
- Scott
Posted by SLS on November 25, 2000, at 9:20:28
In reply to Re: Risperdal Zyprexa questions.Andrew,Cam,SLS,anyone, posted by anita on November 24, 2000, at 22:29:17
Dear Anita,
How are things going with Risperdal? Is 0.25mg. giving you a robust, steady improvement?I have decided to begin Risperdal tonight. I only have 1.0mg. tablets, so I guess I'll have to cut them. I'd like to start off at no higher than 0.5mg.
Zyprexa seems to display a therapeutic window for me. When I began at 2.5mg., I began to respond, but not robustly. When I first raised the dosage to 5.0mg., I obtained a moderate improvement. It didn't last. In fact, I just didn't like the way I was beginning to feel. I felt like I was in a bit of a fog and lost some of my "core" vigilant self. Perhaps this would have dissipated given more time, but without a return of a hint of antidepressant effect, I thought it best to switch to Risperdal so as to go in to my doctor supplied with the information of a comparison of the two, which was the goal set at my last visit.
A year ago, I asked my old doctor if there was a therapeutic window for Zyprexa when used for depression. He just smiled and looked away. Coming from him, this smile was an affirmation of the likelihood of such. I met a young woman in his waiting room who had been taking Zyprexa as monotherapy. She said that it worked great for 5 or 6 days, whereupon the improvement began to wane.
Anita to JohnL:
> Hi John,
> You forgot to ask me! ;-) I have looked everywhere for this type of information and have come up with nothing. Personally, I do think that very low doses of these atypical antipsychotics do in fact have a paradoxical effect, i.e. raise D2 levels in the mesolimbic pathway, in some way, tho I don't know if they would also antagonise the 5HT2 receptor. See my posts under Q. for Risperidal users.
> For me at least, my response to Risperdal .25mg./day is quite similar to the response I had with low-dose amisulpride. If amisulpride worked for you, I would give very low dose Risperdal or Zyprexa a try -- really.
> I have been searching everywhere for information on Risperdal and Zyprexa. It is well documented that Amisulpride blocks presynaptic D2...
and D3
> ...at low doses, and post synaptic at higher doses. I am trying to find similar information for Risperdal and Zyprexa.
Me:Zyprexa, and to a lesser degree, Risperdal, have extremely low affinities to D2 receptors when compared to the typical neuroleptics. Presynaptic autoreceptors tend to be "stickier" to begin with. At low concentrations, I can imagine how the ratio of presynaptic to postsynaptic occupancy might be quite high. Perhaps this provides a mild functional pro-dopaminergic condition similar to sulpiride and amisulpride. This type of thing would occur selectively in the limbic system and prefronal cortical areas. Perhaps there is a synergism between low-dosage pro-dopaminergic low-affinity D2 antagonism and the pro-dopaminergic effects in these same structures secondary to high-affinity 5-HT2a antagonism.
Just another uneducated guess...
- Scott
This is the end of the thread.
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