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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 12 of 12. This is the beginning of the thread.
Posted by linkadge on July 31, 2010, at 23:25:45
Ok, my question is this:
When you ingest citalopram, are there 3 drugs in action (citalopram, r-citalopram, s-citalopram) in action or just two (r-citalopram, s-citalopram)?
Thx,
Linkadge
Posted by Deneb on July 31, 2010, at 23:25:45
In reply to Stereochemistry question (re: citalopram), posted by linkadge on July 28, 2010, at 19:47:21
It's just the two stereoisomers, there is no "just" citalopram. It's like having a left handed citalopram and a right handed citalopram, there is no molecule without handedness if there is handedness.
Posted by Deneb on July 31, 2010, at 23:25:46
In reply to Re: Stereochemistry question (re: citalopram) » linkadge, posted by Deneb on July 28, 2010, at 20:42:12
The R and S entantimers are mirror images of one another. Our bodies enzymes are chiral (have handedness) and that is why it matters whether or not a drug is chiral. I forget which one it is that out bodies recognize.
Posted by linkadge on July 31, 2010, at 23:25:46
In reply to Re: Stereochemistry question (re: citalopram), posted by Deneb on July 28, 2010, at 20:47:32
Thanks Deneb, so does the drug separate into two seperate molecules when it enters the body?
Linkadge
Posted by Deneb on July 31, 2010, at 23:25:46
In reply to Re: Stereochemistry question (re: citalopram) » Deneb, posted by linkadge on July 28, 2010, at 20:51:17
No, the drug is already two different molecules before it enters the body.
The way Celexa is synthesized results in a mixture of both enantiomers. In Lexapro, chemists have figured out a way to make just the biologically active enantiomer.
Posted by Phillipa on July 31, 2010, at 23:25:46
In reply to Re: Stereochemistry question (re: citalopram) » linkadge, posted by Deneb on July 28, 2010, at 23:02:54
Deneb seriously you should be a chemist with a drug company. You understand so well. Phillipa
Posted by linkadge on July 31, 2010, at 23:25:46
In reply to Re: Stereochemistry question (re: citalopram) » linkadge, posted by Deneb on July 28, 2010, at 23:02:54
Thanks Deneb, just one more question (if you don't mind).
So, in citalopram, are the two enatomers in identical ratios.
Linkadge
Posted by ed_uk2010 on July 31, 2010, at 23:25:47
In reply to Re: Stereochemistry question (re: citalopram) » Deneb, posted by linkadge on July 29, 2010, at 8:23:02
> Thanks Deneb, just one more question (if you don't mind).
>
> So, in citalopram, are the two enatomers in identical ratios.
>
> LinkadgeDeneb is correct. Citalopram consists of two different molecules/enantiomers.
For example, a tablet of citalopram 20mg contains 10mg of S-citalopram (now known as escitalopram) and 10mg of R-citalopram.
Posted by linkadge on July 31, 2010, at 23:25:47
In reply to Re: Stereochemistry question (re: citalopram), posted by ed_uk2010 on July 29, 2010, at 17:54:13
Ok, thanks for clarifying that.
Posted by Deneb on July 31, 2010, at 23:25:47
In reply to Re: Stereochemistry question (re: citalopram), posted by ed_uk2010 on July 29, 2010, at 17:54:13
I think it is a 50:50 mixture, but I can't be 100% sure because I don't know the synthesis of citalopram.
There are ways to favor one entantiomer over another but as is the case in nature, sometimes things aren't as clean as they ought to be. I did learn about a technique to make 98% of one enantiomer of one particular molecule, but it also made 2% of the other enantiomer, so it is possible to get a non 50:50 ratio.
Posted by ed_uk2010 on July 31, 2010, at 23:25:47
In reply to Re: Stereochemistry question (re: citalopram), posted by Deneb on July 29, 2010, at 20:07:49
>I think it is a 50:50 mixture, but I can't be 100% sure because I don't know the synthesis of citalopram.
It is, yeah - citalopram (Celexa) is a racemate.
Posted by Deneb on July 31, 2010, at 23:26:06
In reply to , posted by on December 31, 1969, at 18:00:00
Thanks for letting me know! :-)
This is the end of the thread.
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