Posted by Larry Hoover on April 6, 2003, at 13:56:27
In reply to Re: HELP! Difference between Lexapro and Celexa!, posted by mopey on April 6, 2003, at 13:23:46
> Hi. I tried Celexa and was fine for four weeks or so, then got VERY sleepy midday and couldn't function.
>
> I've heard the Lexapro is a modified version of Celexa and it supposedly has less side effects.
>
> I've been thinking about trying that next -- am currently "on hiatus" from meds.
>
> OK, I know other people will post more scientific explanations, but thought I'd throw in my two cents.
>
> Good luck!You'll need Adobe Acrobat to view them, but there are images of the two forms of citalopram (and more than you probably wanted to know about the chemistry), here:
http://www.cipralex.ch/pdf/poster/sanch_401.pdf
http://www.psychiatrist.com/pcc/pccpdf/v04n01/v04n0107.pdf
Lexapro is just one of the two forms, the S-enantiomer, dubbed Escitalopram. Rather than re-invent the wheel, here's a good explanation, from:
http://www.leeheymd.com/medmemo/currentmm.html
"Many, but not all, molecules or chemicals whether developed in a chemistry lab or occurring naturally exist in or can be produced in 2 or more forms (isomers) whose structure differs only in how they look in three dimensional space. The key is whether one or more carbon atoms in the chemical's structure is bonded to other elements in a way that they can be rotated in space or that they rotate polarized light shown through the chemical. Such carbon (and occasionally nitrogen) atoms are referred to as a chiral center. If there is one chiral center there will be two isomers. If there are two chiral centers there will be four isomers - and so on. Although enantiomer is the proper term for these slightly variant forms, the term stereo isomers is almost as accurate - but for simplicity I'll use the term isomer in this article. These subtle spatial arrangement differences can make important differences in the chemical's function and its effects.
This is easier to understand than it may sound at first. Let's use your hands as an example. Although your right and left hands are both hands and appear essentially identical they are actually mirror images of each other. Your right hand does not exactly match your left (and vice versa) unless you look at it in a mirror. Thus, you have two forms, two structures, or isomers, of one object - the human hand. The human hand exists in 2 forms. This is also true of your ears, gloves, feet, shoes, and sides of your face, etc. What's really important though for our topic here is that the 2 forms (isomers) of this one object, your hand, function differently solely because of that seemingly minor mirror image difference. If you shake hands with someone you both use your right hands and they fit very nicely together. If you try to "shake" or join your left hand with your or someone else's right hand (or vice versa) it doesn't work. The same can be true of medicines. Very small differences in the three dimensional structure of the same medicine, neurotransmitter, receptor, etc., can greatly effect whether and how they work. It's similar to a very small change in a key causing that key to not fit into the lock. This is how neuro-transmitters carrying a message from one nerve cell to the next cell's receptor works - or doesn't work (fit). The name of these new isomer forms of the generic medicine is changed by adding a prefix showing whether the isomer is the left or right handed mirror image version or in which way polarized light shown thru the chemical is bent or turned (rotated).
Now, let's take the example of Lexapro and Celexa. Celexa is the brand name of the medicine citalopram which is used to treat depression and anxiety. Celexa is a racemic mix of the two isomer forms of citalopram. When all isomers are present it is called a racemic mix or racemate. It turns out that the left handed version of citalopram, named escitalopram, is more effective, potent, has even less negative interaction effects, may be faster to work, and has less side effects than either the right handed isomer version or the original citalopram (Celexa) parent mixture. Thus, the company which made Celexa has used advanced techniques to produce pure escitalopram, which they brand named Lexapro. Lexapro has been approved by the FDA based on effectiveness and safety studies, the company gets an extended patent, and we get an improved refined form of an already good medicine. Of course, time and clinical experience will reveal just how good it is. Lexapro is expected to be available in, or soon after, September 2002. "
poster:Larry Hoover
thread:216551
URL: http://www.dr-bob.org/babble/20030402/msgs/216700.html