Posted by Larry Hoover on June 13, 2003, at 22:20:42
In reply to St.JAMES: HELP! Need some DEFINITION assistance!, posted by Janelle on June 13, 2003, at 20:23:12
> Okay, I did a Google search like you mentioned on that r-enantiomer word and yep, it brought up tons of hits. However, as I began clicking on them they also mentioned an "s-enantiomer"!!
>
> Now I am thoroughly confused about these two things and if you could explain them in PLAIN ENGLISH (the hits do not; they're very technical), I sure would appreciate it!
>
> I'm determined to be able to understand the difference between Lexapro and Celexa, the latter of which I'm on, and I just know it boils down in large part to the "enantiomer" differences between the two meds, but I can't get a grip on what the r and s enantiomers are! Thanks.Other posters have mentioned the right and left hand gloves that make up a pair. They're identical to each other if you hold one up to a mirror, and compare it to one not viewed through the mirror.
What may help make good sense of that difference is an application you're familiar with.
When you shake hands with someone, you both hold out your right hands. In that example, one right hand is a properly shaped receptor for another right hand. A left hand doesn't fit a right hand during a hand-shake, even though it has all the parts arranged in a similar way, just arranged with the opposite orientation.
The receptors in our brains which receive neurotransmitters have handedness, which is called chirality. The drugs that best fit a chiral receptor have to have the proper handedness. Chemists call the left and right handed versions of molecules s- (for sinestra) and r- (for recta) enantiomers. If we've figured out that the s-enantiomer is the one doing the major work in blocking e.g. serotonin-reuptake, providing the purified drug (s-enantiomer) at lower concentrations is as effective as providing mixtures of r- and s-enantiomers at higher total concentration. Theoretically, less chance of side effects, at the same potency of treatment.
Lar
poster:Larry Hoover
thread:233801
URL: http://www.dr-bob.org/babble/20030609/msgs/233844.html