Posted by dennison on September 29, 2002, at 22:09:20
In reply to Lexapro Dosage (vs. Celexa) « yeltom, posted by Dr. Bob on September 29, 2002, at 2:27:57
Hi --Easy answer because isomers have different stereochemistry, and in the world of drug effects stereochemistry is everything. One isomer might be preforming the total effect of the racemic ((r+s)) mixture. Sometimes each isomer has a positive effect, sometimes just one, and of course side-effects as well vary between the 2 isomers or of course could be essentially the same. In the case of celexa the ""s"" isomer was found to be the isomer which actually inhibits the serotonin reuptake while the r isomer was found to contribute more to the side-effects. .............................Now the issue of potency, Isomers can negate the effect of one another also-- so by removing one the attenuating effect of it on the other isomer is removed. Consider the more familiar ex. of dextro and levo amphetamine --dextro isomer is well known to have approx. a 4x CNS potency over the levo form. If the CNS effect was the sought after effect, the dextro isomer would be more potent and thus require a lower dose--Also by removing the l-isomer from and racemic mixture you have twice as much of the ""R"" form................. Whether Lexapro will pan out ""IN THE REAL WORLD"" remains to be seen. Since hype and gimmicks are so common in the pharmaceutical market. Ex.ssri and pre-clinical studies and the side-effect profiles,---- especially the sexual aspects -which were listed as being negliable---yet as we all know rates in 50%>>>70% range are more realistic. :):)
poster:dennison
thread:121478
URL: http://www.dr-bob.org/babble/20020922/msgs/121594.html