Leigha, if you just type isomers into a search engine, you may have to wade through a lot of stuff, but you should eventually come to a better understanding of the concept than I could possibly write here.
Basically it is that the body compensates for changes in the brain and other organs whose purpose is to alert the body to dangerous stiumli by causing a more intense response the next time the organ encounters that stimuli. Pharmaceuticals that do not change the stimulus, but change only the body's response to it produce mirror images of the response that they are designed to alter.
I know that is as clear as mud, but it is scientific fact. Read any package insert with a pharmaceutical and you will almost always find the condition that is being treated listed as a possible side effect. That is the result of isomers.
Long boring story.
smile

[ May 02, 2005, 03:41 PM: Message edited by: smilinize ]