Stereochemistry refers to a branch of chemistry that studies the relative spatial arrangement of atoms within molecules. Some drugs are mixtures of different stereoisomers of a molecule in which only one has the ability to perform the desired function, though both forms contain the exact same chemical composition. Celexa, an antidepressant drug, can exist in two different stereoisomeric forms, in which one is 170 times more effective than the other! Some stereoisomers may even perform different activities. Darvon is used as a pain reliever whereas its stereoisomer, Novrad (Davron spelled backward!), is an anti-cough agent.
