Apart from being mirror images, do enantiomers have different properties?

Enantiomers can have different properties. Even though their physicochemical properties are the same, enantiomers may have different effects on biological systems. The reason for this is that biological structures normally only fit with one of the possible stereoisomers of a molecule. Drugs work by interacting with these chiral biological structures (receptors, transporters, ion channels, etc.). Therefore, different enantiomers of a drug often have different activities at their molecular target. To continue the right and left hand analogy, right-handed scissors cannot be used correctly with the left hand and vice versa.

These different properties can result in the following:

• one enantiomer may be active, the other inactive
• one enantiomer may act as an antagonist to the action of the other
• both may be active but exhibit different properties
• one enantiomer may be pharmacologically active and the other toxic.
• In practice: enantiomers can, and should, be evaluated on individual merit, on a drug-by-drug basis.