Regarding enantiomers, which statement is true?

Regarding enantiomers, which statement is true?

• A. They always differ in PK and PD
• B. They never differ in PK and PD
• C. They usually differ in PK and PD
• D. They differ only in color

Answer: (C)

Chirality in drugs means the two mirror-image forms can interact differently with the body's chiral components—enzymes, transporters, and receptors. Because these proteins are stereospecific, each enantiomer can have a distinct fate (PK) and distinct effect at its target (PD). This stereoselective interaction often leads to meaningful differences in how much of the drug is absorbed, distributed, metabolized, and eliminated, as well as how strongly or in what way the drug acts on its target. So, enantiomers usually differ in PK and PD, reflecting common but not universal variation in metabolism and receptor binding between the two forms. An example is that one enantiomer may be cleared more slowly and be more potent at the target, while the other may be less active or cleared differently. The notion that they differ only in color isn’t correct, since chirality substantially influences biological interactions, not just appearance.

Chirality in drugs means the two mirror-image forms can interact differently with the body's chiral components—enzymes, transporters, and receptors. Because these proteins are stereospecific, each enantiomer can have a distinct fate (PK) and distinct effect at its target (PD). This stereoselective interaction often leads to meaningful differences in how much of the drug is absorbed, distributed, metabolized, and eliminated, as well as how strongly or in what way the drug acts on its target. So, enantiomers usually differ in PK and PD, reflecting common but not universal variation in metabolism and receptor binding between the two forms. An example is that one enantiomer may be cleared more slowly and be more potent at the target, while the other may be less active or cleared differently. The notion that they differ only in color isn’t correct, since chirality substantially influences biological interactions, not just appearance.