Stereochemistry is very important in pharmaceuticals because the 3D arrangement of atoms in a drug molecule can drastically affect its biological activity, safety, and effectiveness. Here’s a explanation:
1. Biological Activity
- Many biological molecules (enzymes, receptors, DNA) are chiral.
- Only one stereoisomer of a drug may fit properly into the biological target.
- Example:
- Thalidomide: One enantiomer had sedative effects; the other caused severe birth defects.
- Cisplatin: Only the cis isomer is effective as an anticancer drug; the trans isomer is inactive.
2. Drug Safety
- Wrong stereoisomers can be toxic or inactive.
- Controlling stereochemistry ensures that only the therapeutically useful isomer is administered.
3. Drug Efficacy
- Stereochemistry can influence absorption, distribution, metabolism, and excretion (ADME) of the drug.
- Example: One enantiomer might be metabolized faster or bind more tightly to the target.
4. Regulatory Requirements
- Regulatory agencies like the FDA require stereochemical purity for many drugs because the wrong isomer can cause adverse effects.
5. Stereochemistry in Drug Design
- Chemists design drugs with specific stereochemistry to maximize efficacy and minimize side effects.
- Chiral catalysts or chiral synthesis methods are often used to produce the desired stereoisomer.
In short:
Stereochemistry ensures that drugs are effective, safe, and selective. One 3D arrangement can be therapeutic, while another can be harmful or useless.