Core50: Classification of drugs according to chemical structure and complexity

⚗️ High-yield / 要点：Drugs can be classified by physical form, stereochemistry, and molecular size/complexity. Structure matters because different stereoisomers can have different potency and safety.

Physical nature / 物理的性質

Form	Examples
Solid	Most tablets: aspirin, statins, antidepressants
Fluid/liquid	IV anesthetics such as propofol; IV antibiotics
Gas	N₂O / nitrous oxide

Chemical structure: stereoisomerism / 化学構造：立体異性

• Shape/spatial arrangement can change pharmacologic activity.
• One enantiomer may be more active or safer than the other.

Drug	Stereochemistry point
Carvedilol	(S)(+) is a potent β-receptor blocker; (R)(−) is much less inhibitory
Ketamine	(S)-ketamine is more potent; has acute antidepressant effect
Citalopram	(S)-form is escitalopram; more effective with fewer side effects
Cetirizine	Levocetirizine is the active eutomer of racemic cetirizine

Molecular size / 分子量による分類

Class	Approximate molecular weight	Examples
Small molecules	<1000 Da / <1 kDa	Aspirin ~151 Da; many current medicines
Large molecules	>1 kDa	Hormones, proteins, monoclonal antibodies

Large molecule examples / 高分子薬の例

• Insulin：~5.8 kDa.
• Adalimumab：~144 kDa.
• Large molecules often include proteins and monoclonal antibodies.

Remember / 覚え方

• Form matters: solid/liquid/gas
• Stereochemistry matters: one isomer may be better
• Small molecule <1 kDa; biologic/large molecule >1 kDa