Table 1.

Drugs with different properties requiring different delivery systems.

	Drugs
	Small Molecules				Large Molecules
	BCS Class I	BCS Class II	BCS Class III	BCS Class IV	Peptides	Proteins	Nucleic Acids
Molecular weight	↓	↓	↓	↓	↑	↑	↑
Water solubility	↑	↓	↑	↓	↔	↔	↔
Cell permeability	↑	↑	↓	↓	↓	↓	↓
Half life	↕	↕	↕	↕	↓	↓	↓
Main delivery route	Oral	Oral	Oral	Oral	Parenteral	Parenteral	Parenteral

BCS: Biopharmaceutics Classification System

↓: Low

↑: high

↔: Acceptable

↕: Individual variation from low to high