Dosage forms are classified into four types on the basis of the following aspects:

1. Physical state
   • Solid
   • Liquid
   • Semisolid
   • Gas
2. Route of administration
   • Oral
   • Parenteral
   • Rectal
   • Nasal
3. Site of application
   • Skin
   • Eye
   • Tooth
   • Hand
   • Foot
   • Hair
   • Nose
   • Buccal
4. Use
   • Internal
   • External

Figure 4.1 shows the classification of dosage forms.