Gels are homogeneous, semisolid preparations used in transdermal drug delivery systems consisting of medicaments dispersed in a suitable hydrophilic or hydrophobic base. Common gel bases include aqueous, non-aqueous, and hydro-alcoholic vehicles. Gelling agents like tragacanth, pectin, starch, and gelatin are added to the base to form a weakly cohesive internal structure and thicken the solution without making it stiff. These gels can include additional components like antioxidants, preservatives, and stabilizers.

1. TRANSDERMAL DRUG
DELIVERY SYSTEM
GELS AND MAGMAS

2. GELS
WHAT ARE GELS?
• Gels In Pharmaceuticals are Homogeneous, Semisolid preparations usually
consisting of solutions or dispersion of one or more medicaments in suitable
hydrophobic and hydrophilic bases.
• Suitable gelling agents are used for the preparation of gels.
• Antioxidants, Preservatives, and Stabilizers may be added to the gels.
VEHICLES USED:
• Aqueous
• Non-aqueous
• Hydro-alcoholic
• Alcohol base

3. GELING AGENTS:
• Gelling agents, also known as solidifiers, gel-forming agents when dissolved in a
liquid phase as a colloidal mixture forms a weakly cohesive internal structure.
• They are organic hydrocolloids or hydrophilic inorganic substances.
• Gelling agents also function as stabilizers and thickeners to provide thickening
without stiffness.
EXAMPLES:
• Tragacanth
• Pectin
• Starch
• Gelatin
• Cellulose derivatives
• Polyvinyl alcohol
• Acacia