Page 84 - Practical DF2 Corrected (2)

Pharm D Clinical Pharmacy program 2024-2025 Level 2, Semester 2 Pharmaceutical Dosage Forms II (PT 405)

Gel

• The most common types of pharmaceutical gels are single phase systems
where macromolecules (gelling agents) at low concentration are uniformly
distributed throughout a liquid. The macromolecules form an interconnected
network to give a rigid structure into which drug can be incorporated.
o The gelling agent used will depend on the physicochemical properties of
the drug and compatibility with other excipients, including the solvent.

• Single-phase gels may be made from naturally occurring substances or from
synthetic macromolecules.

• Although gels are commonly aqueous (hydrogels) or contain water and
alcohols (hydroalcoholic gels), a number of alcohol-based gels are also
commercially available.

• The viscosity of the gel may be varied depending on the amount and/or
properties of the gelling agent.

• Gels ingredients:

1) Gelling agent:
o The gelling agent used will depend on the physicochemical properties of
the drug and compatibility with other excipients, including the solvent.

A) Gelling agents derived B) Synthetic gelling agents
from animals and plants
• Gelatin. • Carbomers.
• Pectin. • Polyvinyl alcohols.
• Sodium alginate. • Cellulose derivatives such as:
• Starch.
• Tragacanth. methylcellulose, sodium
carboxymethylcellulose (Na CMC)
and hydroxypropyl methylcellulose
(HPMC).

o Gels produced with cellulose derivatives are more resistant to microbial
attack compared with gels prepared using the naturally occurring gelling
agents; they also show high clarity and good residence time on the skin.

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