Page 85 - Practical DF2 Corrected (2)

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

2) Humectants:
o Loss of water from gels may lead to rapid formation of a film on the skin
surface.
o The addition of humectants, such as glycerol, propylene glycol or
sorbitol, enhances the water-holding properties of the gel.

3) Antimicrobial preservatives:
o Water-based gels require a preservative to prevent microbial
contamination.
o The antimicrobial agents most commonly used in gels include methyl
and propyl hydroxybenzoate, chlorocresol, benzoic acid, benzalkonium
chloride, phenylmercuric nitrate and chlorhexidine acetate.
o The selected preservative must be compatible with the gelling agent and
other components of the formulation.

4) Thickening agents:
o Poloxamers are copolymers of ethylene oxide and propylene oxide and
are used as dispersing and suspending agents in a number of licensed gel
formulations.

5) Antioxidants and chelating agents:
o Where the active ingredient is sensitive to oxygen or to heavy metals, a
suitable antioxidant and/or chelating agent (such as EDTA) may need to
be included in the gel.

6) pH Adjusters:
o To adjust the pH of gels, sodium hydroxide or citric acid may be used as
well as other acids or alkalis.

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