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2. Hydrophobic Gels (Organogels)

▪ Good spreadability, weak occlusion, not widely used

▪ They have a potential use in pharmaceuticals, cosmetics and food industry

▪ Examples of gelling agents:

➢ Sorbitan monostearate (Span 60)
➢ Eudragit
➢ Plastibase (liquid paraffin with polyethylene or fatty oils gelled with colloidal silica or
zinc stearate)
Type II gels
• The vast majority of gels used as dosage forms are type 2
• The commonly used polymers for the formulation of type 2 gels are cellulose derivatives,
alginates and poly(acrylic acid)
• Gels are normally formed by increasing polymer concentration and, if the polymer is ionic,
by altering the pH

Manufacture of pharmaceutical gels
1. Fusion method
2. Cold method
3. Dispersion method

❑ MC and poloxamers have better solubility in cold water
❑ Bentonite, gelatin, and Na CMC are more soluble in hot water
❑ Carbomer and tracaganth are soluble in luke water
❑ Carbomers require a neutralizing agent to create the gel after the gelling agent has been

wetted in the dispersing medium
❑ Most gelling agents require 24-48 hours to completely hydrate and reach maximum viscosity

and clarity
❑ Gelling agents are used in concentrations of 0.5% up to 10% depending on the agent
❑ It is easier to add the active drug before the gel is formed if the drug does not interfere with

the gel formation
❑ Poloxamer (Pluronics®) are copolymers of polyoxyethylene and polyoxypropylene. They

will form thermoreversible gels in concentration ranging from 15% to 50%
❑ In the manufacture of pharmaceutical gels, generally the water soluble

components/excipients are initially dissolved in the vehicle in a mixing vessel with
mechanical stirring
❑ The hydrophilic polymer must be added to the stirred mixture slowly to prevent aggregation
and stirring is continued until dissolution of the polymer has occurred. It should be noted
that excessive stirring of pharmaceutical gels results in entrapment of air
❑ Carbopol, MC and HMC are the only gelling agents used in oral dosage forms

Formulating Poloxamer Gels

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