Divisions > Pharmaceutical > Formulation Guides > Topical Emulsions
Emulsions for topical drug delivery
An emulsion is a dispersion of droplets of a liquid in another immiscible liquid (e.g. oil and water) Stability against droplet coalescence is provided by the presence of a surfactant, or so-called Emulsifier.
The benefits of emulsions for topical drug delivery include:
- Solubilisation of water-insoluble drugs into a lipidic vehicle within the formulation
- Increase in the surface area of the interface leading to an improvement in the absorption of the drug
Selecting the right emulsifier
The selection of an appropriate emulsifying base is based on the desired appearance and consistency of the final product, the type of emulsion (O/W or W/O) needed, and the specific characteristics of the active (solubility, physicochemical properties, chemical stability).
The initial approach for selecting the right emulsifier for the drug is by drug solubility screening. You then need to determine:
- How much solubilizer (either hydrophilic or lipophilic) is required to solubilise the drug?
- Which emulsifier can emulsify that amount of solubilizer?
For information on the emulsifying bases we can offer see Emulsifying bases
Gattefossé has determined the maximum amount of lipophilic or hydrophilic phases that each emulsifier is able to disperse. To request this information please contact us.
Once the base has been selected formulation is a very simple process.
- Heat the oily phase (emulsifying base + oils) to 75 - 80°C
- Heat the aqueous phase to 75 - 80°C
- Add the aqueous phase into the oily phase while stirring at 75°C with simple, slow planetary or axial stirring.
Improving the formulation
The pharmaceutical performance and cosmetic appeal of the formulation can be improved by adding
- Permeation enhancers
- Thickening agents
- Emollients to improve the touch
- Preservatives: antioxidant, antimicrobial
For information on additives that can be used to improve the formulation see Thickening agents and emollients
Please contact us or complete an enquiry form to request:
- Product samples
- Gattefossé’s topical excipients brochure
- Further product handling, regulatory and toxicology information
- Details of the technical services offered by Gattefossé’s Application Laboratory