[Dexamethasone acetate microemulsions: formulation and effect on skin permeability]

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery Systems
• Dermatology

Background:

• Dexamethasone acetate (DA) topical delivery is often limited by poor skin penetration.
• Microemulsions (ME) offer potential for enhancing the percutaneous absorption of poorly soluble drugs.

Purpose of the Study:

• To optimize an oil-in-water (O/W) microemulsion formulation for dexamethasone acetate (DA).
• To evaluate the impact of the optimized microemulsion on DA percutaneous permeation and skin retention.

Main Methods:

• Screening of oils, surfactants, and co-surfactants for DA solubility.
• Construction of pseudo-ternary phase diagrams to identify the microemulsion region.
• In vitro permeation studies comparing microemulsion and suspension formulations.
• Analysis of skin interaction using Differential Scanning Calorimetry (DSC) and Attenuated Total Reflection Fourier Transformed Infrared Spectroscopy (ATR-FTIR).

Main Results:

• An optimized ME formulation (oleic acid/Labrasol/propylene glycol/water, 8/45/15/32 w/w) was developed with 0.75% (w/w) DA loading.
• The microemulsion exhibited a 6.00-fold increase in DA permeation compared to suspension.
• Skin retention of DA was 4.79-fold higher with the microemulsion formulation.

Conclusions:

• The optimized microemulsion significantly enhances dexamethasone acetate percutaneous permeation and skin retention.
• Microemulsion interaction with stratum corneum lipids and keratin disrupts skin barrier function, facilitating enhanced dermal delivery.
• Microemulsions represent a promising strategy for improving topical drug delivery of dexamethasone acetate.