Novel gel-like microemulsion for topical delivery of Amphotericin B

The aim of the present work was to develop a ME for topical delivery of Amphotericin B (AmB). Microemulsions (MEs) are versatile systems to solubilize drugs due to the presence of both a hydrophobic and a hydrophilic region, as well as a distinctive interface composed of surfactant and cosurfactant. MEs have been reported for many advantages for topical application of drugs. Considering that AmB has very low water solubility a screening of surfactants and oils was performed. A gel-like ME system, that can be applied topically without the need for thickeners agents, was selected. AmB was incorporated up to 1 mg/g and remained stable for at least 90 days both at 4 ºC and room temperature, so this formulation would be appropriate as a compounding medication. An in vitro skin penetration test was performed, the applied dose penetrated (10.16 ± 0.01 μg/cm2/h as estimated flux) and remained completely within the skin during the assay; AmB was not detected in the receptor
compartment. In vitro antifungal and antileishmanial activity was tested and drug showed proper activity. AmB is a second line drug for the treatment of cutaneous leishmaniasis, but topical dosage forms are still lacking. This system is potentially useful for the treatment of skin infections avoiding drug toxic systemic effects.