Optimization of eugenol microemulsion for transdermal delivery of indomethacin

The aim was to optimize eugenol microemulsion for transdermal delivery of indomethacin (model drug). Pseudo-ternary phase diagrams were constructed using Tween 40 (surfactant) in presence and absence of ethanol or propylene glycol (PG) as co-surfactants. Microemulsion formulations containing eugenol at 10, 20 and 30% w/w with 60% w/w of surfactant or surfactant/co-surfactant were evaluated for indomethacin loading, release and transdermal delivery. Transdermal delivery was assessed using rabbit ear model. The phase diagrams reflected the ability of Tween 40 to form eugenol microemulsion with addition of ethanol or PG increasing the microemulsion zone. Indomethacin loading in microemulsion was increased by increasing eugenol concentration and in presence of co-surfactants. The release rate increased in presence of PG or ethanol. Indomethacin transdermal flux was greater from microemulsions containing high eugenol concentration with PG containing systems being superior. The study introduced eugenol microemulsion formulations for transdermal delivery and highlighted possible synergism with PG.