The cosurfactant free microemulsion was viscous showing pseudo-plastic flow. The cosurfactant containing preparations were
less viscous with Newtonian flow. The drug loading and release rate were increased in the presence of cosurfactants with the release depending
on the viscosity. Incorporation of hydrocortisone in microemulsion increased the transdermal flux compared to saturated aqueous solution. The
presence of cosurfactants increased the transdermal drug flux compared to the cosurfactant free formulation. Ethanol produced the greatest effect
followed by propylene glycol and isopropanol. The presence of cosurfactant and its type can thus affect both the phase behavior and the transdermal
delivery potential of microemulsion.