Microemulsion is a promising transdermal drug delivery
vehicle. Incorporation of cosurfactant in the microemulsion formulations
will not only affect the physical characteristics of
the microemulsion but will also influence the transdermal drug
delivery efficacy. The physical effects range from reduced viscosity,
reduced droplet size to increased drug loading capacity.
The presence of cosurfactants enhanced the transdermal drug
delivery from microemulsion. The overall effects depended on
the type of cosurfactant with ethanol being the most efficient
among the tested cosurfactants.
oil, 20% water and 60% of either Tween 80 or 1:1 surfactant/cosurfactant mixture were compared. Incorporation of cosurfactants expanded the
microemulsion zone. 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.