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Abstract
This study investigated the transdermal delivery of indomethacin (model drug) from
self-microemulsifying system, microemulsions and their phase transition systems. The
study selected five formulations with fixed surfactant-oil ratio and increasing water
content. These included a water free self-microemulsifying drug delivery system (SMEDDS),
microemulsions containing water at 5% (w/w) (ME 5%) or at 10% (w/w) (ME 10%), a liquid
crystalline formulation containing water at 30% (w/w) (LC) and coarse emulsion containing
water at 80% (w/w) (EM). To clarify the results the study evaluated a microemulsion
containing 10% (w/w) of receptor fluid (30%, v/v ethanol in phosphate buffered saline,
PBS) (MEEB 10%) and a supersaturated system of ME 10% (MESS 10%). The viscosity increased
with increasing water content up to certain limit above which the viscosity started
to reduce. These formulations increased the transdermal drug flux compared to saturated
drug solution in PBS (control) with formulation being ranked as SMEDDS > MEEB 10%
approximately ME 10% approximately ME 5% > LC > EM > control. SMEDDS produced the
longest lag time. The MESS 10% produced a flux value similar to that of SMEDDS but
with shorter lag time suggesting transformation of SMEDDS into microemulsion after
topical application with possible supersaturation. These systems can provide the formula
with high flexibility in selecting the optimum viscosity as the tested preparations
were able to enhance transdermal delivery in the range between SMEDDS, ME and the
LC preparations with some enhancing ability for the EM.