The model retinoid adapalene was formulated in a novel invasomal dispersion as a topical drug delivery system for
transport of the active pharmaceutical ingredient (API) into hair follicle orifices. In this study, we investigate the preparation of
Adapalene loaded invasomes by mechanical dispersion technique with different ratio of terpenes added as penetration
enhancers. The formulation was characterized for particle size, zeta potential, entrapment efficiency and drug release properties.
This dispersion is then incorporated into HPMC gel to prepare as a invasomal gel formulation properties. The resultant
formulation invasomal gel was evaluated for drug content, pH, spread ability, viscosity in vitro drug release, skin permeation
and rheological behavior. The TEM photograph revealed that the carrier systems are spherical in shape. The particle size
analysis indicated that the size of vesicles increased with increasing the amount of terpenes in the vesicles: the size of
invasomes containing 0.5 % Terpene A formulation was 132.5±0.56 nm, while the size of in vasomes containing 1.5% terpenes
was 159.2±0.32. The entrapment efficiency of Adapalene loaded invasomes ranged from (40-80%). Prepared gel was inspected
under black and white background and was found very clear and without any aggregates. After all evaluation it can be
concluded that Adapalene invasomal gel could increase the drug permeability across the membrane and fast release of the drug
could be achieved successfully