Crystallization Behavior of Estradiol in an Acrylic-based Pressure Sensitive Adhesive Matrix

فاقد چكيده

The mechanism of drug release from transdermal drug delivery systems change with the physical state of the active ingredient e.g. to be amorphous or crystalline also dissolved or dispersed. Transdermal patches in different thicknesses and estradiol loadings were prepared using an acrylic adhesive by a knife-coating process, drying and lamination. It was concluded that inclusions observed using optical microscopy through the thickness of adhesive layer contained estradiol crystals. Large surface area of crystalline regions observed for thicker samples was attributed to strong crosslinking capability of estradiol hemihydrate. The crystalline regions were significantly more discontinuous in samples with adhesive layer thickness of 45 μm. This was confirmed by pores observed in the SEM micrographs after drug release. No significant increase was observed in the burst release with increasing of thickness from 45 to 60 μm. Formation of a crystalline layer near the releasing surface was confirmed with a sharp decrease in amount of estradiol released at early times. Late time release rate and its amount were increased with increasing in adhesive layer thickness.