Enhanced Bioavailability of Exemestane Via Proliposomes based Transdermal Delivery

Exemestane, a novel steroidal aromatase inactivator used in the treatment of advanced breast cancer has limited bioavailability (42%) due to poor solubility, extensive first‐pass metabolism, and also the absorption is dependent on formulation type and food. The present study is aimed to evaluate the feasibility of proliposomes for transdermal delivery of exemestane. The prepared proliposomes were characterized for size, zeta potential, and entrapment efficiency. The size of the vesicles was found to be between 440 and 700nm with high entrapment efficiency for the formulation containing greater amounts of phosphatidylcholine. Differential scanning calorimetry and Fourier transform infrared studies were performed to understand the phase transition behavior and mechanism for skin permeation, respectively. The drug release across cellophane membrane follows zero‐order kinetics by diffusion. Ex vivo permeation enhancement assessed from flux, permeability coefficient, and enhancement ratio were significantly higher for proliposome gels compared with control. A significant improvement in the bioavailability (2.4‐fold) was observed from optimized proliposome gel compared with control (oral suspension). The stability data reveal that the formulations are more stable when stored at 4°C. In conclusion, proliposomal gels offer potential and prove to be efficient carriers for improved and sustained transdermal delivery of exemestane. © 2011 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:3208–3222, 2011