PENETRATION ENHANCEMENT FOR POLYPEPTIDES THROUGH EPITHELIA .D. ROUTES OF DELIVERY - CASE-STUDIES .8. THE VAGINAL ROUTE OF PEPTIDE AND PROTEIN DRUG DELIVERY

Over the last twenty years, more attention has focused on the vagina as a favourable alternative site for the systemic delivery of therapeutic peptides and proteins. The present review aims to discuss the anatomy and physiology of the vagina and the factors which will affect drug transport across the vaginal epithelium. Emphasis is also placed on the characteristics and suitability of various animal models used in the study of vaginal absorption. The literature concerning the vaginal absorption of luteinizing hormone-releasing hormone and its analogues and insulin is reviewed in detail together with work performed using insulin in our laboratories. Due to the physicochemical characteristics of polypeptides and the potential for enzymatic degradation, vaginal absorption of these drugs is normally low. Hence, the need for absorption enhancers in the administration of polypeptides and their histological implications are discussed. Finally, the need for the development of novel delivery systems suitable for peptide administration is also stressed.