Se

basement membrane pillaries

Figure 9.41 (a) Anatomy of the urethra and vagina; drug-delivery systems for both are available. (b) For other than local vaginal treatment, transport through the absorbing membrane structure (squamous epithelium (SE) lamina propria (LP) and muscularis (M) (not shown)) is important in securing systemic levels of drug; inadvertent absorption after local therapy is, of course, possible.

material in the vagina which will inhibit absorption. The uterine and pudendal arteries are the main sources of blood to the vagina; the venous plexus which surrounds the vagina empties into the internal ileac veins. Lymph vessels drain the vagina, and vaginal capillaries are found in close proximity to the basal epithelial layer.

Proteins and peptides, particularly in the presence of absorption enhancers, can be successfully administered by this route, although surfactant-based enhancers are apparently not effective in the vagina. Vaginal enzymes, especially the proteases, are likely to present problems in the vaginal delivery of proteins and peptides.

9.8.1 Delivery systems

Conventional vaginal delivery systems include vaginal tablets, foams, gels, suspensions and pessaries. Vaginal rings (Fig. 9.42) have been developed to deliver contraceptive steroids. These commonly comprise an inert silicone elastomer ring which is covered with an elastomer layer containing the drug. In some systems a refinement has been to add a third, rate-modifying layer to the external surface of the ring as shown. Some systems contain both an oestrogen and progestogen.

Hydrogel-based vaginal pessaries to deliver prostaglandin E2 (to assist in ripening of the cervix prior to labour) progesterone and bleomycin have been developed.

Tablets for vaginal use have included hydroxypropylcellulose or sodium carboxy-methylcellulose and poly(acrylic acid) (such as Carbopol 934) as excipients. Micropatches in the size range 10-100 ^m in diameter prepared from starch, gelatin, albumin, collagen

Compartment with 3-keto-desogestrel + ethinylestradiol

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