Topically applied devices for controlled release

This section considers the design and performance of an intravaginal device for the controlled delivery of an agent that is active at the mucosal surface. The goal is to produce a delivery system that is easily self-administered and provides long-term (i.e., one month) protection against disease or unwanted pregnancy. 

1 Delivery of Agents to the Female Lower Reproductive Tract 

The fluid within the lower reproductive tract originates from variety of sources. The vaginal epithelium produces a small amount of fluid, which is bacteriostatic because of its high acidity (pH 3 ). This acidic fluid mixes with mucus, which is produced at the cervix, to create an overall acidic environment (pH 5-7) within the lumen of the vagina. The cervix produces 20-60 mg of mucus per day, with as much as 1 g/day during mid-cycle. The overall volume of vaginal fluid appears to be 2 to 8 mL/day [40]. 

The simplest mechanism of delivery is insertion of a bolus dose, in which the agent is suspended into a fluid and directly deposited within the vaginal lumen. This method is used currently for spermicide and antifungal drugs. Bolus delivery is a convenient method however, the duration of efficacy is limited. To utilize bolus delivery effectively, the initial dosing requirements (volume and concentration) and the duration of efficacy must be determined. 

This mass was then used to calculate the concentration of agent in the mixture 

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