Intravaginal & Intrauterine Drug Delivery Systems
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Controlled-release intravaginal systems are used for delivery of contraceptive steroid hormones.
INTRAVAGINAL & INTRAUTERINE DRUG DELIVERY SYSTEMS
Controlled-release intravaginal systems are used
for delivery of contraceptive steroid hormones. The advantage of this route
includes—no first-pass effect, improved bioavailability and lesser drug dose in
comparison to that required by oral route. Two types of devices have been
developed—a matrix diffusion controlled device e.g. medroxy progesterone
acetate dispersed in viscous silicone elastomer, and the other, dissolution
controlled device e.g. dispersion of a progestin and an estrogen in an
Fig. 14.21 Schematic representation of a
vaginal ring
The device is generally
prepared by extrusion of the resultant composition into a doughnut shaped
vaginal ring (Fig. 14.21). The system releases the medicament for 21 days to
achieve a cyclic intravaginal contraception.
Intrauterine route is also used for fertility
control. Two types of medicated intrauterine devices (IUDs) have been developed
to produce effective contraception for 12 months or more.
1. Copper Medicated IUD
It consists of a polypropylene or polyethylene plastic support of number 7 or letter T with certain amount of copper wire wound around them. T shape IUD is popular since its shape conforms to the uterine cavity and resists displacement and rotation within the cavity as well as expulsion from the cavity (see Fig. 14.22a). The copper wire of surface area 200 mm2 shows maximum contraceptive activity. Oxidation of copper in the body fluids releases its ion slowly and exert its effect locally. The device is effective for more than 3 years.
2. Progesterone Releasing IUD (Progestasert)
It is also a T
shaped polyethylene device with a progesterone reservoir dispersed in a
silicone polymer placed in the vertical arm which is enclosed in a sleeve of
rate-controlling membrane of ethylene-vinyl acetate copolymer (Fig. 14.22b). The device releases progesterone at
a rate of 65 mcg/day for a period of one year.
Fig. 14.22 Contraceptive IUDs—(a) Copper T
located in the uterus, and (b) Progestasert
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