[Intravaginal pharmaceutical dosage forms: present and future choice. II. Barrier methods and vaginal rings]

The female barrier methods--vaginal diaphragms cervical caps vaginal sponges and the female condom--are gaining more interest due to their ability to protect against sexually transmitted diseases (STDs) especially AIDS. They prevent sperm from entering the cervix and the uterine cavity. A relatively few types of drugs can be administered through the vagina. These include antifungal drugs antibiotics antiseptics and contraceptives. Even though oral contraceptives (OCs) will continue to be used for a long time in their present form the need for new contraceptive methods seems to grow stronger in family planning programs in developing countries or in women wanting methods other than the existing methods. For the most part vaginal rings are still in the research stage and have certain advantages in terms of insertion and removal by the patient. They continually release an effective dose of a hormone while assuring better user compliance. Systematic administration of drugs by the intravaginal route is well accepted. Since these systems avoid the hepatic system and the fluctuations in concentrated plasma observed with OC use they require a lower dose of hormones leading to a reduction in undesirable effects. Vaginal rings can contain different progestins (levonorgestrel 3 keto-desogestrel) which may or may not have an estrogen (estradiol ethinyl estradiol). Vaginal rings are made up of one or two layers of silicone polymer which contain the active hormone(s). Some rings have separators to prevent contact between the different hormones. Perhaps in the near future the new contraceptive systems (e.g. vaginal rings) will take a substantial place among the contraceptive methods based on their efficacy their cost and the improvement in acceptability by the patient. Contraception research is still necessary because despite the effectiveness of a method it is unlikely that it is able to become universal.