Current status of contraceptive vaginal rings.

Contraceptive vaginal rings (CVR) offer a new, effective contraceptive option, expanding the available choices of hormonal contraception. Various ring prototypes have been evaluated: progestin-only rings and combined progestin-estrogen rings, as well as different combination of progestins and estrogens. The progestin-only ring is intended for continuous use, whereas the combined ring has been designed for cyclic 3-week in/1-week out use, although several studies have explored alternative schemes of extended use. However, only two ring designs have reached the market: NuvaRing, a 1-month combined ring that releases etonogestrel and ethinylestradiol, and Progering, a 3-month progesterone-releasing ring for use in lactating women. A one year Nestorone/ethinyl estradiol CVR is approaching the final stages of development, as the Population Council is preparing to submit a new drug application to the Food and Drug Administration. The main advantages of CVRs are their effectiveness (similar or slightly better than the pill), ease of use without the need of remembering a daily routine, user ability to control initiation and discontinuation, nearly constant release rate allowing for lower doses, greater bioavailability and good cycle control with the combined ring, in comparison with oral contraceptives. Current prototypes in development include rings releasing progesterone receptor modulators, which would provide estrogen-free contraception, as well as combined rings releasing estradiol, instead of ethinyl-estradiol, providing a safer profile. Furthermore, intensive efforts towards developing dual protection rings, providing both contraception and protection against reproductive tract infections, offer hope that this greatly needed technology will soon undergo clinical testing and will be in the hands of women worldwide in the near future.