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pubmed:otherAbstract |
PIP: The advances in contraceptive and sterilization methods likely to be available within the next few years will probably consist of improvements of existing methods rather than revolutionary new techniques. Among female vaginal methods, vaginal sponges incorporating spermicides have been constructed of collagen or polyurethane mixed with nonoxynol 9, and an intravaginal contraceptive device consisting of a biodegradable membrane impregnated with spermicide is under development. The spermicidal capacity of propranolol and the capacity of electrolytes such as bisodium phosphate to render the cervical mucus impenetrable to sperm are under study. A cervical cap with a valve to allow cervical secretions to pass has been tested in 140 volunteers over 26 months without problems. New progestin-releasing IUDs which control infection, menstrual blood loss, and dysmenorrhea, quinacrine-releasing IUDs which induce tubal obstruction, IUDs which release antifibrinolytic substances to control menstrual bleeding, postpartum IUDs designed to resist expulsion, and intracervical devices which release spermicides or produce changes in the cervical mucus are in various stages of development. Tubal occlusion through use of chemical agents such as quinacrine and phenolmucilage has not been totally effective in all cases. Achievement of temporary sterility through insertion of small plugs in the tubal ostium has not yet been perfected enough for clinical trials. A removable device which would surround and obstruct the fimbria but which could be removed whenever desired has given promising preliminary results in animal tests. The only new hormonal agent introduced in recent years that has come into wide use is desogestrel, which has twice the progestational activity of levonorgestrel, less androgenic effect, and a better effect on high density lipoprotein cholesterol when combined with ethinyl estradiol than any other currently used hormonal combination. Promising new delivery systems for hormonal contraceptives include subdermal implants, especially the Norplant system which can be left in place for up to 6 years and has a very low failure rate and good tolerance and continuation rates. Vaginal rings containing levonorgestrel and estradiol have given low pregnancy rates in trials but are not expected to be ready for widespread use in the near future. Several different types of biodegradable delivery systems are under development but it is still too early for an evaluation of their advantages. Analogs of luteinizing hormone releasing hormone including buserelin offer promise for future development of contraceptive methods. Other substances that may potentially be used in contraception include inhibitors of the luteal phase or of steroid synthesis, immunologic agents such as placental and trophoblastic antigens, and newly discovered follicular peptides such as ovulation maturation inhibitor. Male contraceptive agents under development include testosterone, gossypol, LHRH analogs, sperm antigens, and sperm inhibitors of vegetal origin.
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