RESEARCH | Article Examines Latest Developments in Contraceptive Technology
[Jan. 29, 2009]
Summary of "New Technologies in Contraception
," S. Rowlands, International Journal of Obstetrics and Gynecology
, January 2009.
More than 200 million women in developing countries do not use any form of contraception, or use only traditional methods. Technological advances in contraception are of limited value to these women unless their governments can supply their populations with contraceptive services. Governments and individuals should work toward the Millennium Development Goal target of universal access to reproductive health services by 2015 through the primary health care system, Rowlands writes.
Contraceptive use varies considerably among women around the world, ranging from 3% in Chad to 90% in China among women ages 15 to 49 who are married or in a union. Effectiveness of contraceptive methods also varies widely, and simultaneous use of a barrier method combined with a second method -- known as dual protection -- dramatically reduces the risk of pregnancy and of contracting a sexually transmitted infection. The author writes that many women and men see choosing a contraception as "a matter of finding the 'least worst' option, balancing effectiveness, and ease of use against perceptions and expectations of adverse effects and health risks." Assessment of Methods
Rowlands reviews recent developments in several methods of contraception. Oral and Emergency Contraception
Advancements in oral contraception have come in the form of newer progestogens, which aim to enhance or develop positive attributes of existing progestogens or reduce or eliminate negative attributes. Meanwhile, dosage levels of both estrogen and progestogen have decreased significantly in recent years. Ethinylestradiol -- or EE -- has been the main estrogen used in combined pills in the past, but further work is being done on the use of estradiol (E2) in the combined pill. Another estrogen -- estetrol (E4) -- could be protective against breast cancer and is 18 times less potent than EE, meaning it would present less potential for adverse effects. Extended use of the combined birth control pill has become widespread.
There also have been trials of mifepristone as a daily oral contraception, which showed no pregnancies in 356 months of use and less spotting than with a progestogen-only pill. Because many women prefer to have predictable or no menstrual bleeding, there are significant advantages to the development of estrogen-free contraception in terms of acceptability, the author writes. Mifepristone combined into one dose also has shown efficacy as emergency contraception; however, no pharmaceutical company has pursued marketing the drug for this purpose because of the political connotations of its abortifacient effect, he writes. Vaginal Rings
Vaginal rings offer several advantages, including that the steroid absorption is rapid, the release rate is constant, the method is under the woman's control and the ring can be removed for sex for up to 2 hours. Comparative trials of the vaginal ring show efficacy at the same level as the pill with high adherence. The Population Council is conducting a preliminary investigation into the use of nestorone in vaginal rings, which is ineffective orally but is sufficient for contraceptive efficacy when given in low, systematic doses.Implants
According to the author, there have been considerable improvements in implant technology. Newer systems consist of either one or two implants that are more robust and will not tear or divide as easily as earlier polymer systems, which consisted of six capsules that could be difficult to insert and remove. A single-rod nestorone implant, which has completed two phases of trials in the U.K., has shown to provide contraception for two years, and a biodegradable implant that would eliminate the need for removal is being studied. Transdermal Administration
The development of matrix technology has made it possible to deliver both EE and progestogens transdermally in the form of a patch. A combined EE/norelgestromin patch is now widely available, and adherence has been better than with the combined pill, especially among teenagers. An experimental patch that combines gestodene and EE has been shown to suppress ovulation over two cycles, and nestorone is under preliminary evaluation for transdermal use in the form of both a gel and a spray. Intrauterine Devices
Extensive trials have shown IUDs and intrauterine systems (IUS) to be highly effective, and their long-term nature makes them particularly cost-effective. Work continues on the development of frameless IUDs, which could decrease blood loss and pain associated with plastic frames. However, frameless systems would require new training and a high level of skill for insertion. Two versions of frameless IUS are in development, but currently there is no published data on the contraceptive efficacy of the devices.Spermicides
Much effort has been devoted to the development of spermicides that have additional microbicidal properties that could protect against sexually transmitted infections. The author calls for the replacement of the current long-used spermicide nonoxinol-9 (N-9), adding that there is no evidence that it improves efficacy with condoms. In addition, in some populations, N-9 can possibly lead to increased risk of acquiring HIV or other infections. Two experimental spermicides with microbicidal properties have reached clinical trials in the U.K. for pregnancy prevention. There also has been research into identifying pure microbicides without spermicidal properties by women wishing to achieve pregnancy to use.
Meanwhile, a pilot study is examining the potential for a vaginally administered gel with microbicidal properties that could be used as emergency contraception. The gel is effective in preventing ovulation and "has the potential for providing dual protection when used before sex, thereby putting women more in control," the author writes. Male and Female Barrier Methods
Non-latex condoms are now available, which have a longer shelf life than latex condoms and can be used in the presence of oil-based lubricants. These products have a high acceptability and are nearly as effective in preventing pregnancy as latex condoms, although they are more likely to split or slip off.
Since the introduction of the polyurethane female condom (FC1) in 1992, additional products have been tested using different materials and designs to reduce costs. The FC2 female condom has a less-expensive manufacturing process than FC1, while the VA feminine condom -- also known as the Reddy condom or V-Amour -- has a higher acceptability than FC1. The Program for Approved Technology in Health also has developed a female condom with a dissolvable capsule that makes insertion less difficult; acceptability studies are "promising," according to the author. However, in general, there is little efficacy data available for newer female barriers, he writes. Male Hormonal Methods; Vaccines
There still is no hormonal method for men after two decades of research. The author writes that it is "disappointing" that both pharmaceutical companies that had been funding research and trials of male hormonal methods have withdrawn their funding, most likely because of poor profitability potential and the possibility of legal action from men for whom the method fails. Similarly, "[d]espite extensive efforts, the quest for a contraceptive vaccine has been largely unsuccessful so far," the author writes. One vaccine completed Phase-II trials in the U.K. but was not efficacious. Female and Male Sterilization
Mechanical female sterilization devices, such as plugs and thermal occlusion, have shown limited success and some adverse effects in studies. However, two "hybrid" sterilization methods -- the Essure microcoil device and the Adiana procedure -- have shown much more success. Essure involves inserting coils into the fallopian tubes; fibrosis develops around the coil, leading to tubal occlusion. Adiana, which is still in development, is a two-step procedure that involves thermal damage of the endosalpinx, followed by insertion of a plug.
For men, reversible inhibition of sperm under guidance (RISUG) -- a gel injected into the vas -- is being developed in India. An intra vas device also has been developed, which consists of silicone plugs that are implanted into the vas. Discussion
All but two contraceptive methods are designed for women, Rowlands writes, adding that the development of male hormonal methods has been delayed because of withdrawal of pharmaceutical support. "One has to question the philosophy of the pharmaceutical industry in not comprehensively supporting research into contraception, which can do so much to promote reproductive rights and to relieve suffering of millions of women and their families worldwide," he writes.
Greater progress has been made in the development of new delivery systems than in the synthesis of new hormones. There are now six different delivery routes for hormones, including oral, injection, implantation, vaginal, transdermal and intrauterine. The author also notes that mifepristone has the potential to be oral contraception and emergency contraception, but opposition from the public and political groups has undermined development, making it unlikely that the industry will invest in research. The author suggests that a possible solution to this is the development of a progesterone receptor modulator without abortifacient properties.
The information contained in this publication reflects media coverage of women’s health issues and does not necessarily reflect the views of the National Partnership for Women & Families.