For years, researchers have worked to develop nonsurgical female and male sterilization methods that would be inexpensive and easy to administer. While some methods currently under study hold promise, none are likely to be widely available in the near future.
For women, possible nonsurgical sterilization methods include adhesives or chemicals that could be inserted via the cervix to block the fallopian tubes. For men, nonsurgical sterilization techniques include the injection of silicone, polyurethane or other substances to block the vas deferens.
Experts say that, particularly in developing countries, a nonsurgical method of male or female sterilization would be beneficial for several reasons. Shortages of facilities, physicians and anesthesia specialists in rural areas create a barrier to surgical sterilization.
In addition, a nonsurgical method might help allay concerns of men and women who fear surgery, cannot afford hospitalization, or who cannot find transportation or child care during surgery and recovery.1 For example, FHI studies in Brazil, Honduras and Guatemala found that surgery costs, travel time and family-related constraints were among the reasons couples did not seek sterilization.2
Quinacrine
One of the most widely studied chemicals for female nonsurgical sterilization is quinacrine hydrochloride, a drug once used to prevent malaria and other parasitic diseases. Quinacrine pellets are inserted through the cervix using a modified IUD inserter or similar device. As the quinacrine dissolves, the fallopian tubes become inflamed, resulting in scarification and closure of the tubes. Up to three insertions may be necessary to achieve complete tubal closure.
Extensive data show quinacrine has promise as a nonsurgical method. However, most international reproductive health organizations have recommended that quinacrine for sterilization not be used in humans until its safety can be established through animal carcinogenicity and toxicology studies, and through epidemiologic studies in women who have been sterilized using quinacrine. FHI fully supports this position.
There are several unresolved safety concerns, including the long-term risks of cancer, potential damage to a fetus if inadvertently administered to a pregnant woman and the possible increased risk of ectopic pregnancy. In addition, participants at a 1994 meeting on female sterilization, organized by the World Health Organization (WHO), recommended that any future studies consider the drug's mechanism of action and standard dosage, as well as the impact of age and parity on efficacy and quinacrine's effects on upper genital tract infections.
During the 1970s and 1980s, FHI researchers helped develop quinacrine pellets and worked with in-country scientists to conduct clinical trials in Chile, India and the United States. In 1990, FHI discontinued prospective quinacrine studies after eight cancer cases were identified during long-term follow-up of 572 Chilean women who had received quinacrine pellets. FHI carried out a retrospective follow-up study of 1,492 women in Chile who received quinacrine from 1977 to 1989 and found no link between quinacrine use and cancer, but additional follow-up studies were recommended.3
In 1994, at the request of the Vietnamese government, FHI began an ongoing retrospective study of a sample of 31,781 women who had been sterilized with quinacrine in Vietnam. FHI also collected data from a randomly selected sample of 1,800 women sterilized with quinacrine to compare their perceptions, experiences and satisfaction levels with women who used IUDs. FHI continues to follow these women.
Other female methods
Other methods of female nonsurgical sterilization under development use different blocking agents -- such as iodine and silicone -- and other delivery systems to reach the fallopian tubes, such as hysteroscopes and balloons.
In Europe, researchers are exploring the use of Ovabloc, silastic plugs that block the fallopian tubes, as a possible method of reversible female sterilization. Using a hysteroscope (a device used for direct visual examination of the uterine cavity), liquid silicone is placed in the fallopian tubes, where it hardens within five minutes . Studies are under way in the Netherlands, where some 90 plug insertions are performed annually. No pregnancies have been reported to date, although 8 percent of women experienced migration of the plugs away from the original placement.4
Also, researchers in Sweden have investigated P-block, a water-based gel that is inserted by hysteroscope and expands to block the fallopian tubes. There have been problems with expulsion, and pregnancy rates are high. Another method, the Hamou tubal plug, blocks the tubes with a nylon or plastic thread. Again, there have been problems with plugs migrating or breaking.
Researchers also are exploring the use of an intrauterine balloon, which would be used to deliver the tissue adhesives into the fallopian tubes, and technologies now used to help couples conceive -- methods that clean debris from the fallopian tubes, break down adhesions or place egg, sperm or embryos in the tube -- that might be used to deliver devices or drugs to prevent conception.
Male methods
While female methods involve placement of chemicals or other substances to block the fallopian tubes and form a barrier to conception, male methods involve the injection of chemicals or other substances directly into the vasa deferentia in the scrotum, which transport sperm from the testicles. The chemicals cause scarring that blocks the vas or form plugs, which become a mechanical barrier to prevent passage of sperm. Researchers are looking for new male techniques that are less obtrusive than current procedures or may improve prospects for reversal.
One study involved 456 men in China who received a single injection of a carbolic acid mixture. Ten years after the injections, the azoospermia rate among study participants was 95.6 percent.5
Researchers also have explored injection of medical polyurethane (MPU) solution, which hardens to form plugs in the vas. Some 300,000 procedures have been performed in China, achieving a 98 percent azoospermia rate.6 A study of 12,000 men, conducted by the Sanxi Provincial People's Hospital in Taiyuan, found a 98 percent azoospermia rate after three years.7
In Indonesia, a WHO-supported study found high success rates in the use of silicone plugs to block the vas deferens. A small study of the efficacy of silicone plugs, conducted by WHO and AVSC International, is now under way in the Netherlands.
Currently, a 10-center study involving more than 3,500 men is under way to compare three methods of male nonsurgical sterilization: injections of polyurethane plugs or the chemical methylcyanoacrylate to occlude the vas and traditional ligation by no-scalpel vasectomy. Six months following the procedure, the azoospermia rates were 97 percent for men who had undergone no-scalpel vasectomy; 89 percent for chemical occlusion; and 68 percent for silicone plugs. At 24 months, the azoospermia rate was 98 to 99 percent for all groups. The study is being conducted by WHO and the State Family Planning Commission of China, with some funding from the United Nations Population Fund.8
-- Barbara Barnett
References
- Dusitsin N. Specifications for new technologies for female sterilization for use in developing countries. Int J Gynaecol Obstet 1995;51 (Suppl 1):S15-16; Wilson EW. The development of new technologies for female sterilization: conclusions and recommendations for research. Int J Gynaecol Obstet 1995;51(Suppl 1):S71-74.
- Janowitz B, Núñez J, Covington DL. Why women don't get sterilized: a follow-up of women in Honduras. Stud Fam Plann 1985;16(2):106-12.
- Sokal DC, Zipper J, Guzmán-Serani R. Cancer risk among women sterilized with transcervical quinacrine hydrochloride pellets. Fertil Steril 1995;64(2):325-34.
- Neuwirth RD. Update on transcervical sterilization. Int J Gynaecol Obstet 1995;51(Suppl 1):S23-28; World Health Organization. Transcervical sterilization methods. Progress in Human Reproductive Research 1995:36.
- Liu Z, Li S. Vasal sterilization in China. Contraception 1993;48:255-65.
- Liu, 260.
- Zhoa S-c. Vas deferens occlusion by percutaneous injection of polyurethane elastomer plugs: clinical experience and reversibility. Contraception 1990;41(5):453-59.
- Griffin PD. Methods for the regulation of male fertility. Annual Technical Report 1995. (Geneva: World Health Organization, 1995) 73-87.
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