HEALTH : Updating Birth Control : Looking to the Future, Researchers Examine Effects of New Methods
Birth control research moves slowly, but it is moving, researchers say.
Among the technologies working their way through the investigational pipeline are:
Norplant: An implantable contraceptive that inhibits ovulation and also thickens cervical mucous, impeding sperm penetration. Six match-size silastic capsules are implanted in the upper arm and release the ovulation-inhibiting hormone levonorgestrel over a period of five years.
The Population Council, the New York-based nonprofit organization that developed Norplant, filed for FDA marketing approval last August, but has not yet received it, spokeswoman Sandra Waldman said.
A potential drawback: A change in bleeding, including prolonged menstruation or “breakthrough” bleeding, said Dr. Donna Shoupe, a USC assistant professor of obstetrics and gynecology who’s studied Norplant.
Expected effectiveness: 97 % -99% .
RU-486: Perhaps the most controversial technique under study in the United States, RU-486 is manufacturer’s shorthand for a drug that interrupts pregnancy in early stages. In France, it was withdrawn from the market in October, 1988, after a campaign by pro-life advocates. Two days later, however, the government ordered the drug back on the market.
A so-called anti-progestin, RU-486 works by “blocking the effects of progesterone, the hormone that supports pregnancy,” said Dr. David A. Grimes, a professor of obstetrics/gynecology and preventive medicine who’s studying the drug at USC. In the absence of progesterone, the lining of the uterus breaks down as it would in a normal menstrual cycle.
In the last four years, 13 different regimens have been tested on 300 women in USC studies, Grimes said. Most promising: a single 600-milligram dose that interrupted pregnancy 90% of the time in 50 women studied.
Taken within two weeks of a missed menstrual period, the drug is 80% effective, according to a new report by Washington’s nonprofit Population Crisis Committee, and even more so when combined with synthetic prostaglandins. Possible side effects include hemorrhage and incomplete or failed abortion.
Expected effectiveness: 95%.
Nonscalpel Vasectomy: Under study by the Population Council and VasTech Medical Products Inc., of New Brunswick, N.J., nonscalpel vasectomy promises almost immediate recovery. After a local anesthetic is administered, scrotal skin is punctured with a Vasocclude, a device much like a stapler with preloaded clips, and the device is maneuvered near the vas deferens or spermatic duct, which is sealed off by a clip.
Clinical studies are scheduled to start this year.
Expected effectiveness: 99%.
Plug Sterilization: In this potentially reversible male sterilization procedure, two tiny puncture holes are made in each vas deferens, then two silicone plugs are inserted into the ducts. A tiny space between the two acts as a trap for sperm that may have gotten past the first plug.
“The vas is hardly damaged,” said Dr. Lourens Zaneveld , a professor of obstetrics and gynecology at Chicago’s Rush University. “When the plugs are removed, a small suture recloses the duct and the hole closes almost immediately.”
Preliminary clinical studies, under way here and in South America, showed a third of the men were sterile but in two-thirds, some sperm still passed by the plugs.
Expected effectiveness: 99% as contraceptive; 90% reversibility.
Anti-Sperm Vaccine: Human studies are expected to begin this year or next for a vaccine that attacks sperm and reduces their “fertilizability,” said Northwestern researcher Dr. Gerald Zatuchni , a professor of obstetrics and gynecology at Northwestern University in Chicago, Ill. First, an enzyme called lactic dehydrogenase is extracted from the sperm and injected into his partner. She, in turn, develops antibodies that attack the sperm, reducing motility and ability to fertilize eggs.
Expected effectiveness: 90%.
Injectables for Women: A biodegradable microcapsule of norethindrone, the same synthetic hormone found in most oral contraceptives, is injected into the buttocks, allowing for slow release of the hormone. Farthest along in clinical trials is a 90-day capsule; 30-day and 6-month systems are also being developed, said Zatuchni.
Expected effectiveness: 99%.
Injectables for Men: Periodic injections of a synthetic version of the hormone testosterone may reduce sperm counts to zero or other safe levels, researchers say. Testosterone inhibits sperm production much like oral contraceptives inhibit ovulation, said Dr. C. Alvin Paulsen, a researcher and professor at the University of Washington.
Other researchers, including Dr. Ronald S. Swerdloff, director of the UCLA Population Research Center and professor of medicine at Harbor-UCLA Medical Center in Torrance, are studying injections of testosterone combined with other substances that together “turn off” the sperm production system.
Expected effectiveness: Unknown.
Female Condoms: “When people first look at a female condom, they’re not too impressed,” said USC’s Shoupe, one of several researchers investigating various types of female condoms, also called intravaginal pouches. The one she’s studying looks like a plastic tube with a ring at each end. The upper ring is inserted like a diaphragm to prevent sperm passage while the other is positioned near the vaginal opening. Prelubricated with the spermicide nonoxynol-9, such condoms may help prevent the spread of sexually transmitted diseases, researchers say.
Expected effectiveness: 88%-96%.
