There is something new in birth control--in the lab if not on store shelves

November 25, 1990|By Judy Berlfein

Birth control seems stuck in the '60s. On the surface, it appears that the contraceptive revolution that ushered in the birth control pill has come to a screeching halt. For almost three decades, women and men have had to be content with the same limited choices.

Can we hope for more options in the immediate future?

"Don't hold your breath," responded pharmacologist Gabriel Bialy, chief of the contraceptive development branch at the National Institute of Child Health and Human Development in Bethesda.

But while the picture is bleak for the consumer searching the pharmacy shelves, a look behind laboratory doors reveals some long-term prospects. A small number of scientists are investigating a full array of potential contraceptives, all at various stages of development.

Most of these products rely on the basic building blocks of the oral contraceptive, estrogen and progestin. These steroid hormones are released in a cyclical fashion naturally by the ovaries. Birth control pills' continuous flow of hormones inhibits ovulation through a feedback loop operation.

Under normal circumstances, the hypothalamus conducts a complex symphony of hormones, orchestrating first the release of gonadotropin releasing hormone (GnRH). This signals the pituitary to secrete luteinizing hormone (LH), which in turn facilitates ovulation and coordinates release of the steroids estrogen and progestin from the ovaries.

In contrast, a woman taking birth control pills maintains a steady circulation of estrogen and progestin. The hypothalamus senses this constant presence and shuts off GnRH production in reaction. Without this key player, LH is also inhibited, and ovulation ceases to take place.

While scientists capitalized on this manipulation of hormones to develop the pill, today they are going beyond the one-a-day concept, packing the hormones into an array of alternative delivery systems. Researchers eventually hope to offer implants, injectables and vaginal rings. All of these techniques release steroid hormones in a slow and steady dose over various lengths of time.

Norplant, one of the most promising methods, is now available in 15 countries -- including Finland, Sweden and Czechoslovakia -- and will soon complete clinical trials in the United States. The device consists of six match-stick-size capsules, filled with progestin and inserted with a tiny incision under a woman's arm.

After the simple, 15-minute procedure, the woman remains protected from pregnancy for five years. If for any reason she wishes to discontinue use, a practitioner can remove the capsules.

Unlike the birth control pill, Norplant and many of the other long-acting contraceptives contain a single hormone, progestin. Working alone, without the accompanying estrogen, progestin will still block GnRH, thus inhibiting ovulation. The hormone also causes thickening of the cervical mucus, which prevents fertilization.

Dr. David Archer, clinical investigator in the Contraceptiv Research and Development Program (CONRAD) at Eastern Virginia Medical School in Norfolk, Va., said scientists excluded estrogen from the formulation to eliminate the cardiovascular and blood-clotting risks of the birth control pill. However, this non-estrogen package comes with its own trade-offs. The single-steroid contraceptives cause abnormal bleeding in many women during the first year. Some spot continuously throughout their cycle, while others lose their periods altogether.

According to some, this annoying side effect may place damper on the marketing potential of progestin-only contraceptives. Dr. Daniel Mishell, chairman of the department of obstetrics and gynecology at Los Angeles County/University of Southern California Medical Center, has been running Norplant clinical trials. He predicted that Norplant would never achieve the pill's popularity in the United States because unpredictable bleeding patterns would scare away potential users.

A few variations on the implant theme are also under scrutiny. Scientists at Family Health International in Research Triangle, N.C., have created an injectable formulation: They encased a progestin in biodegradable microspheres. Over a 90-day period the smallest spheres dissolve first, releasing the hormone into the bloodstream, with the larger ones progressively disintegrating over time.

For those wary of needles or incisions, researchers have an additional hormone-based option: The flexible, doughnut-shaped, vaginal ring can be formulated with both estrogen and progestin. Women place the one-size-fits-all ring on the cervix like a diaphragm. This localized form of birth control pill remains in place for three weeks and is then removed during the menstrual cycle. The hormone supply lasts four to six months.

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