No one will ever accuse the U.S. Food and Drug Administration of making a snap decision on Depo-Provera. Used by 30 million women worldwide since it was introduced in the late '60s, the injectable contraceptive was entangled in medical and political controversy here for more than two decades before the agency finally approved it in October. This month, for the first time, U.S. women will be able to receive the drug as an officially approved birth control method. (It has been prescribed in this country for endometrial and renal cancers since the early '70s.) "It is as safe as any other hormonal or intrauterine contraceptive, and it increases the options for American women, "says Dr. Allan Rosenfield, 59, dean of the School of Public Health and a professor of obstetrics and gynecology at Columbia University in New York City. Dr. Rosen-field first observed Depo-Prover ah usefulness in Thailand, where he worked from 1967 to 1973 for the Population Council, an international family-planning organization. He expects the drug, which is administered as a. shot every three months, to play an important role in the U.S. too. He spoke with Chicago bureau chief Giovanna Breu.

What is Depo-Provera and how does it work?

Basically it's a synthetic compound similar to the female hormone progesterone. Injected into a woman's arm or buttock, it protects against pregnancy for three months by preventing ovulation.

How effective is it?

If you get your shot every three months, even a week or two late, it has a failure rate of less than 1 percent per year. This is better than the pill but slightly less effective than Norplant [an implanted but reversible contraceptive that lasts five years].

The relationship between the pill and breast cancer has been studied at length. Have similar studies been done with Depo-Provera?

Yes. We don't see an increase in breast cancer overall There does, however, appear to be a very slight rise in breast cancer among younger women. On the other hand Depo-Provera may, like the pill, protect against uterine and possibly ovarian cancers.

What are the major side effects of Depo-Provera?

Menstrual spotting and irregular bleeding, and occasionally heavy bleeding in the first few months of use. After a year, up to half the women slop having their period, often as long as they take the drug. So far as is known, this isn't harmful. There are also reports of symptoms including headaches, mood changes, dizziness and fatigue, but it's hard to be sure whether those are due to Depo-Provera. Finally, there is some weight gain, an average of 3 to 5 lbs.

Can Depo-Provera increase the risk of osteoporosis?

There may be some decrease in bone density—reversible when Depo-Provera is discontinued—but with data still coming in, we aren't sure.

Is there any basis for claims that Depo-Provera decreases sex drive?

The vast number of users report no change. A few said there was a decrease, but others reported a rise.

What about the fear that, because it is injectable, it can be administered to poor women or drug addicts against their will?

At least one judge has offered Norplant as a means to lighten a sentence where there were child-abuse issues. Some legislators have suggested that women on welfare be pressured to use Norplant after having an abortion. Most of the medical community strongly oppose any coercive use of Norplant or Depo-Provera.

Why choose Depo-Provera over other contraceptives?

Some women find it difficult to remember to lake a pill every day, or man need to get off it because in conjunction with smoking or high blood pressure it is thought to increase the risk of heart attacks or strokes for those over the age of 35. Others may not like the messiness of barrier methods. So a relatively painless injection four times a year could be attractive. And because it is easily reversible, it's a good alternative to sterilization for younger women.

Can you get pregnant when you stop using Depo-Provera?

It usually takes longer than it does after you stop the pill or Norplant. But by the end of 18 months, women will get pregnant at the same rate.

What would you suggest for teens?

Depo-Provera may not be the right method, because a teen might not want to wait up to 18 months when she's ready to get pregnant. I would recommend Norplant, whose effectiveness ends when the implants are removed. But if I had my druthers, I'd drape teens from their heads to their toes in a full-body condom. They need protection against sexually transmitted diseases and AIDS.

What will Depo-Provera cost?

Reportedly about the same as pills.

What other kinds of contraceptives need to be developed?

I wish there was an equally good injection for men.