Since Accutane began selling in 1982, the FDA has reports of well over 2,000 pregnancies among users. The vast majority ended in abortion or miscarriage, but the FDA counts more than 160 babies born with drug-caused defects.

The Food and Drug Administration enacted unprecedented curbs Friday in trying to keep Accutane and its generic competitors on the market while ensuring that women who use the risky pills don't get pregnant. Critics see it as the drug's last chance, after two decades of safety warnings and other restrictions failed to end Accutane-damaged pregnancies.

"This is a system that has been long in the works and many would say is long overdue," acknowledged Dr. Sandra Kweder, FDA's deputy drug chief. "The responsibility for ensuring that fetuses are not exposed to this medicine is enormous, and is shared by everyone" who takes, prescribes or sells it.

Severe Brain and Heart Defects

If a woman becomes pregnant while taking the acne drug, her baby can suffer severe brain and heart defects, mental retardation and other abnormalities, even if the mother took only a small dose for a short period. That's a risk for 30 days after stopping the drug, too.

Under the program, every patient -- men and women -- must enroll in the iPLEDGE computerized registry starting Dec. 31 to receive Accutane or generic versions of the drug isotretinoin.

Doctors must register, too, if they wish to continue prescribing the pills. Drugstores and wholesalers also must register in order for the pills' manufacturers to ship them any supplies.

How does the program work?

All patients seeking a prescription must sign a document informing them of Accutane's risks, including the possibility that it contributes to depression or suicidal thoughts -- a warning on the drug's label that FDA also strengthened Friday.

Patients must agree to monthly doctor visits for refills and not to share the pills with anyone. Then the doctor registers each patient into the iPLEDGE database, giving him or her a special identifying code number, and writes the prescription.

For Severe Acne Only

But for women of childbearing age, there are some additional steps:

The pharmacist must check the computer database before filling a prescription to ensure that patients followed all these rules. Accutane manufacturer Hoffman-La Roche and generic manufacturers will monitor drugstores and wholesalers, and are supposed to cut off violators' sales supplies.

Accutane is supposed to be used for severe acne only, but it is widely acknowledged to be prescribed for more minor cases. The FDA estimates that 100,000 prescriptions are filled each month.

Voluntary Restrictions Did Not Work

"We are very happy that this has happened and wish it had been done years ago," said Dr. Nancy Green, medical director of the March of Dimes.

But the organization, which fights birth defects, will be watching closely to see if the program stops fetal exposure to the risky pill -- something tough to do considering the acne drug's chief market is young people, and that half of all US pregnancies are unplanned.

"If it looks like this is a leaky system despite FDA's efforts to really step it up, we may very well call for it to be taken off the market," Green warned.

Since Accutane began selling in 1982, the FDA has reports of well over 2,000 pregnancies among users. The vast majority ended in abortion or miscarriage, but the FDA counts more than 160 babies born with drug-caused defects. Critics note there likely were many more pregnancies because doctors haven't been required to report Accutane-linked pregnancies. Friday's new rules mandate that they do.

FDA first attempted to tighten Accutane access in 2001, but the restrictions were largely voluntary and didn't work: The FDA counted 120 pregnancies among the drug's users in the first year of that program, just seven fewer than in the previous year even though overall prescriptions dropped by 23 percent.

The registry actually opens on Aug. 22, giving users extra time to learn how it works before the provisions become mandatory at year's end. On that date, patients may enroll at http://www.ipledgeprogram.com or by phone at 1-866-495-0654.