Wyeth

(WYE)

said Wednesday that federal regulators have delayed approving an experimental oral contraceptive that would eliminate menstrual periods.

Wyeth said the Food and Drug Administration granted conditional approval for the drug Lybrel, asking the Madison, N.J., company to send additional data regarding manufacturing methods and more information about clinical trial results that Wyeth had already filed with the agency.

The FDA will convene a panel of contraception experts to review Lybrel, the first oral contraceptive designed to eliminate periods. This committee will look at pregnancy rates among clinical-trial participants, bleeding patterns and the rates of discontinuation by women being tested, Wyeth said.

"Wyeth is confident that we can address the questions raised by the FDA, and we expect to move toward the launch of Lybrel," says Dr. Gary Stiles, executive vice president and chief medical officer for Wyeth's prescription drug division.

Barr Pharmaceuticals

(BRL)

sells Seasonale, an oral contraceptive that reduces the number of menstrual periods to four from 13.

Next month, Barr is expected to begin marketing Seasonique, which also enables quarterly menstrual periods. Both contraceptives experienced several delays at the FDA.

Lybrel contains two drugs, ethinyl estradiol and levonorgestrel, which are also used in Seasonale and Seasonique, but at different doses. These two drugs represent "a well-studied combination," Wyeth said.

Lybrel will be taken daily. Seasonique requires women to take a pill combining levonorgestrel and ethinyl estradiol for 84 consecutive days, followed by seven days of a separate ethinyl estradiol pill. Women taking Seasonale take the combination pill for 84 days, followed by a placebo for seven days.

Wyeth's announcement, which came about an hour before markets closed, didn't appear to affect the company's stock, which closed at $43.08, up 67 cents, or 1.6%.