MORRISTOWN, N.J. — Watson Pharmaceuticals Inc. plans to launch ella, an oral emergency contraceptive, in the fourth quarter.

The drug maker said late Friday that the announcement follows the approval of ella (ulipristal acetate) by the Food and Drug Administration as safe and effective in preventing unintended pregnancy for up to 120 hours, or five days, after unprotected intercourse or contraceptive failure.

Ella was developed by HRA Pharma specifically for emergency contraception and is not intended for routine contraceptive use, according to Watson. The company said it will market ella in the United States under an exclusive distribution agreement announced earlier this year. Ulipristal acetate has been available in Europe since October 2009, where it’s marketed by HRA Pharma as ellaOne.

A progesterone agonist/antagonist emergency contraceptive, ella is proven effective in helping prevent pregnancies at various stages of the menstrual cycle, including just before ovulation — the time in a woman’s cycle when the probability of pregnancy is highest, according to Watson. Ella is effective in delaying ovulation for up to five days, which is key because sperm can survive for up to five days in the genital tract, the company said.

Currently available over-the-counter levonorgestrel-based emergency contraceptives are indicated for use within 72 hours of unprotected intercourse or contraceptive failure, and their effectiveness in preventing pregnancy decreases just prior to ovulation, Watson reported.

"Ella is an important new contraceptive option for U.S. women, and its unique efficacy profile will give women an additional therapeutic alternative for preventing unintended pregnancy," Fred Wilkinson, executive vice president of Watson’s Global Brands division. "Beginning later this year, Watson will be offering women a novel emergency contraceptive that represents a logical, therapeutic complement to NextChoice, our generic levonorgestrel-based emergency contraceptive."

The approval of ella is based on data from clinical studies that enrolled more than 2,600 women, Watson said. Among women who were administered ella within 72 hours of unprotected intercourse, the overall pregnancy rate was 1.9%, significantly lower than the anticipated pregnancy rate (5.6%). Among women who were administered ella 48 to 120 hours after unprotected intercourse, the overall pregnancy rate was 2.2%, much lower than the expected pregnancy rate (5.5%).

Ella will be available to U.S. women by prescription beginning in the fourth quarter and will be marketed by Watson’s Global Brands division. The company said recent partnerships with HRA Pharma, the Population Council and Columbia Laboratories have enabled it to expand its branded offerings and pipeline in women’s health to include infertility, emergency contraception, long-term contraception and pre-term birth.