Women’s rights groups seeking easier access to emergency contraception are pressuring U.S. regulators as they try to decide whether to approve a non-prescription “morning-after” pill.

The Food and Drug Administration last year denied a request by Barr Pharmaceuticals Inc. to sell the contraceptive, called Plan B, over the counter. That sparked a furor over whether the decision was based on scientific evidence or political considerations.

FDA officials cited a lack of information on whether girls under 16 could use the drug safely without a doctor’s input. That prompted Barr to refile its request that the pill be made be available without prescription to patients 16 and older.

Plan B reduces the chance of pregnancy if it is taken within 72 hours of unprotected sex. It contains higher doses of the hormone progestin than that in regular birth-control pills, and women are supposed to take two tablets 12 hours apart.

With an FDA decision expected next week, some women’s groups have been petitioning the agency for approval. A handful of protesters were arrested on Jan. 7 at the FDA’s Maryland headquarters when they tried to block the entrance.

Supporters argue that easier access to Plan B would reduce the number of abortions. Opponents counter that easier availability would promote promiscuity and sexually transmitted diseases, particularly among teenagers.

Barr, based in Woodcliff, New Jersey, offered a compromise in July and asked to sell the drug over the counter to women aged 16 and older who show proof of age. Younger patients would still need a doctor’s prescription.

Amy Allina, policy director at the National Women’s Health Network, said Barr’s request was already a “loss for young women” who need timely access to the pill to avoid abortions or having a child they cannot support.

“This is about preventing unintended pregnancy,” she said, adding that there was no scientific basis for the rejection.

Conservative lawmakers and others who oppose easier access argue that the pill could increase risky sexual behavior, including rape.

“We are at epidemic levels for sexually transmitted diseases. This would make it worse,” said Wendy Wright, senior policy director of the conservative group Concerned Women for America.

Opponents also argue that Plan B causes abortion - a charge supporters reject.

Plan B works by preventing implantation of the fertilized egg in a women’s uterus, an important distinction, supporters say, from the RU-486 abortion pill which dislodges the egg.

Steven Galson, acting director of the FDA’s drug division, has defended the agency’s first decision, despite a 23-4 vote from an FDA advisory panel in favor of over-the-counter sales.

A new research study published this month in the Journal of the American Medical Association has fueled the controversy, and some financial analysts have said it could favor Barr. The study of 2,117 women showed that emergency contraception does not influence the degree to which women have unprotected sex, researchers said.

Piper Jaffray analyst Deborah Knobelman recently upgraded Barr’s stock to “outperform,” citing the Plan B decision as one of several potentially positive events.

Emergency contraception is already available without a prescription from pharmacists in six states: Alaska, California, Hawaii, Maine, New Mexico and Washington.

Plan B is sold over the counter in more than 30 countries.