Opill is known as a “mini pill” because it contains only one hormone, progestin, in contrast to “combination” pills, which contain both progestin and estrogen. A company that makes a combination pill, Cadence Health, has also been in discussions with the F.D.A. about applying for over-the-counter status.

Dr. Daniel Grossman, a professor of obstetrics, gynecology and reproductive sciences at the University of California, San Francisco, spoke in support of the over-the-counter effort in the advisory committee’s hearing on Tuesday. He said in an interview that both types of pills were safe and about 93 percent effective in preventing pregnancy with typical use.

Combination pills have been more popular in the United States, but that may be because progestin-only pills, which are widely used in Europe, have not been marketed much in this country, he said.

HRA Pharma, which was purchased last year by Perrigo, a Dublin-based maker of over-the-counter pharmaceuticals, already sells a nonprescription progestin-only pill in the United Kingdom.