The study, published in this month's Obstetrics & Gynecology, helped the Food and Drug Administration decide that the pill -- also known as Plan B or the morning-after pill -- could be purchased over the counter by women of any age. In December, however, the Department of Health and Human Services (HHS) overruled that decision.

"This study confirms findings from two other studies that teens are able to understand (emergency contraception) labeling in order to use it safely and effectively," said Megan L. Kavanaugh, a senior research associate at the Guttmacher Institute in New York, in an email to Reuters Health.

Kavanaugh, who was not involved with the new study, added that these findings indicate "that there is no scientific basis for the continued age restriction on over-the-counter access to Plan B One Step."

Researchers at the University of California, San Francisco, led by Dr. Tina Raine, tracked girls between the ages of 13 and 17 who came into health clinics in five cities for the pill.

The pill contains the hormone progestin, which cuts the risk of pregnancy after unprotected sex by stopping the ovaries from releasing an egg.

For the new study, the girls read the information on the product's box and then told the study's staff whether or not they still wanted to use it.

The girls who still wanted to use the drug filled out surveys on why they wanted to use it and about their medical history. From that information, the study's staff determined whether the drug was appropriate for the girls.

Of the 340 girls who earned $10 for participating in the study, the staff decided 311 -- about 92 percent -- correctly used criteria to choose to use or not use the drug based on their answers.

Thirteen of those girls decided not to use the drug because the window during which it would be most effective had passed. The study's staff gave the 298 girls who correctly chose to use the drug the single-dose pill. Of those, 274 used the drug correctly.

There was no correlation between the correct decision to use the drug -- or use it correctly -- and any specific age.

"There are no medical concerns. That's why the FDA approved it for them. The concern is more a social, political concern about adolescents having access to these contraceptives," said Cynthia Harper, one of the study's authors and a professor in the Department of Obstetrics, Gynecology & Reproductive Sciences at UCSF.

The study did have limitations, including self-selection, because girls who choose not to use emergency contraception may be different than those who do.

The new study and its authors were funded by a grant from Teva Pharmaceuticals -- the morning-after pill's maker. Raine and Harper's salaries -- along with two of the study's staff -- were supported by the grant, and two of the authors are Teva employees. The company also covered Raine's travel to present the information to the FDA in 2007 and 2010.

HHS could not be reached for comment by deadline. SOURCE: Obstetrics & Gynecology, online March 5, 2012.

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