Emergency Contraception Safe for Use in Teenage Girls

Melissa Schorr

November 18, 2003

Nov. 18, 2003 (San Francisco) — Emergency contraception was safe and well tolerated by teenage girls, a population in which the drug has not previously been tested, researchers reported here Monday at the annual meeting of the American Public Health Association.

"All adolescents took the medications safely," study author Cynthia Harper, PhD, an assistant professor of obstetrics and gynecology at the University of California at San Francisco, told Medscape in an interview.

Dr. Harper and colleagues conducted two tests to study the safety and pharmacokinetics of the emergency contraceptive levonorgestrel, marketed as Plan B.

Before its release in 1999, the drug was tested primarily in women older than 18 years in studies conducted by the World Health Organization (WHO), Dr. Harper noted.

"We didn't have any data in young users," she said. "Obviously, a lot of teenagers could be using this because of the high unintended pregnancy rate."

In general, "the [Food and Drug Administration] has put a lot of emphasis on getting pediatric data," Dr. Harper pointed out. "We think it's just as important to study the use of contraception" in this population.

The study was conducted on 55 teenage girls aged 13 to 16 years who were not pregnant and whose parents gave permission for them to participate.

The girls were administered 0.75 mg of the drug orally, and instructed to take the second tablet 12 hours later. The researchers also studied blood samples from 22 of the girls up to three days after taking the pill, comparing the results with adult patients. They assayed plasma samples at 0, 0.5, 1.0, 1.25, 1.5, 1.75, 2, 4, 8, 12, 24, and 72 hours.

Dr. Harper reported that 98% of the teenage girls used the drug properly and returned to their menstrual period in the same timeframe as the adult women did.

While the teens reported more adverse effects such as nausea, dizziness, fatigue, and headaches than seen in the WHO study, that difference disappeared when they were compared with the adult population from the Western Hemisphere. No serious adverse events were reported.

The pharmacokinetics study found that the teens tended to clear the drug from their system faster than adult women did. "The adults had a higher exposure, the adolescents cleared it faster," Dr. Harper said. She attributed this difference to a subset of Latina adolescents who had higher total plasma clearance.

This may be due to a decrease in protein binding, or possibly a decrease in bioavailability, Dr. Harper said. When controlling for ethnicity and body weight, the difference between the teen girls and adult women was not significant.

At the levels the drug is administered, this difference did not seem to affect efficacy, Dr. Harper said. "It's unlikely to be clinically significant because emergency contraception is prescribed with such a high amount of levonorgestrel."

"I think this is reassuring to know that adolescents can take emergency contraception and have no adverse effects," noted Ellen Mitchell, PhD, a research associate at Ipas, a reproductive research and evaluation group based in Chapel Hill, North Carolina, who commented on the poster presentation. "There has been an assumption they will have more side effects."

The study was funded with grants from the William and Flora Hewlett Foundation, the Women's Capital Corporation, and the General Clinical Research Center at San Francisco General Hospital in California.

APHA 131st Annual Meeting: Poster Session 3070.0, Board 8. Presented Nov. 17, 2003.

Reviewed by Gary D. Vogin, MD


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: