The results of a preliminary study suggest that administration of emergency contraception through the vagina could be an effective alternative to oral administration - and may reduce the levels of nausea and vomiting.

Dr. Eliran Mor of the University of Southern California Medical Center in Los Angeles and colleagues found that administering twice the standard dose of two emergency contraceptive regimens resulted in the same transient reduction in hormone levels that occurred when standard doses were given orally.

Now, much larger studies are required to determine whether the findings will translate to clinical effectiveness, said Mor. At least for the inhibition of gonadotropin hormones, “the vaginal route seems to be as effective,” he said.

Nausea and vomiting are common side effects of emergency contraception regimens, Mor and his team note in their report in the medical journal Fertility and Sterility.

Half of women who take a regimen that containing levonorgestrel and ethinyl E2, the Yuzpe regimen, report nausea, and more than one in five vomit, they point out. A newer but less widely used regimen that uses levonorgestrel only, known as Plan B, is less likely to cause vomiting, but still makes about one in four women nauseous.

Emergency contraception is believed to suppress ovulation by inhibiting gonadotropins. So Mor and colleagues conducted the current study to compare the effect of both the Yuzpe regimen and Plan B, given orally and vaginally, on blood levels of gonadotropins.

Women in the study were given double the standard oral dose of one of the regimens vaginally, and then were given the standard dose of the same regimen orally after a one-week washout period.

Five women received the Yuzpe regimen and four were given Plan B.

Women administered the vaginal hormones themselves, after which they were asked to sit for four hours and restrict their physical activity for another four hours.

Levels of gonadotropin and other hormones were reduced similarly with all four regimens, and returned to normal within 24 hours, the researchers found.

There was no significant difference in gonadotropin suppression between the Yuzpe regimen and Plan B. “This, along with the recent finding that Plan B is more efficacious in preventing unwanted pregnancies than the Yuzpe regimen, suggests that the role played by (ethinyl E2) in emergency contraception may be a redundant one,” they note.

Mor noted that vaginal administration delivers hormones directly to where they are needed and is also known to be an effective route of hormone delivery, so it is possible lower doses of emergency contraception could be effective if delivered vaginally.

“In theory, the vaginal route should be perhaps beneficial or preferable,” he said.

SOURCE: Fertility and Sterility, July 2005.