REASERCH TRIANGLE PARK, NC — New findings from Family Health International (FHI) show that the amount of nonoxynol-9 (N-9) in a vaginal spermicidal gel may influence how well it prevents pregnancy. The form in which the N-9 is delivered, however, does not appear to have an influence.
In a clinical trial among more than 1,500 women at 14 sites throughout the United States, women who used a spermicidal gel containing a low dose of N-9 were about 1.5 times more likely to become pregnant than were women using either of two gels containing higher doses. But pregnancy rates did not differ significantly among women using a gel, film, or suppository containing equal doses of N-9. All doses used in the trial were comparable to those found in over-the-counter spermicides sold today.
Results of the study, supported by and conducted in collaboration with the National Institute of Child Health and Human Development, are reported in the March 2004 issue of the journal Obstetrics and Gynecology.
"We did show that the spermicidal gel with the lowest dose of N-9 was the least effective of the three gels tested," says Elizabeth G. Raymond, MD, MPH, an associate medical director at FHI and principal investigator of the study, "but we believe it is still more effective than using no contraceptive method at all."
Neck Graphic New Tee Short Fashion Sleeve Round Vaginal spermicides containing N-9 have been available without a prescription for more than 50 years in the United States, but knowledge about exactly how well different products prevent pregnancy has been limited. In 1995, the U.S. Food and Drug Administration proposed a ruling that more data on the effectiveness of specific products are needed to keep them on the market.
During the trial, 1,536 women ages 18 to 40 years old were randomly assigned to receive one of the following five spermicides: a gel containing 52.5 mg of N-9 per dose; a gel, film, or suppository containing 100 mg of N-9 per dose; or a gel containing 150 mg of N-9 per dose. The women were then asked to use the spermicides as their only method of contraception for six months, although they could use emergency contraception as backup if needed.
Data collected during the trial, from June 1998 to August 2002, indicated that the risks of vaginal conditions or urinary tract infections were similar among all women, regardless of which spermicide they used. Furthermore, "the risks we found were not alarmingly high when compared with what might be expected among young U.S. women in general," says Dr. Raymond.
Results also showed similar rates of effectiveness for all three spermicidal forms containing 100 mg of N-9. But during typical use of the spermicidal gels, 22 percent of women using the lowest-dose gel became pregnant, while only 15.5 percent of women using the medium-dose gel and 14 percent of women using the highest-dose gel did. Overall pregnancy rates during typical use of all five spermicides ranged from 10 percent to 22 percent.
"Findings from this new study are consistent with prior evidence suggesting that spermicides are still only moderately effective when compared with other methods such as oral contraceptive pills, injectable contraceptives, and intrauterine devices," Dr. Raymond says. "Women who want to avoid pregnancy should consider this when deciding whether to use spermicides for contraception."
Source. Raymond EG, Chen PL, Luoto J, The Spermicide Trial Group. Contraceptive effectiveness and safety of five nonoxynol-9 spermicides: a randomized trial. Obstet Gynecol 2004;103(3):430-39.