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New Spermicide Matches Nonoxynol-9 in Efficacy


 

LA JOLLA, CALIF. — The new spermicidal microbicide BufferGel, when used with a diaphragm, is a safe, acceptable contraceptive with efficacy that is noninferior to the Gynol II-diaphragm combination, according to a phase III multicenter study.

“These important findings demonstrate that a new spermicide and potential microbicide works as well as the currently marketed nonoxynol-9-based product,” Dr. Kurt T. Barnhart said in an interview. “The advantages of this new product, the first nonsurfactant spermicide demonstrated to work in decades, is that it is potentially safer than N-9 and may also prevent HIV transmission,” said Dr. Barnhart, who is director of clinical research for the department of obstetrics and gynecology at the University of Pennsylvania in Philadelphia.

Whereas N-9 is a surfactant that indiscriminately disrupts epithelial cell membranes and kills sperm before they can enter the uterus, BufferGel is a nondetergent agent that keeps the pH in the vagina acidic instead of raising it to neutrality when sperm are introduced, Dr. Barnhart said at the annual meeting of the Association of Reproductive Health Professionals.

“By keeping those natural defenses acidic, BufferGel is toxic to both sperm and some microbes, including HIV, though the phase II-III HIV arm of the trial is still underway in Africa,” he explained.

These new findings emerged from an 11-center noninferiority trial stemming from the hypothesis that BufferGel is noninferior to Gynol II when both compounds are used with a diaphragm, with noninferiority being defined as within 6% of each other in terms of contraceptive efficacy.

This was a two-part trial: Study 1 was a double-blind, randomized, direct comparison of the two preparations. A total of 621 women used BufferGel and 300 received Gynol II. After completing six cycles, they could elect to continue for an additional six cycles as part of an open-label BufferGel study (study 2), and 234 did so. Of those, 63 discontinued before 6 months elapsed.

Study 1 showed the two compounds to be comparable in virtually all respects. “All the differences favor BufferGel, but those differences were within 6% of each other, so we can say these two products are noninferior to each other,” said Dr. Barnhart. About the same percentage (3%) in each group thought adverse events warranted discontinuation, Dr. Barnhart said.

At cycle six, 68% of BufferGel users and 70% of Gynol II users said they would definitely or probably use the product if available, while 54% of BufferGel users and 57% of Gynol II users preferred the system to condoms.

BufferGel's typical use pregnancy rate was 10% in this study sponsored by the National Institute of Child Health and Development Clinical Trials Network.

'Differences were within 6% …, so we can say these two products are noninferior to each other.' DR. BARNHART

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