Collagen sponge as vaginal contraceptive barrier: critical summary of seven years of research.

Extensive testing of collagen sponge as a vaginal contraceptive (mechanical and chemical) showed that the original expectations regarding the safety, convenience, and efficacy were not met. The collagen sponge was tested both as a cylinder and as a diaphragm and used as such or impregnated with spermicidal detergent or with zinc salt. The collagen sponge must be larger than 6 cm in diameter in order to serve as a mechanical barrier that will not be dislodged during physical activity. This creates problems with the ease of insertion and with the partners' awareness of the barrier. When the collagen sponge containing ejaculate is left in the vagina greater than 48 hours, it develops an offensive odor. The original acidity of the collagen sponge (pH 3.5, 0.1 mol/L) is soon neutralized by the large volume of alkaline vaginal secretions. In vitro studies showed that up to 10 mg of nonoxynol 9 per milliliter of growth medium did not inhibit the growth of Staphylococcus aureus. These effects, as well as the large surface area of the resilient sponge, present a potential risk for growing staphylococci within the collagen sponge. The capacity of the collagen sponge to absorb a large volume of cervical and vaginal fluid produced two symptoms that were annoying to the volunteers: an awareness of either vaginal dryness during intercourse or, conversely, saturation of the sponge from the vagina. Postcoital studies showed viable spermatozoa in the cervical mucus in 25% of the tests with the nonmedicated cylindrical sponge but in only 6% of tests with the sponge containing nonoxynol 9. The results of clinical trials conducted at four centers support the view that collagen sponge as a vaginal contraceptive barrier method is inconvenient to both partners, not effective enough to compete with present methods of vaginal contraception, and possibly might be unsafe because of the capacity to grow bacteria. Despite the negative end result of this goal-oriented research, we believe that our studies have contributed to a better understanding of vaginal physiologic features, the safety and effectiveness of spermicidal detergents, and the mechanisms of vaginal malodor. Although the acceptability study showed some advantages of the collagen sponge over the rubber diaphragm, the overall acceptability of the collagen sponge diaphragm was no better than that of the rubber diaphragm. For all these reasons, including the possible risk of an increased incidence of toxic shock syndrome, we have discontinued further testing of either type of collagen sponge as a vaginal barrier method.