Laboratory and clinical testing of an intravaginal contraceptive collagen sponge

Abstract

The efficacy of collagen sponge (CS) used as intravaginal contraception barrier depends largely on the continuous retention of CS in the upper vault of the vagina, prompt absorption of ejaculate into CS and inactivation of sperm by acidity of the sponge. All three factors were tested in in vitro studies, and retention was also evaluated in human volunteers. Retention seems to depend on adequate resilience of the CS. This can be controlled by the degree of crosslinking of collagen fibers. With adequate resilience the expulsion rate, originally 33%, was reduced to 2.5%. Our tests were conducted by 30 volunteers who tested eight types of CS in a total of 213 insertions. The rate of fluid absorption by the CS could be significantly increased by treating the sponge with a surfactant, such as Triton X-100 (0.1%). It was found that prewetted sponge absorbs fluid instantaneously; thus, modification of CS with surfactant is not necessary. CSs were equilibrated to various pHs (4 to 7). Extracts from these were applied to fresh human spermatozoa to test the effects on sperm motility. At pH 5.0 the motility stopped after 4 min. while at pH 7.0 the cells were still active after 30 min. observation. This is one of the reasons why CSs used as contraceptive should have acidity around 5.0. The various methods of insertion and removal of CS were tested by five volunteers for 5 consecutive days. Both digital and applicator insertion were found acceptable. Removal of CS was facilitated by a loop or strand of umbilical tape fixed to the CS.