A clinical trial of nonoxynol-9 for preventing gonococcal and chlamydial infections.

A randomized, double-blind, placebo-controlled trial was conducted to evaluate the spermicidal agent nonoxynol-9 as prophylaxis for cervical infections caused by Chlamydia trachomatis and Neisseria gonorrhoeae. Eight hundred eighteen women were recruited from a sexually transmitted disease clinic. Only subjects who were using reliable birth control methods (oral contraceptives, intrauterine device, or sterilization) were eligible. Subjects were randomly assigned to use either a commercially available spermicidal agent containing nonoxynol-9 or a placebo preparation. Subjects were followed up for six months; specimens were collected monthly for culture of the two pathogens. Women assigned to the nonoxynol-9 group were less likely to become infected with N. gonorrhoeae (relative rate, 0.75; 90% confidence limits, 0.58 and 0.96) and C. trachomatis (relative rate, 0.79; 90% confidence limits, 0.64 and 0.97). Among women who used their assigned gel for the majority of coital episodes, a stronger protective effect was observed.