Effects of multiple applications of benzalkonium chloride and nonoxynol 9 on the vaginal epithelium in the pigtailed macaque (Macaca nemestrina)

OBJECTIVE: Safe and effective vaginally applied microbicides could help to control the continuing spread of sexually transmitted diseases. STUDY DESIGN: This study used nonhuman primates to test the effects of mult iple applications of nonoxynol 9, benzalkonium chloride, or a combination o n vaginal flora and lower reproductive tract tissues. Fourteen monkeys (Mac aca nemestrina) received daily vaginal applications of nonoxynol 9, benzalk onium chloride, or both for 3 to 4 days. Vaginal microflora and colposcopic observations were made at baseline and during and after completion of trea tments. Cervical biopsy specimens were collected from a subset of animals. RESULTS: Cervical erythema and vaginal erythema were observed in all 3 trea tment groups. Cervical papillae and epithelial disruption were present in b oth the nonoxynol 9 and the nonoxynol 9 plus benzalkonium chloride groups. Vaginal epithelial disruption was noted in both the benzalkonium chloride a nd the nonoxynol 9 plus benzalkonium chloride groups. Cervical biopsy speci mens from each group revealed acute inflammatory infiltrates with occasiona l plasma cells and lymphoid follicles. Detection of most microorganisms, in cluding viridans streptococci, decreased in the benzalkonium chloride and t he nonoxynol 9 plus benzalkonium chloride groups. Detection of Lactobacillu s species decreased in the benzalkonium chloride group. All microflora leve ls recovered after several days without microbicide use. CONCLUSIONS: Although nonoxynol 9 is currently the only microbicide approve d for use as a spermicide in the United States, its repeated use may be det rimental to the epithelial tissues of the female reproductive tract. Benzal konium chloride, currently approved for use in other countries, not only ma y damage epithelial tissues but also appears to reduce the population of po tentially protective Lactobacillus species in the vagina.