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

Abstract

Safe and effective vaginally applied microbicides could help to control the continuing spread of sexually transmitted diseases. This study used nonhuman primates to test the effects of multiple applications of nonoxynol 9, benzalkonium chloride, or a combination on vaginal flora and lower reproductive tract tissues. Fourteen monkeys (Macaca nemestrina) received daily vaginal applications of nonoxynol 9, benzalkonium chloride, or both for 3 to 4 days. Vaginal microflora and colposcopic observations were made at baseline and during and after completion of treatments. Cervical biopsy specimens were collected from a subset of animals. Cervical erythema and vaginal erythema were observed in all 3 treatment groups. Cervical papillae and epithelial disruption were present in both the nonoxynol 9 and the nonoxynol 9 plus benzalkonium chloride groups. Vaginal epithelial disruption was noted in both the benzalkonium chloride and the nonoxynol 9 plus benzalkonium chloride groups. Cervical biopsy specimens from each group revealed acute inflammatory infiltrates with occasional plasma cells and lymphoid follicles. Detection of most microorganisms, including viridans streptococci, decreased in the benzalkonium chloride and the nonoxynol 9 plus benzalkonium chloride groups. Detection of Lactobacillus species decreased in the benzalkonium chloride group. All microflora levels recovered after several days without microbicide use. Although nonoxynol 9 is currently the only microbicide approved for use as a spermicide in the United States, its repeated use may be detrimental to the epithelial tissues of the female reproductive tract. Benzalkonium chloride, currently approved for use in other countries, not only may damage epithelial tissues but also appears to reduce the population of potentially protective Lactobacillus species in the vagina.