Rectal Applications of Nonoxynol-9 Cause Tissue Disruption in a Monkey Model

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Abstract
Efforts to develop topical microbicide products have all but ignored evaluation for rectal use. The goal of this study was to assess the effects of multiple rectal applications of Conceptrol (containing 4% nonoxynol-9) on flora and mucosal tissues in the pig-tailed macaque model. Monkeys (8 per group) received daily rectal applications of Conceptrol, placebo gel, or no product, for 3 days. At each visit, a preapplication rectal lavage specimen and swab specimen for microbiology and pH determination were collected. Conceptrol or placebo gel (2.5 ml) was then administered intrarectally. Fifteen minutes after application, samples were again collected. Gross observation of rectal lavage indicated sheets of epithelium 15 minutes after application of the nonoxynol-9 product. Histopathology of these samples revealed epithelial sheets with stroma attached. The presence of H2O2-producing lactobacilli remained relatively constant, whereas that of H2O2-producing viridans streptococci diminished in all nonoxynol-9-exposed animals in which these organisms were detected at baseline. Repeated applications of nonoxynol-9 disrupts the rectal mucosa of the pig-tailed macaque. The disruption of these tissues could have serious implications for an increase in likelihood of acquisition of sexually transmitted infection/HIV in humans.