Background: There is considerable interest in developing coitally independent, sustained release formulations for long-term administration of HIV microbicides. Vaginal ring devices are at the forefront of this formulation strategy.
Methods: Non-medicated silicone elastomer vaginal rings were prepared having a range of appropriate dimensions for testing vaginal fit in pig-tailed and Chinese rhesus macaques. Cervicovaginal proinflammatory markers were evaluated. Compression testing was performed to compare the relative flexibility of various macaque and commercial human rings.
Results: All rings remained in place during the study period and no tissue irritation or significant induction of cervicovaginal proinflammatory markers or signs of physical discomfort were observed during the 8-week study period.
Conclusions: Qualitative evaluation suggests that the 25 x 5-mm ring provided optimal fit in both macaque species. Based on the results presented here, low-consistency silicone elastomers do not cause irritation in macaques and are proposed as suitable materials for the manufacture of microbicide-loaded vaginal rings.