Development and evaluation of a vaginal ring device for sustained delivery of HIV microbicides to non-human primates

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.