In two recent Phase III clinical trials, use of a 25 mg dapivirine vaginal ring significantly reduced HIV acquisition rates. Post hoc analysis from one of the trials indicated higher rates of protection among women over the age of 21 years when compared to younger women, most likely due to reduced adherence in the latter group. There is currently no information available on how release of dapivirine from the ring is affected by either its intermittent removal from the vagina or women's cleaning of the ring before re-insertion. Here, in vitro drug stability and product performance characteristics of the dapivirine ring were assessed under simulated conditions of real-world use. The impact of systematic deviations from the 28-day continuous use protocol upon in vitro release performance, was investigated. Also, the effect of ring exposure to a range of common household chemicals - including bath salts, bleach, detergent and personal lubricants - was examined through measurement of dapivirine content and stability. Dapivirine in vitro release under intermittent schedules was similar to that obtained under the normal continuous schedule ignoring the periods of interruption. Ring exposure to various household chemicals had no discernible impact on dapivirine assay value, degradation or stability.
Keywords: Antiretroviral; HIV microbicide; Intermittent use protocol; Silicone elastomer vaginal ring.
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