Post-use ring weight, residual drug content and drug depletion zone thickness as objective measures of vaginal ring adherence

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Abstract

Background: A challenge in the development of microbicide-releasing vaginal rings is the accurate and reliable measurement of adherence during clinical testing. To move away from self-reported measures of adherence, there is considerable interest in the development and testing of more objective, quantitative measures. Here, we assessed post-use ring weight, residual drug content and drug depletion zone thickness as potential measures of adherence to a highly-loaded progesterone-releasing ring.

Methods: Matrix-type silicone elastomer vaginal rings containing progesterone (n=89) were used by breastfeeding women across three sites in Africa to extend the contraceptive effectiveness of lactational amenorrhea. Used rings were assessed for ring weight, residual progesterone content (via solvent extraction and HPLC- UV analysis), and drug depletion zone thickness (using digital microscopy) as potential measures of user adherence.

Results: Unused control rings (n=6) had a mean progesterone content of 2058 ± 21 mg (99.2 ± 1.0 %; relative to 2074 mg nominal loading) and mean ring weight of 9.37 ± 0.02 g. Mean residual progesterone content and post-use ring weight for clinical rings were 1212 ± 220 mg and 8.60 ± 0.22 g, respectively. Wide variations in residual progesterone content (range 45.5-99.2% of controls) and ring weight (range 88.0-99.9%) of used rings were attributed to differences in extent of ring use. Linear correlations were observed between residual progesterone content and post-use ring weight (r2=0.7331), and thickness of the drug depletion zone with post-use ring weight (r2=0.9757) and residual drug content (r2=0.9743).

Conclusions: For vaginal rings with a high drug load like the matrix- type progesterone ring, where a relatively large fraction of the initial drug loading is released during use; post-use ring weight, residual drug content and depletion zone thickness may offer accurate methods for monitoring user adherence. Ring weight measurement offers a particularly simple and inexpensive method.
Original languageEnglish
PagesP25.16
Publication statusPublished - 25 Oct 2018
EventHIV Research for Prevention 2018 - Madrid Marriott Auditorium Hotel, Madrid, Spain
Duration: 21 Oct 201825 Oct 2018
http://www.hivr4p.org

Conference

ConferenceHIV Research for Prevention 2018
Abbreviated titleHIVR4P 2018
CountrySpain
CityMadrid
Period21/10/201825/10/2018
Internet address

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