In previous study, certain HIV medications were found to lower the effectiveness of some hormonal contraceptives, including the NNRTI efavirenz (Sustiva). This presented concerns about the experimental NNRTI dapivirine that was already being used as a vaginal ring for PrEP in clinical study. A presentation at the 2017 Conference on Retroviruses and Opportunistic Infections showed that this is not the case with the dapivirine ring.
The Phase 3 ASPIRE study reported in 2016 that the dapivirine ring reduced HIV infections 27% in 2,629 women, half of whom used the dapivirine ring and half of whom used a placebo. However, no data were available at that point about whether the drug also lowered the effectiveness of injected, implant or oral contraceptives and thereby possibly increasing the number of pregnancies.
In ASPIRE, all women had to use a reliable hormonal form of contraception (injected DMPA or NET-EN, implant or oral pill) in addition to the ring, and regular pregnancy tests were done monthly. If a participant become pregnant, the ring was withdrawn for the duration of pregnancy and breastfeeding.
This year’s follow-up analysis showed the incidence of pregnancy among the women. There were 117 pregnancies among 114 women (some women had more than one pregnancy during the study). The rate of pregnancy was 0.49 for injected DMPA, 0.58 for injected NET-EN, 0.45 for implants and 30.21 for pills, none of which differed significantly whether a woman received the active dapvirine or placebo riing.
Although the pregnancy rate for oral pills was high and may point to poor adherence, none of these rates differed between the two groups. This led the researchers to conclude that dapivirine given through a vaginal ring did not affect the effectiveness of hormonal contraceptives.
J Balkus, et al. Dapivirine Ring Use Does Not Diminish the Effectiveness of Hormonal Contraception. 2017 CROI, Seattle. Abstract 88.