Effects of switching from oral to transdermal or transvaginal contraception on markers of thrombosis

Background The study was conducted to determine the impact of switching from oral to transdermal patch or vaginal ring contraception on biomarkers of thrombosis. Study Design Current healthy oral contraceptive (OC) users were randomized to switch to either a contraceptive ring (CR) or patch (CP) and underwent phlebotomy to measure surrogate biomarkers of thrombosis [sex hormone-binding globulin (SHBG), free protein S and activated protein C resistance (APC-r)] before switching, and during the fourth cycle of use of the new method. Results Of 142 reproductive age women enrolled, 120 sample pairs were available for analysis. SHBG increased significantly from baseline in CP users [mean change (95% CI), +29.9 nM (9.6–50)] but not in CR users [−1.6 (−16.6 to 13.5)]. Protein S decreased significantly from baseline in CP users [mean change −7.1% (−12.1 to −2.1)], but increased significantly in CR users [+5.3% (1.1–9.6)]. The APC-r ratio did not undergo a significant change from baseline in either group [CP +0.06 (−0.06 to 0.18), CR +0.02 (−0.10 to 0.14)]. Compared to CR users, subjects using the CP had significantly higher SHBG [187.5 (167.0–208), 146 (132.6–159.4), p=.012], significantly lower protein S [81.8 (76.8–86.8), 93.6 (89.1–98.1), p=.001] and similar APC-r ratios [2.99 (2.85–3.14), 3.09 (2.96, 3.22), p=.3] at the Cycle 4 visit. Conclusion OC users who switch to the ring exhibit beneficial changes in biomarkers of thrombosis, while those switching to the patch display a shift favoring clot formation.