Background: The oral contraceptive pill (OC) and the contraceptive ring are often prescribed in an extended manner to achieve amenorrhea, reduce menstrual-related symptoms and improve method adherence. Concerns regarding thromboembolic risk may lead providers to avoid offering the contraceptive patch as an extended contraceptive regimen beyond the label indicated use of 3 weeks.
However, data are unclear about a possible increased risk of venothromboembolism (VTE) among users of the patch, especially when compared to users of oral contraception. Epidemiologic data suggest minimal increased VTE risk, and previous pharmacokinetic data conflict regarding accumulation of EE2 levels specifically over time.
Objectives: We sought to assess the change in serum ethinyl estradiol (EE2) and norelgestromin (NGMN) levels over 12 weeks of continuous contraceptive patch use.
Study Design: We asked participants (n=30) to apply consecutive patches to be worn continuously (without a patch-free interval) for 12 weeks. We collected serum blood draws at the end of each patch week and two times during weeks 4, 8, and 12 (with the additional blood draw occurring mid-week). Liquid chromatography-tandem triple quadrupole mass spectrometry coupled with mass spectrometry analysis (LC-MS/MS) was utilized to assess EE2 and NGMN levels.
Results: 27 women completed the study; 26 were compliant with patch use. The change in EE2 levels ranged from 0 to 160 pg/ml over the 12 week period. The slope of the fitted line demonstrates an accumulation over the 12 week time and is significant. The change in NGMN levels ranged from 0 to 2.5 ng/ml over the 12 week period. The slope of the fitted line for NGMN is equal to zero. The most common expected adverse effect reported was abdominal pain and cramping. There were no serious adverse events reported.
Conclusion: The data suggest an accumulation of EE2 over the 12 week study period. While the results are variable for EE2 levels, the absolute values remain low and within the expected range as listed in the product labeling. There remains limited data regarding the risk associated with a certain EE2 level.