Prospective long-term study of etonogestrel contraceptive implant insertion at an alternative scapular site - Project Summary (Abstract): The etonogestrel (ENG) contraceptive implant remains the most effective hormonal contraceptive method currently available. However, uptake of the ENG implant is hindered by persistent, rare insertion-related side effects including neurovascular injury and implant migration. These rare yet morbid side effects are directly related to the insertion of the implant in the non-dominant arm. An alternative insertion site in the lower scapular region not only alleviates the risk of these insertion-related side effects, but also has unique benefits for specific patient populations. The subdermal scapular insertion site is distant from any danger zones containing neurovascular structures, has a bony structure preventing deep implant insertion, and is a less-accessible area of the body. For patients with developmental delays or psychotic conditions, a less-accessible area of implant insertion is ideal to maintain reliable contraception while preventing self-removal attempts. We developed reliable insertion and removal techniques for the ENG implant at this alternative scapular site as part of a pilot study, while also establishing similar pharmacokinetic profiles for the first year of implant use. However, to support the potential clinical use of the scapular-site inserted ENG implant for its full three-year approved duration of use, we need longer-term pharmacokinetic and pharmacodynamic data from a larger cohort of participants. We aim to conduct a prospective two-year study of the ENG implant when inserted at this alternative subdermal scapular insertion site among 62 healthy, reproductive-age females. We will collect serial pharmacokinetic data from all participants measured at every 6-months over the course of two years of use (4 total measurements). We will utilize these pharmacokinetic data to test for bioequivalence between insertion of the ENG implant at this alternative subdermal scapular site and published pharmacokinetics with standard arm insertion. All participants will also complete questionnaires to assess their side effect profiles and bleeding patterns at each 6-month follow-up time point. We will compare side effect patterns and bleeding profiles from all 62 participants with scapular-inserted ENG implants to published rates from standard arm-inserted ENG implant users. Finally, we will offer all participants enrollment into our existing biobank for future pharmacogenomic and precision medicine investigations. This study will provide the first comprehensive pharmacokinetic and pharmacodynamic data for insertion of the ENG implant at this alternative subdermal scapular site out to two years of use. We will utilize these data to support this alternative insertion site as a clinically viable option for patients, especially among patient populations with contraindications or previous complications with standard arm insertion, and as preliminary data for funding applications to extend this trial out to 3-5 years of implant use. Clinicians will be able to directly incorporate the findings from this study into counseling regarding the contraceptive efficacy and side effect expectations for patients considering an ENG implant inserted at the subdermal scapular site.
