PhD Candidate University of Texas at Austin Austin, Texas
Nexplanon® is a subdermal implant made of ethylene vinyl acetate (EVA) that prevents pregnancy for up to three years by providing prolonged and controlled release of etonogestrel, a contraceptive hormone. Despite its widespread use, the material and structural properties of the implant—and how these influence drug release—remain insufficiently characterized. One major challenge is that studying drug release over the full three-year duration is both time-consuming and labor-intensive. In this presentation, the key material and structural attributes that control long-acting drug release from Nexplanon® will be discussed. The underlying release mechanisms will be explained from both a physical standpoint and a mathematical modeling perspective. We will also revisit the classic Higuchi model, modifying it to account for the cylindrical geometry of the implant and the presence of an unstirred water layer surrounding the implant surface during drug release (boundary layer effect). The mechanistic insights gained from this work were used to develop a mathematical modeling framework that successfully predicts Nexplanon® drug release for up to 3.5 years.
Learning Objectives:
understand the key material and structural attributes that controlled the long-acting drug release of Nexplanon® implant.
use mechanistic models to determine when dissolution or diffusion becomes the rate-limiting step in Nexplanon® drug release.
understand the drug-release mechanisms of Nexplanon® and utilize mathematical models to predict release profiles for up to five years.
