Cupric Ion Release from Various IUD Geometries

Intrauterine Devices (IUDs) are gaining popularity as a form of long-acting reversible contraceptives (LARC); once inserted, copper IUDs can be effective for up to ten years and require no action from the user. The contraceptive effect of copper IUDs is believed to be at least partially due to the spermicidal effect of cupric ions in the uterine cavity, as well as the inflammatory immune response induced by the foreign object. The release of cupric ions depends on the surface area of copper, IUD geometry and physiological factors. Negative side effects from IUDS, such as pain and bleeding, are also related to IUD shape and uterine anatomy. There has been increased interest in developing new IUD designs that minimize these unwanted side effects while maintaining contraceptive effectiveness. In order to implement new IUD designs, animal testing and clinical trials are stages in which prototypes are determined to be effective. To minimize risk, a computer-simulated model can predict how an IUD will behave in vivo. However, a computer-simulated model of cupric ion release from IUDs does not presently exist. Therefore, this study accomplished the goal of developing a physiologically accurate digital model of cupric IUD erosion patterns in the uterus. By using COMSOL, a physiologically accurate model of an IUD in vivo was created. Then, the diffusion behavior of copper in two different domains – the uterine fluid and the blood – was simulated. Because the copper IUD will release copper ions as it erodes, the concentrations of copper in the two domains were dependent on the mass flux of copper out of the IUD. The concentration of copper in these domains was also affected by copper removal, which occurs through convective flux in the blood and cervical flux. The concentration of copper ions in the uterine fluid and blood were tracked over a period of 1 year. As a result, this model allowed investigators to determine the parameters at which a digitally modeled copper IUD is most physiologically accurate. The T-shaped copper IUD can be accurately modeled in COMSOL by using accurate parameters and incorporating a periodic function for increases in copper flux throughout the menstrual cycle