Levonorgestrel
"I am very happy with my Mirena, BESIDES the horrible acne.  I was on birth control pills to help take care of it.  Every time my body thinks I am going to get my period, I break out pretty bad. Insertion of the Mirena was very, very painful. I would highly suggest asking for something for the pain if you have not had kids, get bad cramps anyway and are planning on getting this placed.  I was so sore for the first few weeks.  Every once in while I will get random cramps on the one side where I always got really, really bad cramps.  But they are so minimal in comparison.  Was good choice!"