Levonorgestrel
"I'm 18 with no children and had Mirena inserted about 3 weeks ago. The procedure was pretty painful for me but it went quick and no tears so I got through that. I got right up and continued on the cramping, started instantly and was pretty intense, so I took something for it and called it a day early. I got the Mirena inserted for regulation of my period, and because I'm leaving for college and am aware that my schedule will get hectic so I wanted new source of birth control (I've been on the pill since 12/13 yrs old) . I haven't had any other symptoms besides cramping. I rarely cramped before so this cramping to me is intense. They usually aren't continuous cramps, in and out something like a spasm."