Levonorgestrel
"I took this pill approximately 8 hours after my husband and I had intercourse. After missing my period I thought no way! I can't be pregnant maybe my periods are just thrown off.. the other day I purchased a pregnancy test just to be sure and it was a big fat POSITIVE!!! ladies please be careful taking this pill. I've taken "plan b" in the past and had great luck but this one definitely doesn't compare.. USE WITH CAUTION."