Levonorgestrel
"Over the past weekend my boyfriend and I had a 'uh oh' accident. About 5 hours later I went to walgreens and got plan B (which I found out is no longer over the counter). It works great!  It's a little expensive but it beats having a baby in my belly! I'm so glad this product exist. If your afraid to take it, don't be! As long as you take it within 72 hours you'll be fine. But the sooner you take it the better."