The morning after pill can be taken the morning after sexual activity in order to avoid pregnancy. Plan B or levonorgestrel can be taken up to 3 days after “unprotected” sexual activity.  According to some sources, plan B doesn’t work on women over 165 lbs. It requires no prescription.  Ella, another type of medication available, requires a prescription and can be taken up to 5 days after “unprotected” sexual activity. These are synthetic female hormones.