Levonorgestrel-piroxicam Versus Ulipristal Acetate for Emergency Contraception

The goal of this clinical trial is to compare the failure rate of the levonorgestrel (LNG)-piroxicam combination regimen versus ulipristal acetate (UPA) as emergency contraception (EC). The main questions it aims to answer are:

1. whether the LNG-piroxicam combination regimen has a lower failure rate than UPA for EC; 2. whether the LNG-piroxicam combination regimen has a higher percentage of pregnancies prevented than UPA for EC 3. whether there is any difference in the change in the subsequent menstrual cycle and adverse effect profile between the two regimens

Participants will:

1. Take a single dose of either (i) LNG 1.5 mg plus piroxicam 40 mg and a placebo tablet resembling UPA, or (ii) UPA 30 mg plus placebo tablets resembling LNG and piroxicam. 2. Have a blood test for serum LH, oestradiol an progesterone. 3. Keep a diary of their vaginal bleeding episodes, adverse effects symptoms, any further acts of intercourse and the type of contraception used. 4. Have a follow-up either in person by phone about 1-2 weeks after the next expected menstruation. 5. If normal menstrual bleeding has not occurred by that time, a pregnancy test will be carried out.