Q: Are there any post-intercourse pills to prevent a pregnancy?

A:You are presumably referring to what are commonly known as the morning after pills. These pills are taken within 72 hours of unprotected intercourse and they prevent the implantation of the zygote in the uterus. An initial high-dose combined pill is given immediately after unprotected sex while another dose is given 12 hours later. The failure rate is about 2-3%. Commonly, ethinylestradiol 5 mg is given for 5 days starting not later than 36 hours after intercourse. Though this is effective, it may cause nausea and vomiting. Any medication should be taken under a gynaecologist's supervision.