Case study 1
HN is 17 years old and has made an appointment with her nurse practitioner to discuss emergency contraception. At the consultation, HN is clearly distressed and explains that she had unprotected sexual intercourse with her boyfriend the night before and that she is not on the pill. After finding out that HN does not want an IUD which is 99% effective for emergency contraception, the nurse practitioner prescribes a high dose progestin-only preparation and provides HN with instructions on dosage and potential adverse effects. She also asks HN to consider the possibility of taking the pill from now on. HN agrees that this is a good idea, so her nurse practitioner adds an oestrogen-progestogen combination oral contraceptive to the prescription. The emergency contraception is successful.
HN revisits her nurse practitioner after several months of starting to take the pill. She has suffered no ill effects associated with taking the pill but is in a panic because she has missed a dose a day earlier and wants to know what she should do.
1) Explain how postcoital progestin-only contraceptives work?. (seventy-one hundred words)