Yuzpe regimen
The Yuzpe Regimen is a method of emergency contraception using a combination of estrogen and progestogen hormones and started within 72 hours of sexual intercourse. It has subsequently been superseded by a progestogen-only hormonal regimen.

# History
The method was first developed by a Canadian Professor A. Albert Yuzpe who published the first studies demonstrating the method's safety and efficacy in 1974.

# Description
This regimen allows a woman who has had unprotected sex to avoid pregnancy by taking 12 hours apart two sufficient doses of estrogen and progestogen hormones. The sooner this is started, the more effective it is and the effectiveness more than 72 hours after sexual intercourse is greatly  reduced. The licensing for emergency Intrauterine device (IUD) insertion allows for up to 5 days and it is highly effective for up to five days after the time of ovulation, which may extend more than five days after the relevant risky intercourse.
These hormones are administered as a number of combined oral contraceptive pills (COCPs). Each dose can vary from 2 to 5 pills depending on the brand of medication being used. Patients concurrently taking certain regular medications (e.g. rifamycin and many anticonvulsant drugs) that enhance the liver's break down of other drugs, must use an even higher hormone dose and may be better advised to use as an alternative the insertion of an IUD.
The standard regime is two tablets each with 50 g ethinyl estradiol and 250 g levonorgestrel, to be repeated 12 hours later.
The method is not guaranteed to prevent pregnancy and whilst the hormones may make the subsequent period come a few days early or late, a pregnancy test should be carried out if the period is more than 3 days late. The Yuzpe Regimen does not protect against sexually transmitted diseases.
Subsequently, the World Health Organization (WHO) undertook an investigation into the use of progestogen-only tablets as an Emergency Hormonal Contraceptive (i.e. without any estrogen component). This showed greater efficacy with reduced side effects and has therefore superseded the Yuzpe method.  A single dose of 100 mg mifepristone is also more effective than the Yuzpe regime.

# Side effects
Some temporary, but usually minor, reactions include:
- Nausea and/or vomiting
- Breast tenderness
- Irregular Bleeding
- Headache or Dizziness
Should vomiting occur within 3 hours of taking a dose, then insufficient hormones may have been absorbed to provide the full contraceptive cover and an additional dose should be taken. Measures that may help to prevent nausea or vomiting include:
- Take the pills with food.
- Take Dramamine or Bonine an hour before taking the pills, if you are especially sensitive to or bothered by nausea -- however, this step is not necessary.
- Schedule your doses so that you take the second dose before bed.

# Formulations
Many common combined oral contraceptive pills could be used for the Yuzpe regimen, although their manufacturers did not label the pills for this use. Such off-label use of approved medications is legal and commonplace in American medicine. Further, in February 1997, the FDA declared emergency contraceptive use of certain birth control pills, following the Yuzpe regimen, as safe and effective.
Yuzpe regimen dedicated products (Preven in US and Schering-PC4 in UK) were discontinued following the introduction of progestogen-only ECPs (Plan B in US and Levonelle in UK).