Hormonal Emergency Contraception

Melissa Sanders Wanner, Pharm.D., Rachel L. Couchenour, Pharm.D.


Pharmacotherapy. 2002;22(1) 

In This Article

Abstract and Introduction

In the 1960s, high-dose estrogen was identified as a highly effective emergency contraceptive but was associated with a high frequency of nausea and vomiting. The combination of low-dose estrogen and a progestin (the Yuzpe regimen) is highly effective and much better tolerated. Recently, a progestin-only regimen containing levonorgestrel was found to be more effective than the Yuzpe regimen and caused significantly less nausea and vomiting. Danazol, an antigonadotropin, is well tolerated but has questionable efficacy. Mifepristone has several pharmacologic actions that make it highly effective with an adverse-effect profile similar to that of the Yuzpe regimen. Progress has been made in the last 3 years toward increasing the number of emergency contraceptives that are accessible to women in the United States, and several highly effective options are available. The most effective and well-tolerated regimen available is levonorgestrel. However, the barriers to access and low patient and provider awareness limit the impact of emergency contraception on the rate of unintended pregnancies.

An emergency contraceptive is a drug or device intended to prevent pregnancy after unprotected intercourse.[1] Hormonal emergency contraception involves taking high-dose estrogen, estrogen plus a progestin, progestin alone, danazol, or mifepristone as soon as possible after unprotected intercourse (Table 1). Commonly used terms such as postcoital contraception and morning-after pills should be avoided because they imply that these methods must be used immediately after or at the latest "the morning after" the intercourse.[4] Available hormonal emergency contraception may be used effectively up to 72 hours after unprotected intercourse.

In the United States, one-half of the 6 million pregnancies/year are unintended, and approximately one-half of those unintended pregnancies end in abortion. The widespread availability of effective, well-tolerated forms of hormonal emergency contraception could prevent an estimated 2 million unintended pregnancies and 1 million abortions each year.[5]

High-dose estrogen was one of the first hormonal products studied as emergency contraception in the 1960s. It was found to be effective but was associated with a high frequency of adverse effects such as nausea and vomiting.[6] A combination estrogen and progestin regimen was described in the late 1970s and is commonly referred to as the Yuzpe regimen.[7] This regimen has gained popularity because of its high efficacy and considerably improved tolerability over high-dose estrogen. Danazol, an antigonadotropin, was investigated for emergency contraception in an effort to identify an equally effective agent with a more favorable adverse-effect profile. Its efficacy has been questioned, and the search for alternative methods continued.[8,9] A progestin-only regimen containing levonorgestrel is one of the most recent options for emergency contraception and is also very effective and well tolerated.[10] Although unavailable to women in the U.S. for emergency contraception, mifepristone is another very effective and well-tolerated option.[8]


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