| Mechanisms of action of hormonal emergency contraceptives. | |
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MedLine Citation:
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PMID: 20099990 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Hormonal emergency contraceptives have been used to prevent unwanted pregnancy for more than 3 decades. The mechanisms of action of the regimen containing a combination of estrogen and progestin, known as the Yuzpe regimen, and those of the levonorgestrel regimen continue to be controversial, especially over the possibility that these regimens might act by interfering with implantation of the fertilized ovum. We performed a search of the PubMed (1949-July 2009) and EMBASE (1980-July 2009) databases to identify literature on the mechanisms of action of these contraceptive regimens, and data were extracted from pertinent English-language studies. We classified studies according to the approach taken by the investigators to study the actions of emergency contraceptives on pregnancy: an indirect method that uses statistical models to determine whether emergency contraceptives would be as effective as reported if they act only by disrupting ovulation; direct observation of the effects of emergency contraceptives on surrogate outcomes, including ovulation, sperm activity, hormonal levels, and endometrial receptivity to implantation; and analysis of directly observed pregnancy outcomes against statistical data. Acceptability of emergency contraceptives by women and clinicians may depend on personal opinions about when life or pregnancy begins. The evidence strongly supports disruption of ovulation as a mechanism of action. The data suggest that emergency contraceptives are unlikely to act by interfering with implantation, although the possibility has not been completely excluded. The data also suggest that emergency contraceptives are ineffective after ovulation. Women and clinicians who consider implantation or later events to be the beginning of pregnancy should be aware that emergency contraceptives are likely nonabortive by this definition of pregnancy. |
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Authors:
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Vivian W Y Leung; Marc Levine; Judith A Soon |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Review |
Journal Detail:
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Title: Pharmacotherapy Volume: 30 ISSN: 1875-9114 ISO Abbreviation: Pharmacotherapy Publication Date: 2010 Feb |
Date Detail:
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Created Date: 2010-01-26 Completed Date: 2010-04-22 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8111305 Medline TA: Pharmacotherapy Country: United States |
Other Details:
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Languages: eng Pagination: 158-68 Citation Subset: IM |
Affiliation:
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Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Contraceptive Agents, Female / pharmacology* Contraceptives, Oral, Hormonal / pharmacology* Contraceptives, Postcoital / pharmacology* Ethinyl Estradiol-Norgestrel Combination / pharmacology Female Humans Levonorgestrel / pharmacology Models, Biological Models, Statistical Ovulation / drug effects* Pregnancy Pregnancy, Unwanted / drug effects* Reproduction / drug effects*, physiology Treatment Outcome |
| Grant Support | |
ID/Acronym/Agency:
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//Canadian Institutes of Health Research |
| Chemical | |
Reg. No./Substance:
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0/Contraceptive Agents, Female; 0/Contraceptives, Oral, Hormonal; 0/Contraceptives, Postcoital; 797-63-7/Levonorgestrel; 8056-51-7/Ethinyl Estradiol-Norgestrel Combination |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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