Document Detail

The "Warfarin Window" in Pregnancy: The Importance of Half-life.
MedLine Citation:
PMID:  21176310     Owner:  NLM     Status:  In-Data-Review    
Anticoagulation therapy during pregnancy in women with prosthetic cardiac valves is a therapeutic challenge. The use of vitamin K antagonists such as warfarin during pregnancy carries the potential for serious risks to the fetus, especially if these drugs are administered during the first trimester or at term. Between 6 and 12 weeks' gestation, fetal synthesis of proteins crucial for bone and cartilage formation may be impaired by warfarin, resulting in the well-defined "warfarin embryopathy." One of the most commonly suggested regimens involves the substitution of heparin for warfarin between 6 and 12 weeks' gestation to minimize the risk of warfarin embryopathy. Warfarin has a long half-life; following a single dose, the terminal elimination half-life is about one week, with a mean effective half-life of 40 hours. To date, all existing guidelines have ignored this long elimination half-life. If a policy of substituting heparin for warfarin between 6 and 12 weeks' gestation is followed, we suggest that substitution should begin at a much earlier gestational age. Substitution starting at 6 weeks' gestation may be too late to avoid embryopathy.
Asnat Walfisch; Gideon Koren
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstétrique et gynécologie du Canada : JOGC     Volume:  32     ISSN:  1701-2163     ISO Abbreviation:  J Obstet Gynaecol Can     Publication Date:  2010 Oct 
Date Detail:
Created Date:  2010-12-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101126664     Medline TA:  J Obstet Gynaecol Can     Country:  Canada    
Other Details:
Languages:  eng     Pagination:  988-9     Citation Subset:  IM    
Motherisk Program, Hospital for Sick Children, Toronto ON.
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