Thursday, June 4, 2015

Warfarin use in Hyperthyroid and Hypothyroid


Hyperthyroidism  
  • Increased sensitivity to warfarin
  • The mechanism may be that thyroxine increases the affinity of warfarin for receptor sites in the liver, leading to decreased production of clotting factors
  • Another mechanism may be increased catabolism of vitamin K dependent clotting factors 
Hypothyroidism
  • Decreased response to warfarin
  • The mechanism may be decreased catabolism of vitamin K dependent clotting factors
Carbimazole & Propylthiouracil
  • Decrease the anticoagulant effect of warfarin by either by increasing its metabolism or indirectly by interfering with absorption
Levothyroxine
  • Increase anticoagulant effect 
  • Increasing thyroid hormone levels can increase sensitivity to warfarin which may increase the risk of bleeding
REFERENCE :  

  1. http://www.medscape.com/viewarticle/410539_3   
  2. http://www.aafp.org/afp/2000/1115/p2318.html
  3. http://www.inronline.net/index.php/information/179-2/drug-interactions/
  4. http://www.rxlist.com/drug-interactions/propylthiouracil-oral-and-warfarin-oral-interaction.htm
  5. http://www.rxlist.com/drug-interactions/levothyroxine-oral-and-warfarin-oral-interaction.htm  
  6. http://www.bpac.org.nz/BPJ/2007/April/warfarin.aspx
  7. LEXICOMP 

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