Possible side effects of coagulants include:

• Unusual bleeding (gastrointestinal, urinary tract, etc.)
  
  
• Osteoporosis
  
  
• Cloudy, red or dark urine
  
  
• Allergic reaction
  
  
• Fever or chills
  
  
• Skin necrosis, or death, usually located on the extremities, including the breasts, trunk and penis in males
  
  
• Blue or purple toes
  
  
• Edema (swelling) of eyelids, face or lips
  
  
• Congenital defects of the fetus when administered during pregnancy

Coumadin paradox is a rare condition which may occur early (within three days) of adminstration of the anitcoagulant warfarin (coumadin). The condition is associated with increased tendency to form blood clots. To avoid this condition, heparin can be adminstered together with warfarin because its action is immediate. When the anticoagulant effect of warfarin is evident, heparin can be discontinued.

Up to 5 percent of individuals taking heparin may develop heparin-induced thrombocytopenia (HIT), or delayed-onset HIT – reactions that can increase the risk of the formation of new clots. Research is ongoing in the development of “antidotes” that can be given to counter the effects of this complication. Some of the newer anticoagulants being developed may reduce the risk of this condition.