Warfarin

What is Warfarin

Warfarin is an oral coumarin anticoagulant. In 1939, it was discovered that spoiled sweet clover possessed anticoagulant properties due to the presence of a compound identified as bishydroxycoumarin.

In 1948, a potent congener was introduced as an effective rodenticide; this compound was named warfarin. Warfarin is a racemic mixture of two active isomers; the S-isomer is 3 to 5 times as potent as the R-isomer. Clinically, warfarin is used to prevent and treat thromboembolic disease in patients with various clinical conditions.

By adopting the International Normalized Ratio (INR) method of monitoring warfarin therapy and decreasing the intensity of anticoagulation for most indications, the major hemorrhagic risks of warfarin therapy have decreased substantially. 

Indications

  1. angina
  2. antiphospholipid antibody syndrome
  3. arterial thromboembolism prophylaxis
  4. atrial fibrillation
  5. cardiomyopathy
  6. coronary artery thrombosis prophylaxis
  7. deep venous thrombosis (DVT)
  8. deep venous thrombosis (DVT) prophylaxis
  9. heart failure
  10. myocardial infarction prophylaxis
  11. postmyocardial infarction
  12. prosthetic heart valves
  13. pulmonary embolism
  14. pulmonary embolism prophylaxis
  15. stroke prophylaxis
  16. thrombosis prophylaxis
  17. unstable angina
  18. warfarin anticoagulation

Side Effects

  1. alopecia
  2. anaphylactoid reactions
  3. anemia
  4. angina
  5. asthenia
  6. bleeding
  7. bone fractures
  8. calciphylaxis
  9. chest pain (unspecified)
  10. chills
  11. cholesterol microembolization
  12. coma
  13. diarrhea
  14. dizziness
  15. dysgeusia
  16. ecchymosis
  17. edema
  18. elevated hepatic enzymes
  19. epistaxis
  20. exfoliative dermatitis
  21. fatigue
  22. fever
  23. flatulence
  24. GI bleeding
  25. headache
  26. hematuria
  27. hepatitis
  28. hypotension
  29. intracranial bleeding
  30. jaundice
  31. lethargy
  32. maculopapular rash
  33. malaise
  34. nausea
  35. ocular hemorrhage
  36. pallor
  37. paresthesias
  38. petechiae
  39. priapism
  40. pruritus
  41. purple-toe syndrome
  42. retroperitoneal bleeding
  43. skin necrosis
  44. spontaneous fetal abortion
  45. syncope
  46. teratogenesis
  47. tissue necrosis
  48. urticaria
  49. vaginal bleeding
  50. vomiting

Monitoring Parameters

  • INR
  • prothrombin time (PT)
  • stool guaiac

Contraindications

  • alcoholism
  • anemia
  • aneurysm
  • anorexia nervosa
  • aortic dissection
  • Asian patients
  • atrial fibrillation
  • bleeding
  • breast-feeding
  • bulimia nervosa
  • cardiac disease
  • cerebrovascular disease
  • children
  • cholestasis
  • contraception requirements
  • coumarin anticoagulants hypersensitivity
  • dementia
  • dental work
  • diabetes mellitus
  • diarrhea
  • eclampsia
  • endocarditis
  • epidural anesthesia
  • fever
  • geriatric
  • GI bleeding
  • head trauma
  • heart failure
  • hematological disease
  • hemophilia
  • heparin-induced thrombocytopenia (HIT)
  • hepatic disease
  • hepatitis
  • hyperlipidemia
  • hypertension
  • hyperthyroidism
  • hypothyroidism
  • immune thrombocytopenic purpura (ITP)
  • infants
  • infection
  • intracranial bleeding
  • intramuscular injections
  • jaundice
  • labor
  • leukemia
  • lumbar puncture
  • neonates
  • neoplastic disease
  • obstetric delivery
  • peptic ulcer disease
  • pericardial effusion
  • pericarditis
  • peripheral edema
  • polycythemia vera
  • preeclampsia
  • pregnancy
  • pregnancy testing
  • protein C deficiency
  • protein S deficiency
  • psychosis
  • renal disease
  • renal failure
  • renal impairment
  • reproductive risk
  • retinal bleeding
  • spinal anesthesia
  • stroke
  • surgery
  • tobacco smoking
  • vasculitis
  • vitamin C deficiency
  • vitamin K deficiency

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