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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