Warfarin

Question 1

Therapeutic Classification

Answer 1

Anticoagulant

Question 2

Pharmacologic Classification

Answer 2

Vitamin K antagonist

Question 3

Mechanism of Action

Answer 3

• Inhibits two enzymes involved in formation of activated vitamin K
• Inhibits synthesis of new clotting factors
• Antidote = vitamin K

Question 4

Indications

Answer 4

• Prophylaxis arterial thromboembolism
• DVT
• Pulmonary embolism
• Long-term indwelling catheters

Question 5

Precautions

Answer 5

• Dental procedures

- CHF (can exacerbate)

Question 6

Contraindications

Answer 6

• Recent trauma
• Active internal bleeding
• Serious bleeding disorders
• Intracranial hemorrhage
• Severe HTN
• Bacterial endocarditis
• Severe hepatic/renal impairment
• Pregnancy
• IM injections of other medications should be avoided because they may cause bruising, bleeding, or hematomas.
• Patients with heart failure may exhibit excessive anticoagulation with warfarin.

Question 7

Adverse Effects

Answer 7

• *Abnormal bleeding
• Microembolism
• Osteoporosis

Question 8

Nursing Considerations

Answer 8

• Complete health history
• Monitor PT/INR (2 -2.5)
• Monitor urine, stool, liver function, and blood
• Monitor risk groups for nonadherence

Question 9

Patient & Family Teaching

Answer 9

• Anticoagulants including warfarin carry a black box warning related to the increased risk of bleeding and hemorrhage. This risk is especially of concern in early administration and in high doses.
• Use extra precautions to avoid pregnancy.
• Report bleeding symptoms
• Stop drug and immediately report signs of hepatitis.
• Use same brand and take at same time.
• Avoid high-fat diet
• Avoid excessive alcohol
• Inform dentist
• Vitamin K foods – avoid changing levels in diet.

Question 10

pregnancy category?

Answer 10

Pregnancy Category X - Drug has been shown to produce numerous fetal abnormalities, induce fatal bleeding, and can cause fetal death. Believed to be safe for lactating women who are at risk for postpartum venous thrombus because very little of the drug enters breast milk.

Question 11

Drug Interactions

Answer 11

Drug-drug interactions are numerous. Therapeutic index of warfarin is VERY low, drugs that interact with warfarin have the potential to affect coagulation time and cause harm.

• Concurrent use with other drugs with anticoagulant activity may produce additive effects and excessive bleeding.
• Extensive protein-binding is responsible for numerous drug-drug interactions including NSAIDs (cause an increase bleeding risk), diuretics, SSRIs, other antidepressants, steroids, antibiotics, vitamins, and vaccines.
• Green tea, gingko, feverfew, garlic, cranberry, chamomile, and ginger may increase the risk of bleeding.