Warfarin

• is indicated for valvular AF
• Start ~5mg orally, daily
• Target INR: 2.0-3

Contraindications to warfarin therapy

• Absolute contraindications to warfarin therapy include:
  • known large oesophageal varices
  • significant thrombocytopenia (platelet count less than 50 x 109/L)
  • within 72 hours of major surgery with risk of severe bleeding – defer and reassess post-operatively
  • previously documented hypersensitivity (e.g. priapism or ischaemic necrosis)
  • acute clinically significant bleed – defer and reassess stroke versus bleeding risk within three months
  • decompensated liver disease or deranged baseline clotting screen (initial INR greater than 1.5)
  • pregnancy and within 48 hours postpartum. Warfarin is teratogenic and can cause foetal bleeding.

• Relative contraindications to warfarin therapy include:
  • previous history of intracranial haemorrhage – seek specialist opinion
  • recent major extracranial bleed within the last six months where the cause has not been identified or treated – defer the decision for warfarin therapy
  • peptic ulcer within last three months – defer until peptic ulcer treatment completed. Ensure peptic ulcer preventative therapy is initiated whilst on anticoagulant
  • recent history of recurrent falls in patient at higher risk of bleeding (i.e. HAS-BLED score greater than or equal to 3)
  • Guidelines for warfarin management in the community – 6 – dementia or marked cognitive impairment with poor medicines adherence and no carer support
  • chronic alcohol abuse, especially if binge drinking
  • untreated or poorly controlled hypertension, consistently greater than 160/9 mm/Hg.

Factors that influence the INR

•  In assessing potential drug interactions, consider all concomitant therapy including herbal/complementary and over-the-counter medications.
• Dramatic changes in diet can affect the INR due to varying vitamin K levels within different foods (e.g. green leafy vegetables are high in vitamin K).
• Altered health status (e.g. acute illness or worsening chronic renal or hepatic impairment) may alter response to warfarin due to effects on the synthesis of clotting factors or changed metabolism of warfarin

Advice on Managing Bleeding Risk

1. Regular Monitoring:
   • INR Checks: Adhere to regular INR monitoring to ensure levels remain within the therapeutic range.
   • Routine Assessments: Regular check-ups with your healthcare provider to assess for any signs of bleeding or other complications.
2. Medication Adherence:
   • Consistent Dosing: Take warfarin exactly as prescribed. Do not skip doses or take double doses.
   • Report Other Medications: Always inform your healthcare provider about all other medications, including over-the-counter drugs and supplements, as many can interact with warfarin and increase bleeding risk.
     • Antibiotics: Some antibiotics can increase INR by reducing vitamin K-producing gut flora.
     • Antifungals: Drugs like fluconazole can increase INR.
     • Antiarrhythmics: Amiodarone can significantly elevate INR.
     • Analgesics: NSAIDs and acetaminophen can affect INR levels.
     • Antiplatelet agents: Aspirin and clopidogrel can increase bleeding risk when combined with warfarin.
     • Other Medications: Many other medications, including certain antidepressants and anticonvulsants, can affect INR.
3. Dietary Considerations:
   • Vitamin K Intake: Foods high in vitamin K (e.g., leafy green vegetables, broccoli, Brussels sprouts) can lower INR.
   • Consistency of Diet: Fluctuations in vitamin K intake can lead to unstable INR levels.
4. Lifestyle Factors:
   • Alcohol Consumption: Excessive alcohol can affect INR by interfering with liver function and warfarin metabolism.
   • Smoking: Can lower INR by inducing the metabolism of warfarin.
5. Injury Prevention:
   • Avoid High-Risk Activities: Engage in activities with a low risk of trauma or injury. Avoid contact sports or activities with a high risk of falls.
   • Use Protective Gear: When engaging in necessary physical activities, use appropriate protective gear to reduce the risk of injury.
6. Symptom Awareness:
   • Signs of Bleeding: Be vigilant for signs of bleeding, including:
     • Unusual bruising or bleeding
     • Prolonged bleeding from cuts
     • Blood in urine or stool
     • Black or tarry stools
     • Nosebleeds or bleeding gums
     • Coughing up blood or vomiting blood
     • Severe headache or dizziness
   • Immediate Action: Seek immediate medical attention if you experience any signs of significant bleeding or if you sustain an injury.
7. Health Management:
   • Manage Other Health Conditions: Conditions like liver disease, kidney disease, and gastrointestinal disorders can increase bleeding risk. Proper management of these conditions is essential.
   • Report Illnesses: Inform your healthcare provider if you develop any illnesses or infections, as these can affect warfarin metabolism and increase bleeding risk.
8. Emergency Planning:
   • Carry Medical Information: Always carry identification that indicates you are on anticoagulant therapy. Consider wearing a medical alert bracelet.
   • Emergency Contacts: Keep a list of emergency contacts and your healthcare provider’s information readily available.
9. Educate and Communicate:
   • Patient Education: Understand the importance of managing bleeding risk and know how to identify signs of bleeding.
   • Open Communication: Maintain open communication with your healthcare provider. Report any changes in your health, new medications, or any concerns promptly.

Specific Situations

1. Dental Procedures: Inform your dentist that you are on warfarin. Some dental procedures may require adjustments to your medication.
2. Surgery or Invasive Procedures: Notify your healthcare provider before any surgery or invasive procedures, as you may need to temporarily adjust your warfarin dose.
3. Travel: Plan ahead when traveling. Ensure you have enough medication, and know where you can get your INR checked if needed.

 

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