Warfarin (or) Coumadin

Warfarin has a long half-life (i.e. 40 hours) therefore higher loading doses are required if a pharmacological effect is required quickly.

Phytomenadione (Vitamin K) and Menadiol Sodium phosphate (water soluble synthetic Vitamin K derivate) antagonises the effects of warfarin.

Contraindications

• Hypersensitivity
• Haemorrhagic stroke
• Clinically significant bleeding
• Pregnancy ( especially during the first and third trimester)
• Severe liver disease
• Severe renal impairment
• Within 72 hours of major surgery with severe risk of bleeding
• Within 48 hours postpartum

Warfarin is administered orally and metabolised in the liver by Cytochrome P450 enzymes.

Increased INR

• Antiarrhythmics e.g. Amiodarone
• Antibacterials e.g. cephalosporins, ciprofloxacin, levofloxacin, macrolides, tetracyclines and trimethoprim
• Antidepressants e.g. SSRIs, Venlafaxine and Mirtazepine
• Antiplatelets e.g. Aspirin and Clopidogrel
• Azole antifungals e.g. Fluconazole and Miconazole