Warfarin Administration Route
Warfarin is administered orally, not intravenously. 1
Pharmacokinetics and Absorption
- Warfarin is essentially completely absorbed after oral administration, with peak concentrations generally attained within the first 4 hours. 1
- The oral formulation demonstrates complete bioavailability, making intravenous administration unnecessary for therapeutic anticoagulation. 1
- After oral administration, warfarin distributes into a relatively small apparent volume of distribution of approximately 0.14 liter/kg. 1
Clinical Context from Guidelines
- All major guidelines consistently refer to warfarin as an oral anticoagulant that is initiated orally alongside heparin therapy. 2
- The European Society of Cardiology guidelines specify that "oral anticoagulants in current use in Europe are sodium warfarin, acenocoumarol and fluindione," emphasizing the oral route as standard. 2
- When initiating warfarin therapy, guidelines recommend starting with the expected maintenance dose orally (5 mg daily for warfarin) on the first or second day of heparin treatment. 2
Reversal Situations
- The only time intravenous administration is mentioned in warfarin management is for vitamin K administration (not warfarin itself) when rapid reversal of anticoagulation is needed for serious bleeding or emergency surgery. 2, 3, 4
- For life-threatening bleeding, vitamin K 5-10 mg is given by slow intravenous infusion over 30 minutes to reverse warfarin's effects. 2, 4
Practical Considerations
- Warfarin tablets are well absorbed in the gut and transported in plasma highly bound to albumin (97-99%). 2
- The oral route is preferred because it is convenient, safe, and provides predictable therapeutic effects when properly monitored. 2
- There is no clinical indication for intravenous warfarin administration in standard practice. 1