Day | INR | Dose when starting with 5 mg tablet | Dose when starting with 3 mg tablet* |
---|
- Usually INR stabilizes within 5-6 days in a stable clinical condition. Always aim at as even daily dosage as possible. Make dosage changes in small steps bearing in mind the slow pharmacokinetics of warfarin.
- If the dosage is difficult using either the 3 mg or 5 mg tablet strength, consider changing the tablet strength based on the weekly dose calculation.
- The need for a small dose is suggestive of slow metabolism. If the patient is at risk of bleeding, but the indication for warfarin is strong, a pharmacogenetic dosage prediction may be performed (see http://www.warfarindosing.org/).
- INR usually decreases by about one unit per day without a warfarin dose, except in slow metabolizers (small warfarin dose, e.g. < 1.5 mg per day).
* In primary health care, the starting dose should be 3 mg in small-sized and elderly patients, after thrombolytic therapy and in patients whose INR is spontaneously > 1.2, and the INR should be checked as early as on day 3
| |
1 | - | 5 mg | 3 mg |
2 | - | 5 mg | 3 mg |
3 | <2.0 | 5 mg | 3 mg |
2.0-2.4 | 5 mg | 3 mg |
2.5-2.9 | 2.5 mg | 1.5 mg |
3.0-3.4 | 2.5 mg | Omit the next dose or 1.5 mg |
3.5-4.0 | 1.5 mg (Note! Different tablet strength) | Omit the next dose |
>4.0 | Omit the next dose | Omit the next dose |
4-6 | <1.4 | 10 mg | 6 mg |
1.4-1.9 | 7.5 mg | 6 mg |
2.0-2.4 | 5 mg | 3 mg |
2.5-2.9 | 5 mg | 3 mg |
3.0-3.9 | 2.5 mg | 1.5 mg |
4.0-4.5 | Omit the next dose, then 1.5 mg (Note! Change to 3 mg tablet) | Omit the next dose, then 1.5 mg |
>4.5 | Omit the next 2 doses, then 1.5 mg (Note! Change to 3 mg tablet) | Omit the next 2 doses, then 1.5 mg |
Weekly dose based on INR value |
7- | 1.1-1.4 | Increase the weekly dose by 20% |
1.5-1.9 | Increase the weekly dose by 10% |
2.0-3.0 | Same weekly dose |
3.1-4.5 | Decrease the weekly dose by 10% |
>4.5 | Stop until INR < 4.5, restart with a 20% smaller weekly dose |