A Warfarin Dosing Calculator is a specialized tool used by healthcare professionals to determine the appropriate dosage of warfarin for patients.
The calculator takes into account several factors, including:
- Patient’s current INR (International Normalized Ratio)
- Target INR range
- Current warfarin dose
- Patient-specific factors (age, weight, medical history)
For example, consider a patient with atrial fibrillation:
Current INR: 1.8
Target INR range: 2.0-3.0
Current warfarin dose: 5mg dailyWarfarin is an anticoagulant medication used to prevent blood clots in various conditions such as atrial fibrillation, deep vein thrombosis, and pulmonary embolism.
Warfarin Dosing Calculator
| Current Weekly Dose | Current INR | Target INR | New Weekly Dose | Conversion Equation |
|---|---|---|---|---|
| 35mg | 1.8 | 2.5 | 41.7mg | 35 × (1.8 / 2.5)^(-1.5) |
| 40mg | 3.2 | 2.5 | 35.4mg | 40 × (3.2 / 2.5)^(-1.5) |
| 28mg | 1.6 | 2.0 | 32.1mg | 28 × (1.6 / 2.0)^(-1.5) |
| 50mg | 3.8 | 3.0 | 42.6mg | 50 × (3.8 / 3.0)^(-1.5) |
| 45mg | 2.7 | 2.5 | 43.3mg | 45 × (2.7 / 2.5)^(-1.5) |
Warfarin Dosing Formula
The Warfarin Dosing Formula is based on the relationship between INR changes and dose adjustments.
New Weekly Dose = Current Weekly Dose × (Current INR / Target INR)^(-1.5)
Example:
- Current weekly dose: 35mg (5mg daily)
- Current INR: 1.8
- Target INR: 2.5
New Weekly Dose = 35 × (1.8 / 2.5)^(-1.5) ≈ 41.7mg
This suggests increasing the weekly dose to approximately 42mg, or 6mg daily.
How do I adjust my INR dosing?
General guidelines include:
- Small adjustments: Typically 5-20% of the total weekly dose
- Frequency: Check INR 4-7 days after dose changes
- Consistency: Maintain consistent dietary vitamin K intake
Remember, never adjust your warfarin dose without consulting your healthcare provider.
Warfarin Dosage Chart
| INR Range | Dose Adjustment |
|---|---|
| < 1.5 | Increase by 15-20% |
| 1.5-1.9 | Increase by 5-10% |
| 2.0-3.0 | No change (if within target) |
| 3.1-3.9 | Decrease by 5-10% |
| 4.0-4.9 | Hold 1-2 doses, then decrease by 10-15% |
| ≥ 5.0 | Hold dose, consider vitamin K, recheck INR |
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