Alternative protocol to start warfarin therapy: FENNERTY
Note this should only be used in patients with no risk factors.
We recommend a lower dose protocol.
Over the last few years the trend has been to use lower doses of Warfarin for initiating anticoagulant therapy. The standard Fennerty protocol was published in 1988. This was based on a study of patients with a mean age of 52 years. In recent years the trend has been to use Warfarin in older patients particularly with the increased use for atrial fibrillation. It is well recognised that some older patients are particularly sensitive to Warfarin.
Recent published reports have shown that a daily loading dose of 5mg for 3 or 4 days can be used safely as an outpatient anticoagulant regimen. With this approach less patients develop an INR above the therapeutic range during the first few days of treatment. As a result daily INR monitoring may not be required. This low dose regimen has been recommended for starting Warfarin therapy in patients with atrial fibrillation. Published reports have shown that the time taken to reach stable anticoagulant control is no longer using a low dose regimen than the standard Fennerty protocol.
Starting Warfarin
| Day |
INR* |
Warfarin dose (mg) |
| 1. |
< 1.4
|
10 |
| 2. |
< 1.8
1.8
> 1.8 |
10
1
0.5 |
| 3. |
< 2.0
2.0 - 2.1
2.2 - 2.3
2.4 - 2.5
2.6 - 2.7
2.8 - 2.9
3.0 - 3.1
3.2 - 3.3
3.4
3.5
3.6 - 4.0
> 4.0 |
10
1 5
4.5
4
3.5
3
2.5
2
1
1.5
0.5
0 |
| 4. |
< 1.4
1.4
1.5
1.6 - 1.7
1.8
1.9
2.0 - 2.1
2.2 - 2.3
2.4 - 2.6
2.7 - 3.0
3.1 - 3.5
3.6 - 4.0
4.1 - 4.5
> 4.5 |
> 8
8
7.5
7
6.5
6
5.5
5
4.5
4
3.5
3
Miss out next day's dose then give 2mg
Miss out 2 days doses then give 1 mg |
INR - International Normalized Ratio
APTT - activated partial thromboplastin time
*APTT should be within or below therapeutic range (1.5 - 2.5 x control). If APTT is above this range, the heparin effect on INR should be neutralised by adding protamine (0.4 mg / ml plasma) to the sample.
Reference:
Drug and Therapeutics Bulletin 1992; 30: 77 - 80
Fennerty A et al, Anticoagulants in venous thromboembolism. BMJ 1988; 297: 1285 - 8