Starting
treatment
Indications
Dosing
and monitoring
Complications
Follow-up
|  | | | Dosing
and monitoring |
Give the warfarin at 5 to 6 pm, and measure the INR at 9 am the next day.
Monitor INR daily until in range and stable.
Warfarin dosing regimen to achieve INR 2.0 to 3.0 b 
|
Dose for age (mg)
|
| Day |
INR |
up to 50 |
51 to 65 |
66 to 80 |
> 80 |
| 1 |
<1.4 |
10 |
9 |
7.5 |
6 |
|
|
|
|
|
|
| 2 |
<1.6 |
10 |
9 |
7.5 |
6 |
|
> 1.6 |
0.5 |
0.5 |
0.5 |
0.5 |
|
|
|
|
|
|
| 3 |
<1.8 |
10 |
9 |
7.5 |
6 |
|
1.8 to 2.5 |
4.0 to 5.0 |
3.5 to 4.5 |
3.0 to 4.0 |
2.5 to 3.0 |
|
2.6 to 3.0 |
2.5 to 3.5 |
2.5 to 3.5 |
2.0 to 2.5 |
1.5 to 2.0 |
|
3.1 to 3.5 |
1.0 to 2.0 |
1.0 to 2.0 |
0.5 to 1.5 |
0.5 to 1.5 |
|
3.6 to 4.0 |
0.5 |
0.5 |
0.5 |
0 |
|
> 4.0 |
0 |
0 |
0 |
0 |
|
|
|
|
|
|
| 4 |
< 1.6 |
10.0 to 15.0 |
9.0 to 13.0 |
7.5 to 11.0 |
6.0 to 9.0 |
|
1.6 to 1.9 |
6.0 to 8.0 |
5.5 to 7.0 |
4.5 to 6.0 |
3.5 to 5.0 |
|
2.0 to 2.6 |
4.5 to 5.5 |
4.0 to 5.0 |
3.5 to 4.5 |
2.5 to 3.5 |
|
2.7 to 3.5 |
3.5 to 4.0 |
3.0 to 3.5 |
2.5 to 3.0 |
2.0 to 2.5 |
|
3.6 to 4.0 |
3 |
2.5 |
2 |
1.5 |
|
4.1 to 4.5 |
omit next day's dose,
then 1.0 to 2.0 |
omit next day's dose,
then 1.0 to 2.0 |
omit next day's dose,
then 1.0 to 2.0 |
omit next day's dose,
then 1.0 to 2.0 |
|
> 4.5 |
nil: hold dose |
nil: hold dose |
nil: hold dose |
nil: hold dose |
Decrease the dose by 33% if
the patient has one or more of the following risk factors:
-
Severe
congestive heart failure (ejection fraction < 30% and/or
biventricular failure)
-
Severe chronic
obstructive airways disease (oxygen or steroid use or dyspnoea at
rest)
-
Concurrent
amiodarone use.
Why?
- Patients loaded with an age-adjusted warfarin regimen compared with
Fennerty's regimen
are less likely to have a dose withheld or an INR of 4.0 or more. b
- A stable INR is more likely after a week on the age-adjusted
regimen. b
An age-adjusted regimen leads to safer loading
than Fennerty's regimen.
| Patient |
Treatment |
Comparison |
Outcome |
CER |
RRR
(95% CI) |
NNT
(95% CI) |
|
proximal DVT b
|
age-adjusted regimen
|
Fennerty's regimen
|
warfarin dose withheld
at 8 days
|
39%
|
85%
(40% to 96%)
|
3
(2 to 7)
|
|
|
|
|
INR 4.0 or more
at 7 days
|
32%
|
82%
(24% to 96%)
|
4
(2 to 13)
|
|
internal medicine