protocol for warfarin anticoagulation

Dosage

Initiation of warfarin

daily dose of warfarin (mg)

day	INR	mg (< 80 kg)	mg (> 80 kg)
1	< 1.5	5	7.5
-	> 1.5	off protocol	off protocol
2	< 1.5	5	7.5
-	1.5-1.9	2.5	5-7.5
-	2.0-2.5	0-.2.5	0-5
-	> 2.5	0	0
3	< 1.5	5-10	7.5
-	1.5-1.9	2.5-5	5-10
-	2.0-3.0	0-2.5	0-5
-	> 3.0	0	0
4	< 1.5	10	12.5-15
-	1.5-1.9	5-7.5	5-10
-	2.0-3.0	0-5	0-5
-	> 3.0	0	0-2.5
5	< 1.5	10	10-15
-	1.5-1.9	5-7.5	5-10
-	2.0-3.0	0-5	0-5
-	> 3.0	0	0
6	< 1.5	7.5-12.5	15
-	1.5-1.9	5-10	5-12.5
-	2.0-3.0	0-7.5	0-7.5
-	> 3.0	0	0-5

• For patient beginning warfarin therapy, INR testing should be done every daily for 1 week, then weekly until stable for 2 consecutive tests, every 2 weeks until stable for 2 consecutive tests, then every 3-4 weeks
  • Every 12 weeks may be sufficient

Management

• Maintenance of warfarin
  • Weekly dosage change for target INR

Current INR	1.5-2.0	2.0-3.0	2.5-3.0
< 1.5	i* 5-10%	i* 5-20%	i* 5-20%
-	(2 weeks)	(2 weeks)	(2 weeks)
1.5-2.0	-	i* 5-10%	i* 5-15%
-	(4 weeks)	(2 weeks)	(2 weeks)
2.0-2.5	d* 5-10%	-	i* 5-10%
-	(2 weeks)	(4 weeks)	(2 weeks)
2.5-3.0	d* 5-15%	-	-
-	(2 weeks)	(4 weeks)	(4 weeks)
3.0-3.5	d* 10-20%,	d* 5-10%	-
-	may hold dose	(2 weeks)	(4 weeks)
-	(2 weeks)	-	-
3.5-4.0	hold dose	d* 5-10%	d* 5-10%
-	d* 20-50%	may hold dose	(2 weeks)
-	(2 weeks)	(2 weeks)	-
4.0-6.0	hold 2-3 days	hold 1-2 days	may hold 1-2 days
-	d* 20-50%	d* 10-20%	d* 5-10%
-	(2 weeks)	(2 weeks)	(2 weeks)
6.0-9.0	hold warfarin, consider admission to hospital	-	-
> 9	hold warfarin, consider admission to hospital, administration of vitamin K*	-	-

i* increase dosage

d* decrease dosage

# retest INR within time specified

* vitamin K 2.5-5.0 mg PO if no significant bleeding; vitamin K 10 mg IV infusion if significant bleeding regardless of INR (if elevated)

* for serious bleeding, also administer fresh frozen plasma, prothrombin complex concentrate or recombinant factor VII in addition to vitamin K

• Solitary deviations in INR with a history of stable control may be retested within 2 weeks with a slight decrease in dosage for 1 day only, and only in the absence of an identifiable trend change.

• Identification & control of precipitating factors (i.e. change in diet, disease state, drugs) is necessary to achieve stable anticoagulation & if remediable may make a warfarin dosage change unnecessary.

• Statistical modeling suggests that, for optimal management of target INR of 2.0-3.0, warfarin dose should be changed when INRs are =< 1.7 or >= 3.3

• Older age & amiodarone use predictive of lower doses to achieve therapeutic levels.

More general terms

• pharmacology
• protocol

Additional terms

• anticoagulation
• warfarin (Coumadin, Panwarfin, Jantoven)