Warfarin Induction Protocol for Outpatients

A guideline is intended to assist healthcare professionals in the choice of disease-specific treatments.

Clinical judgement should be exercised on the applicability of any guideline, influenced by individual patient characteristics. Clinicians should be mindful of the potential for harmful polypharmacy and increased susceptibility to adverse drug reactions in patients with multiple morbidities or frailty.

If, after discussion with the patient or carer, there are good reasons for not following a guideline, it is good practice to record these and communicate them to others involved in the care of the patient.

5mg Warfarin Induction Protocol for out-patients (Tait & Sefcick)

The regimen relies on checking a baseline INR as well as an INR on days 5 & 8 (ie. the days after the 4th and 7th doses of warfarin). All patients with baseline INR <1.4 are given 5mg/day for 4 days initially. The INR result on day 5 then determines the dose for days 5-7. The dose for day 8 and beyond (reading across the table from the dose given at day 5) is determined by the INR on day 8.

d5 INR dose (for d5-7)

d8 INR dose (from d8)

≤ 1.7

5mg

≤ 1.7

1.8 - 2.4

2.5 - 3.0

> 3.0

6mg

5mg

4mg

3mg for 4 days

1.8 - 2.2

4mg

≤ 1.7

1.8 - 2.4

2.5 - 3.0

3.1 - 3.5

> 3.5

5mg

4mg

3.5mg

3mg for 4 days

2.5mg for 4 days

2.3 - 2.7

3mg

≤ 1.7

1.8 - 2.4

2.5 - 3.0

3.1 - 3.5

> 3.5

4mg

3.5mg

3mg

2.5mg for 4 days

2mg for 4 days

2.8 - 3.2

2mg

≤ 1.7

1.8 - 2.4

2.5 - 3.0

3.1 - 3.5

> 3.5

3mg

2.5mg

2mg

1.5mg for 4 days

1mg for 4 days

3.3 - 3.7

1mg

≤ 1.7

1.8 - 2.4

2.5 - 3.0

3.1 - 3.5

> 3.5

2mg

1.5mg

1mg

0.5mg for 4 days

omit for 4 days

> 3.7

0mg

< 2.0

2.0 - 2.9

3.0 - 3.5

1.5mg for 4 days

1mg for 4 days

0.5mg for 4 days

At day 15 (or day 12) check INR and make fine dose adjustment as clinically appropriate.

2mg Warfarin Induction Protocol for out-patients (Oates et al.)

All patients are commenced on 2mg daily dose and INR is checked weekly. No alteration to dose is made within the first 2 weeks unless INR >4.0 or if INR <1.5 for 2 consecutive weeks.

Male

Female

INR at week 2

Maintenance dose (mg/day)

INR at week 2

Maintenance dose (mg/day)

1.0

1.1 – 1.2

1.3 – 1.5

1.6 – 2.1

2.2 – 3.0

>3.0

1.0 –1.1

1.2 – 1.3

1.4 – 1.9

2.0 – 3.0

>3.0