Duration of treatment.

• Deep vein thrombosis (DVT): 6 - 8 weeks

Except in pregnancy, or if there is another reason for prolonged treatment.

• Pulmonary embolism (PE): 3 months

• Atrial fibrillation: life long treatment.

• Heart valve prostheses: life long treatment.

Heparin Treatment

Prophylaxis against DVT

following surgery and immobility e.g cardiac failure:

Heparin (SC) 5000 units every 8 hours until ambulant.

Treatment of DVT/PE

Heparin (IV) 10000 units every 6 hours.

Monitor APTT - aim for 2-3 times control.
Continue until warfarin is effective, usually 3-5 days.

If facilities for monitoring APTT and INR are not available, DVT, may be treated with:

Heparin (SC) 10000 units twice daily for 3 - 4 weeks.

DVT in pregnancy

Continue throughout pregnancy, aiming for APTT 2-3 times normal:

Heparin (SC) 10000 units twice daily;

OR

Warfarin after first trimester (12 weeks) keeping INR in the range 2-3. At 32-34 weeks stop Warfarin and change to Heparin as above.

Heparin Overdosage

If bleeding occurs, stop heparin and give:

Protamine sulphate (slow IV) 1 mg neutralises 100 units of Heparin. Maximum dose 50 mg (in excess protamine is also an anticoagulant).

Oral Anticoagulation

Warfarin (O) loading dose 10 mg once daily for 2 days. Check INR on 3rd day and dose accordingly. The drug should be taken at the same time each day.

Therapeutic Range for Warfarin use

DVT/PE: INR 2-3, heart valve prosthesis: INR 3-4.5.

There is great individual variation in dose (average daily dose 3-9 mg). Monitor INR regularly, initially daily/ alternate days then increase interval gradually to a maximum of 8 weeks. Reduce loading dose in elderly and in patients with renal/ hepatic impairment.

Drugs Interacting with Warfarin

Below are a few examples:

Warfarin Overdosage:

If INR 4.5-7 without haemorrhage - withhold Warfarin for 1-2 days then review.

If INR > 7 without haemorrhage - withhold Warfarin and check INR daily.

Consider giving:

Vitamin K (slow IV) 0.5-1 mg injection (not IM).

If INR > 4.5 with haemorrhage, give:

Fresh frozen plasma (FFP) 2-4 bags, then check INR and repeat infusion if bleeding continues.

Plus

Vitamin K (slow IV) 0.5 - 1 mg (higher doses Vitamin K will prevent adequate anticoagulation for up to 2 weeks).

Streptokinase Treatment

Life Threatening Pulmonary Embolism / Arterial Embolism

Streptokinase (IV) loading dose of 250000 units over 30 minutes, then 100000 units every hour for 24-72 hours