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.
CAUTION Warfarin may harm the foetus and should not be used under 12 weeks. Monitor closely whichever method is used. Specialist supervision is recommended. |
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
CAUTION Drug interactions are common and can be dangerous |
Below are a few examples:
Warfarin Inhibition |
Warfarin Potentiation |
Barbiturates |
Alcohol |
Oral contraceptives |
Chloramphenicol |
Griseofulvin |
Cimetidine |
Rifampicin |
Erythromycin |
Carbamazepine |
Co-trimoxazole |
Vitamin K |
Acetylsalicylic acid |
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
CAUTION allergic reactions may occur - before infusion give: hydrocortisone (IV) 100 mg. |
