September 26, 2022

Unfractioned Heparin and Low Molecular Weight Heparins

  • March 28, 2011
  • 2 min read
Unfractioned Heparin and Low Molecular Weight Heparins

Unfractioned Heparin-

Unfractioned Heparin- is derived from  porcine intestinal mucosa or bovine lung tissue. UFH catalyzises that inactivation of thrombin and factor Xa by inhibiting Anti-thrombin III.  At usual dose it prolongs TT and aPTT and has a minimal effect on PT/INR.

Benefits of UFH-

  1. 1. The effect of UFH normalizes within hours of discontinuation
  2. 2. It is reversible with Protamine Sulphate.
  3. 3. Can be titrated according to aPTT.
  4. 4. Dosing is not typically affected by Renal function.


1. DVT prophylaxis- 5000 U SC  Q8-Q12hrly ( aPTT monitoring not necessary)

2. Therapeutic anticoagulation

a. Weight based Heparin dosing-

Bolus- 80 U/kg

Infusion- 18U/kg/hr.



aPTTDose Modification
<4080U/kg bolus, increase infusion by 3 U/kg/hr
40-5040U/kg bolus, increase infusion by 2 U/kg/hr
50-59Increase infusion by 1 U/kg/hr
60-94No change
95-104Decrease infusion by 1U/kg/hr
105-114Hold for 30 min and decrease infusion by 2 U/kg/hr
>115Hold for 1 hr, decrease infusion by 3 U/kg/hr

aPTT target level may vary depending upon the Hospital standards.

aPTT to be sent 6 hrly after any bolus or dose change.


b. For Acute STEMI patients-

60U/kg bolus ( usually 5000U bolus) followed by 12U/kg/hr(  usu. 1000U/kg/hr)

Dose-adjusted UFH may be administered SC q8hrly ( 12000U UFH) or Q12hr ( 16000U UFH) à  aPTT after 6 hrs.


2. Low-Molecular Heparin-

Produced by chemical and enzymatic cleavage of UFH.  LMW inactivates factor Xa to greater extent. It minimally prolongs aPTT.

Caution required in patients with deranged RFT, obesity, pregnancy—facter Xa assay may be needed.

These are only partially reversible with Protamine.

EnoxaparinOutpatient- 1mg/kg SC Q12hr

Inpatient- 1mg/kg SC Q12hr or 1.5mg/kg SC Q24hr

Tinzaparin175 IU/kg SC daily
Dalteparin200 IU/kg SC daily
Fondaparinux5 mg SC daily for weight <50 kg, 7.5mg SC daily for weight 50-100kg, and 10 mg SC daily for weight >100kg

Caution: If RFT is deranged.


Lepirudin ( Refludan, recombinant hirudin) – direct thrombin inhibitor that is used for treatment of HIT.( Heparin Induced Thrombocytopenia )


By Dr Sujit Shrestha ( Reference – various sources including Washington manual, internet)

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