Low molecular weight heparin: Difference between revisions

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==Background==
==Background==
#Similar mechanism of action as heparin but with predictable effect
*Class of [[anticoagulant]] medications.
#Advantages over unfractionated heparin:
*Defined as heparin salts having an average molecular weight of less than 8000 Dalton
##More reliable level of anticoagulation
*LMWHs inhibit the coagulation process through binding to antithrombin which in turn inhibits activated factor X.<ref>Garcia DA, Baglin TP, Weitz JI, et al. (2012). "Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines"</ref>
##No need for monitoring w/ PTT
*LMWH therapy is monitored by the anti-factor Xa assay (measures anti-factor Xa activity).
##Decreased incidence of HIT
**Cannot be acceptably measured using the partial thromboplastin time (PTT) or activated clotting time (ACT) tests.
##Can give as oupt
#Disadvantages compared to unfractionated heparin:
##Renally excreted; may accumulate in pts w/ renal impairment leading to bleeding
##Longer half-life


==Dosing==
==Types==
#Renal impairment (Cr clearance <30)
{| class="wikitable"
##Use 50% of usual dose or use UFH instead
|-
#Obesity
! LMWH !! Average molecular weight !! Ratio anti-Xa/anti-IIa activity
##Weight-based dosing safe up to 190kg (no data available thereafter)
|-
| [[Bemiparin]] || 3600 || 8.0
|-
| [[Nadroparin]] || 4300 || 3.3
|-
| [[Reviparin]] || 4400 || 4.2
|-
| [[Enoxaparin]] (Lovenox) || 4500 || 3.9
|-
| [[Parnaparin]] || 5000 || 2.3
|-
| [[Certoparin]] || 5400 || 2.4
|-
| [[Dalteparin]] || 5000 || 2.5
|-
| [[Tinzaparin]] || 6500 || 1.6
|-
|}


==Treatment==
==Clinical Differences from [[Unfractionated heparin]]==
#See:
*Less frequent subcutaneous dosing
##[[DVT]]
*Once or twice daily subcutaneous injection for treatment of venous thromboembolism and in unstable angina instead of intravenous infusion of high dose heparin.
##[[PE]]
*No need for monitoring of the aPTT coagulation parameter as required for high dose heparin.<ref>http://chestjournal.chestpubs.org/content/119/1_suppl/64S.full</ref>
##[[NSTEMI]]
*Possibly a smaller risk of bleeding
##[[STEMI]]
*Smaller risk of osteoporosis in long-term use.
*Smaller risk of [[Heparin-Induced Thrombocytopenia (HIT)|heparin-induced thrombocytopenia]], a potential side effect of [[Unfractionated heparin|heparin]].
*The anticoagulant effects of heparin are typically reversible with [[Protamine sulfate|protamine sulfate]], while protamine's effect on LMWH is limited.


==Complications==
==Indications==
#Bleeding
*[[Deep venous thrombosis]]
##Less common than with UFH
*[[Pulmonary embolism]]
##Treatment
*[[Non ST-Elevation Myocardial Infarction (NSTEMI)]]
###Protamine
*[[ST-segment elevation myocardial infarction (STEMI)]]
####Does not completely reverse LMWHs
*[[Stroke (main)]]
####Carries significant anaphylaxis risk (0.2%); only use for major bleeding
####Dosing
#####For Enoxaparin: protamine 1mg IV for every 1mg of enoxaparin given in previous 8h
######If 8–12h since last enoxaparin dose give 0.5mg IV for every 1mg of enoxaparin given
#Pruritus
##Local skin reaction


==See Also==
==See Also==
*[[Heparin (Unfractionated)]]
*[[Coagulopathy (main)]]
*[[Unfractionated heparin]]


==Source ==
==References==
Tintinalli
<references/>


[[Category:Drugs]]
[[Category:Pharmacology]]
[[Category:Heme/Onc]]
[[Category:Heme/Onc]]

Latest revision as of 17:28, 19 September 2019

Background

  • Class of anticoagulant medications.
  • Defined as heparin salts having an average molecular weight of less than 8000 Dalton
  • LMWHs inhibit the coagulation process through binding to antithrombin which in turn inhibits activated factor X.[1]
  • LMWH therapy is monitored by the anti-factor Xa assay (measures anti-factor Xa activity).
    • Cannot be acceptably measured using the partial thromboplastin time (PTT) or activated clotting time (ACT) tests.

Types

LMWH Average molecular weight Ratio anti-Xa/anti-IIa activity
Bemiparin 3600 8.0
Nadroparin 4300 3.3
Reviparin 4400 4.2
Enoxaparin (Lovenox) 4500 3.9
Parnaparin 5000 2.3
Certoparin 5400 2.4
Dalteparin 5000 2.5
Tinzaparin 6500 1.6

Clinical Differences from Unfractionated heparin

  • Less frequent subcutaneous dosing
  • Once or twice daily subcutaneous injection for treatment of venous thromboembolism and in unstable angina instead of intravenous infusion of high dose heparin.
  • No need for monitoring of the aPTT coagulation parameter as required for high dose heparin.[2]
  • Possibly a smaller risk of bleeding
  • Smaller risk of osteoporosis in long-term use.
  • Smaller risk of heparin-induced thrombocytopenia, a potential side effect of heparin.
  • The anticoagulant effects of heparin are typically reversible with protamine sulfate, while protamine's effect on LMWH is limited.

Indications

See Also

References

  1. ↑ Garcia DA, Baglin TP, Weitz JI, et al. (2012). "Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines"
  2. ↑ http://chestjournal.chestpubs.org/content/119/1_suppl/64S.full
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