Heparins and Fondaparinux Flashcards
What are the two most common indications for heparins and fondaparinux?
VTE and ACS.
LMWH is the first-choice agent in pharmacological VTE prophylaxis in hospital patients and for initial treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE).
In ACS, LMWH or fondaparinux are part of first-line therapy to improve revascularisation and prevent intracoronary thrombus progression.
What is fondaparinux?
Fondaparinux is a synthetic a compound that is similar to heparin, it inhibits Factor Xa only with similar efficacy to LMWH.
It is the anticoagulant of choice in the treatment of ACS in many hospitals in the UK.
Forms part of first-line therapy in ACS to improve revascularisation and prevent intracoronay thrombus progression.
How does fondaparinux work?
It inhibits Factor Xa only with similar efficacy to LMWH.
Factor Xa is a key component in the final common coagulation pathway.
How do LMWH such as dalteparin and enoxaparin function?
They preferentially inhibit factor Xa - they have a more predictable effect than UFH and do not usually require laboratory monitoring.
What are the most common side effects of LMWH, UFH, fondaparinux etc?
Bleeding. Injection site reactions.
Heparin-induced thrombocytopenia: a dangerous syndrome characterised by low platelet count and thrombosis. This immune reaction is less likely with LMWH and fondaparinux than with UFH.
What are the contraindications to the use of LMWH and fondaparinux?
Clotting disorders, severe uncontrolled hypertension or recent surgery or trauma. Only use with caution in these patients.
In patients with renal impairment, LMWH and fondaparinux may accumulate and should be used at a loer dose of use UFH instead.
In major bleeding associated with heparin therapy, what can be given to reverse anticoagulation? When is this ineffective?
Protamine can be give, this is effective for UFH but less so for LMWH and totally ineffective against fondaparinux.
When would LMWH and warfarin be used at the same time?
Initially while initiating warfarin therapy.
High doses of LMWH and fondaparinux are commonly seen when?
In the treatment of VTE and ACS.
Low doses of LMWH and fondaprinux are commonly used when?
Prophylaxis doses for VTE
Where should SC injections of LMWH and Fondaparinux be given? Why?
LMWH + fondaparinux etc should be given SC into the abdominal wall.
The arm should not be used because this can cause uncomfortable and disabling bruising.
What measurement is used for the anticoagulant effect of UFH?
The activated partial thromboplastin ratio (APTR), it is measured frequently (every 6 hours initially) during an infusion of UFH. The target APTR is 1.5-2.5.
During an infusion of UFH, what is the target APTR?
1.5-2.5,
When would LMWH activity be monitored? How?
In pregnancy, using anti-Xa activity.
Following a new diagnosis of VTE, patients will often initially be treated with LMWH and warfarin, why?
This is because warfarin inhibits the natutal anticoagulant activity of proteins S and C, and it does this before inhibiting the other clotting factors.
Using LMWH provides anticoagulant cover during this initial pro-coagulant period. LMWH is stopped when the patients INR is in therapeutic range.
