Anti-coagulants Flashcards
What is the action of Warfarin ?
Warfarin, a coumarin derivative acts by reversibly inhibiting the enzyme vitamin K epoxide reductase which is responsible for gamma-glutamyl carboxylation of the simogenes such as factors II, VII, IX, X, proteins C and S leading to anti-coagulation.
What are the indications of warfarin in cardiology ?
The three most common indications for warfarin therapy are;
* atrial fibrillation (AF)
* venous thromboemolism (VTE)
* prosthetic heart valves.
What are the contraindications for Warfarin ?
Active ulceration or overt bleeding of the gastrointestinal, genitourinary, or respiratory tract. Central nervous system hemorrhage and pregnancy. Advanced age, recurrent falls.
What is the pharmacokientics of Warfarin ?
It is fully absorbed and reaches maximum plasma concentration within 2-6 hrs. It has a half-life of ~35 Hrs and is eliminated by hepatic metabolism with a very small clearance (0.2 L/h/70kg).
What is the pharmacodynamics of Heparin ?
It is a heterogenous mixture of polysaccharide chains with the molecular weight ranging from 3000-30,000 D. It acts by inducing conformational changes to the anti-coagulant enzyme antithrombin III. Binding of Heparin to AT-III results in 10,000 fold amplification of the AT-III’s ability to inhibit thrombin (F IIa), IXa, Xa, XIa, and XIIa.
What are the indications for Unfractioned heparin ?
Unfractionated heparin is indicated for both the prevention and treatment of thrombotic events such as DVT, PE and AF.
How to monitor unfractioned heparin therapy ?
Activated partial thromboplastin time (aPTT) and anti-Xa activity.
What is the pharmacokinetics of unfractioned heparin ?
It is administered as continuous IV infusion or intermittent subcutaneous injection and has a half life of 1.5 hrs. The saturated unfractioned heparin is eliminated by the reticuloendothelial system and the unstaurated form is cleared by the kidneys.
What is the pharmacodynamics of LWHP?
LMWHs, in contrast, consist of only short chains of polysaccharide and the mean molecular weight is <8000 D. It acts by mainly inhibiting Factor Xa. Therefore, it is monitored using Anti-Xa instead of aPTT.
What are the advantages of LMWH ?
- It can be safely used in pregnant woman at risk of DVT.
- It doesn’t require regular monitorning.
- It is cheap and can be used in out-patient settings.
What is Direct oral anticoagulants (DOACS) therapy ?
It is a therapy consists of drugs that directly inhibit thrombin and Factor-Xa. They are used in the prevention of stroke for people with non-valvular AF.
What is the DOAC drug for thrombin inhibition ?
Dabigatran: 300 mg taken as one 150 mg capsule twice daily.
What are the DOAC drug for Factor Xa inhibition?
Rivaroxaban: 20 mg once daily
Apixaban: 5 mg BD for one week.
Edoxaban: 60 mg / day.
What is the indication for D-dimer test ?
A positive D-Dimer test suggest the need for acute thrombosis work-up.
What are the indications for thrombolysis ?
ischemic stroke , MI,DVT, Massive pulmonary embolism, Acute limb ischaemia.
