Anticoagulants- Part 1

jenny schneider
Flashcards by jenny schneider, updated more than 1 year ago
jenny schneider
Created by jenny schneider about 6 years ago
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anticoagulants part 1 phar2102

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Question Answer
Which of the following anticoagulants is used as an alternative in patient with HIT? heparin lmwh such as enoxaparin or dalteparin warfarin danaparoid Danaparoid
Explain how heparin is produced heparin is extracted from porcine intestinal mucosa or bovine lung
True or False: The MW of unfractionated heparin is between about 12000-16000Da True
Treu or False Heparin is a heterogeneous mix of glycosaminoglycans of variable length True
How does heparin work? Heparin inhibits Factor Xa and thrombin in a 1:1 ratio. It augments the effect of the natural anticoagulant antithrombin as it has a specific pentasaccharide sequence which binds to AT to produce conformational change which accelerates AT activity
True or False: To inactivate thrombin, heparin must form a ternary complex binding both AT and thrombin and only UFH with >18 saccharide units can do this True
By what routes do we administer heparin? Heparin is administered IV or SC not IM as it produces haematoma and erratic absorption if give IM. It cannot be administered orally as will breakdown in gut
Which of the following statements is incorrect? a. heparin is extensively bound to plasma proteins b. onset of action of IV heparin is immediate c. the half-life of UFH is independent of dose heparin half-life is dose-dependent. it ranges from 30-90min and may be significantly higher (150min) at higher doses
How is heparin eliminated from body? Heparin is eliminated by enzymatic degradation and renally. The enzymatic process can be saturated so at higher doses renal elimination predominates. This saturation causes the half-life of heparin to be dose dependent
Does unfractionated heparin require close monitoring and periodic dose adjustment? yes
Why should a heparin formulation containing benzyl alcohol not be used in premature babies benzyl alcohol is toxic and has been associated with deaths in premature neonates
Which of the following is used to flush cannula? heparin 5000u/mL heparinised normal saline (50U/5mL) heparin comes in a range of strengths and the heparinised saline is very weak and used to stop clotting in cannula
What drug is used to reverse the effect of heparin and how does it work? Protamine sulfate is used, it complexes with heparin
What is an adverse effect that results in drop in platelet count that can occur with heparin? Heparin induced thrombocytopenia (HIT)
Explain how LMWHs differ from heparin (UFH) - how are they made and in chemical structure how do they differ? LMWHs are obtained by chemical or enzymatic depolymerisation of heparin. The mean MW is around 5000Da compared to 12000-16000 Da we see for heparin. It is shorter length chains of glycosaminoglycans
What are two examples of LMWHS? dalteparin and enoxaparin
How is the anticoagulant effect of LMWHs produced and how does it differ from heparin (UFH)? effect is mediated by binding to AT (like heparin) but LMWHS differ in their relative inhibition of FXa and thrombin. LMWHs have a smaller chain and cannot form ternary complex with thrombin, so they have much greater effect on Factor Xa than thrombin
Can dalteparin and enoxaparin be interchanged clinically (i.e. swap patients between these two LMWHs)? They CANNOT be interchanged as each LMWH has different FXa:thrombin inhibition ratio and differences in pharmacokinetics
What are the advantages of LMWHs over heparin (UFH) SC bioavailability of LMWHs is greater than 90% (SCbioavailability of heparin is much lower and more variable) LMWHS have predictable anticoagulant response and do not require routine monitoring LMWHS have long half-life allowing once daily dosing LMWHS have less binding to plasma and cellular proteins- helping to produce more predictable response LMWHS have dose independent clearance LMWHS have lower incidience of HIT
Is the anticoagulant effect of LMWHS fully reversed by protamine sulphate? No, it is only partially reversed
True or False: LMWHs supplied in prefilled syringe must have the bubble in syringe expelled before use FALSE the bubble is designed to ensure that the full dose is delivered and should not be expelled
True or False The needles on the LMWH profiled syringes should be wiped with a swab before injection False: to enable ease of injection, the needles are coated with silicon
True or False: Danaparoid is a low molecular weight heparin False It is a low molecular weight heparinoid; it does not contain heparin or heparin fragments
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