2913056
Description
Flashcards by jenny schneider, updated more than 1 year ago
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Created by jenny schneider
over 9 years ago
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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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