Anti-coagulants Flashcards
How does warfarin work?
It prevents vitamin K being reduced to it’s active form, decreasing prothrombin, factor VII, IX and X synthesis.
What are DDIs of warfarin?
GI bleeds, epistaxis, bruising and intracranial haemorrhage.
How can warfarin be reversed?
Vitamin K intravenously given, or fresh frozen plasma.
What DDIs increase warfarin’s effects?
CYP450 Inhibitors, Cephalosporin Antibiotics (destroy flora which help vit K absorption), protein displacers, and aspirin (platelet effect).
What DDIs decrease warfarin action?
CYP inducers.
What effects can warfarin have in different trimesters of pregnancy?
Teratogenesis in 1st trimester, and intracranila haemorrhage in 3rd trimester.
How many day’s offset are required for warfarin to be cleared before surgery?
3 days
How does heparin work?
Binds (as agonist) to antithrombin III, which inactivates factors IIa, Xa, V, VII, IX and XI as unfractioned heparin, and only Xa as LMWH.
What two types of heparin are there and compare their routes of delivery and pharmacokinetics
Unfractioned heparin, which is given intravenously, and has non-linear pharmacokinetics. Low molecular weight heparin which is given orally or subcutaneously and has linear pharmacokinetics and a steady 90% oral bioavailability.
How is heparin monitored?
Activated Partial Thromboplastin Time, a measure of the intrinsic pathway, that should be 30 -50 seconds.
When is heparin used?
Peri-operatively, whilst warfarin is loading, in ACS to prevent further thrombosis, and as a warfarin alternative in pregnancy.
What are some ADRs of heparin?
Epistaxis, bruising, intracranial haemorrhage, GI bleeds, and heparin induced thrombocytopenia (AI reaction to heparin on platelets).
What are some contraindications for heparin?
Peptic ulcer disease, haemophilia and thrombocytopenia.
How is heparin reversed?
Protamine sulfate
How is warfarin monitored?
With International Normalised Ratio, a measure of prothrombin time/ extrinsic pathway function. It should be between 2 and 3.
When is Dipyridamole given?
As a warfarin adjuvant in prosthetic heart valves.
How does dipyridamole work?
Inhibits phosphodiesterase, which increases cAMP and calcium, blocking the platelet response.
What are some ADRs of dipyridamole?
Headache, diarrhoea and hypotension.
When is Clopridogel given?
As an anti-platelet for prevention of secondary stroke or MI, or for patients with aspirin allergies.
How does clopridogel work?
Antagonises platelet ADP receptors, preventing platelet activation.
What are some ADRs of clopridogel?
Haemorrhage, rash and neutropenia.
Name a Glycoprotein IIb/IIIa inhibitor and it’s route of administration?
Abciximab, given intravenously.
When is Abciximab given?
For short-term prevention of MI in unstable angina, due to it’s 10 minute half-life.
How does abciximab work?
Binds to platelet glycoprotein IIb/IIIa receptors, antagonises them and reduces platelet aggregation.
How does streptokinase work, how is it given, and when is it used?
Streptokinase forms a complex with, and activates plasminogen to plasmin, starting fibrinolysis. It is given intravenously in life threatening thromosis or embolism events.
What are contraindications for streptokinase or tissue plasminogen activator use?
Recent haemorrhage, trauma, surgery, aortic dissection, cerebrovascular history, hypertesnion, previous streptokinase use (streptokinase is produced from cocci, use a second time causes anaphylaxis), and peptic ulcer disease.
What are 2 ADRs of streptokinase and tissue plasminogen activators?
Hypotension and haemorrhage.
Name two intravenous tissue plasminogen activators
Alteplase and Reteplase.
When are tissue plasminogen activators used?
In MI or pulmonary embolism.
How do tissue plasminogen activators work?
Converts plasminogen to plasmin, initiating fibrinolysis.
