Anticoagulants Flashcards
What are anticoagulants used for
To prevent thrombus formation in veins
Anticoagulants include
Coumarins - phenindione and warfarin
DOACs
Can you use coumarins in pregnancy
No because it crosses the placenta- teratogenic - avoid!
Coumarins MOA
Antagonise vitamin K
Onset of coumarins is (how long they take to give full anticoagulation)
2-3 days
48-72 hours
A patient requires immediate effect of anticoagulation, what option would you give?
LMHW or unfractionated heparins have a quicker onset
Coumarins onset is 48-72 hours hence theyre not preferred in immediate onset requirement
Coumarins is required in a patient - drug of choice is ….
Warfarin
What are the different strengths of warfarin, what colours are their boxes
0.5 mg - white
1mg - brown
3mg - blue
5mg - pink
What colour box is 3mg warfarin
Blue
What colour box is 0.5 mg warfarin
White
What colour box is 1mg warfarin
Brown
What colour box is 5mg warfarin
Pink
Warfarin MHRA advice includes
Calciphylaxis
Miconazole interaction - daktarin oral gel
Describe miconazole (daktarin oral gel) and warfarin interaction.
Can you give them together?
Causes bleeding - seek medical advice if nose bleeds, blood in urine or unexplained bruising
Avoid unless patients INR is monitored closely
Describe calciphylaxis - where is this seen?
What action would you take if a patient presents to the pharmacy with this?
Painful rash
Its seen in patients taking warfarin especially if they are renally impaired
Refer to the GP
Warfarin antidote
Phytomenadiaone / vitamin K1
What foods are avoided with warfarin?
Cranberry juice
Pomegranate juice
Heavy alcohol - decreases effect of warfarin - inducer
Avoid diet change (liver, sprouts, broccoli, green tea, salads, leafy greens)
Cranberry and warfarin interaction
Cranberry juice increases anticoagulation affect of warfarin
Heavy alcohol interaction with warfarin
Heavy alcohol decreases the anticoagulation affect of warfarin
Warfarin in pregnancy, can it be given?
Avoid especially in 1st and 3rd trimester- risk if haemorrhage
What would you give a pregnant lady instead of warfarin?
LMWH
Tinazaparin, deltaparin, enoxeparin
INR can be within ……. Of target values when on warfarin
0.5
When is the required INR 3.5
Patients with recurrent DVT or PE
Patients with mechanical prosthetic heart valves
INR can be within 0.5 of target hence 3 or 4
Patient on warfarin for treatment of DVT or PE INR target
2.5
Patient on warfarin for recurrent DVT or PE target
3.5
Patient on warfarin for AF INR target
2.5
Patient on warfarin for Cardioversion INR target
2.5
Patient on warfarin for Mechanical prosthetic heart valve INR target
3.5
Patient on warfarin for Dilated cardiomyopathy INR target
2.5
Patient on warfarin for Mitral stenosis or regurgitation INR target
2.5
Patient on warfarin for Myocardial infarction INR target
2.5
Patient on warfarin for Acute arterial embolism INR target
2.5
A patient is on warfarin and has an INR of 5-8 with no bleeding, what do you do?
Withhold 1 or 2 doses of warfarin
Reduce subsequent maintenance dose
A patient on warfarin has an INR 5-8 with minor bleeding
Stop warfarin
Give phytomenadione/vit K1 slow IV injection
Restart when INR <5
A patient on warfarin with an INR >8 with no bleeding
Stop warfarin
IV phytomenadione by mouth orally
Repeat dose of vit K if INR still too high after 24hours
Restart when INR <5
A patient on warfarin with an INR of >8 with minor bleeding
Stop warfarin
Give phytomenadione/vit K1 by slow IV injection
Repeat dose of vit K if INR still too high after 24hrs
Restart INR <5
A patient on warfarin with major bleeding
Stop warfarin
Give phytomenadione/ Vit K by slow IV injection and or dried prothrombin complex/ fresh frozen plasma (less effective)
When would you use dried prothrombin complex/frozen plasma in warfarin patients
When a warfarin patient has major bleeding, you add if if IV vitmain K isnt effective alone
Which is more effective fresh plasma or dried plasma
Dried
Warfarin drug interactions
Miconazole, fluconazole, itraconazole
St johns wart
Heavy alcohol
Amiodarone
Aspirin
Bezafibrate
Carbamazepine
Ciprofloxacin
Warfarin and ciprofloxacin interaction
Increases warfarin anticoagulation effect
Amiodarone and warfarin interaction
Increases anticoagulant effect
Aspirin and warfarin interaction
Increased bleeding risk
Carbamazepine and warfarin interaction
Decreases the effects of warfarin
Clotrimozole and warfarin interaction
No interaction
Fluconazole and warfarin interaction
Increases anticoagulant effect
Warfarin and clarithromycin interaction
Increases anticoagulant effect of warfarin
Greeny leafy veg/green tea and warfarin interaction
Affects anticoagulant control
Theres a higher risk of bleeds with warfarin and
Aspirin or clopidogrel
Clopidogrel
A patient is on antiplatelet therapy - aspirin and requires warfarin, what do you do
Withhold aspirin until if possible or only use it short term
Heparin (unfractionated) onset and duration of action
Rapid onset but short duration of action
In high risks of bleeding patients taking warfarin, which is preferred, warfarin or heparin and why
Heparin because it has a short duration of action hence if bleeds occur and you withhold/ stop heparin the effect will be removed quicker
Can heparins be used in pregnancy and why
Yes because they dont cross the placenta
LMWH indications
DVT, PE, MI
Which is preferred, LMWH or standard heparin (unfractionated) and why
LMWH because of lower risks of osteoporosis and heparin induced thrombocytopenia
Monitoring requirements for LMWH
Doesnt require any
Which has a longer duration of action
Heparin
LMWH
LMWH hence can be given OD subcutaneously
What medications are licensed for extended treatment and prophylaxis in VTE patients with solid tumours
How many units/ml
Deltaparin and tinzaparin
20,000units/ml syringe
Are anti platelets given for primary or secondary prevention
Secondary prevention
Examples of antiplatelets
Ticagrelor
Aspirin
Dipyridamole
Clopidogrel
Prasugrel class
Antiplatelet
Cangrelor class
Antiplatelet
Antiplatelet MOA
Glycoprotein IIb/IIIa inhibitors such as tirofiban, eptifibatide, abciximab
Why isnt aspirin used in primary prevention
No benefit in patients with or without diabetes
If a patient is on an antiplatelet and is at a high risk of bleed you can give ….
PPI
dipyridamole dose for secondary prevention of ischaemic stroke and TIA
200mg BD with food
Dipyridamole dispensing information
It should be dispensed in original container- dont split because pack contains desiccant.
Any remaining caps should be discarded after 6 weeks of opening
Discard dipyridamole………… after opening
6 weeks
Aspirin secondary prevention dose
75mg OD
Aspirin secondary prevention in deep vein thrombosis or pulmonary embolism dose
75mg OD or 150mg
Aspirin dose in Suspected TIA
300mg once daily until diagnosis established
Long term management of TIA and ischaemic stroke not associated with AF aspirin dose
75mg OD with or without dipyridamole
Acute ischaemic stroke aspirin dose
300mg daily for 14 days
24hrs after alteplase (thrombolysis) or 48hrs within symptom onset in patients not receiving alteplase
AF following disabling ischaemic stroke aspirin dose
300mg daily for 14 days whilst being considered for anticoagulant treatment
Warfarin dose
Initially 5-10mg (adjusted to INR later) - day 1
Maintenance dose 3-9mg same time each day
Is warfarin preferred in valvular or non valvular AF
Valvular
Warfarin interaction with green tea
Reduces warfarin affect
Does warfarin interact with smoking
Yes
If a person taking warfarin stops smoking, their INR might increase
