Chapter 2: Cardiovascular system Flashcards
Which NOAC has twice daily dosing? Which has once daily dosing?
Twice daily: Apixaban (5mg BD), Dabigatran (150mg BD)
Once daily: Rivaroxiban (20mg OD), Edoxaban (30-60mg OD)
Which NOAC requires loading?
Apixaban 10mg twice daily for 7 days followed by 5mg BD maintenance (loading not required for prophylaxis)
Which DOAC interacts with verapamil and subsequently requires a dose reduction? What other medication has the same interaction?
Dabigatran
Verapamil increases dabigatran levels, so patients also on verapamil need to take a reduced dose of dabigatran (110mg BD as opposed to 150mg BD)
Same with amiodarone- use max dose of 110mg dabigatran with amiodarone
Which one of the NOACs is a DIRECT THROMBIN inhibitor?
Dabigatran is a direct thrombin inhibitor
An INR within ____ units of the target range is generally satisfactory
0.5 units
A target INR of ____ is used for most things! Eg treatment of DVT/PE, AF patients, electrical cardioversion, myocardial infarction…
2.5
Do the NOACS have any food interactions?
No But remember to take Rivaroxiban with food to increase absorption
Which NOAC may be crushed an mixed with apple purée/ put through an NG tube before administration?
Rivaroxaban
Which CCBs need to be avoided in Heart failure?
Verapamil and diltiazem
When should a target INR of 3.5 be used? What is the target for most other conditions?
If the patient has a VTE whilst on treatment with warfarin (with an INR above 2).
Mechanical heart valve
Warfarin’s time to peak effect ranges from 3-5 days, so it is not good if immediate effects are needed. NOACs have a much faster onset to action, what is this? Which is the fastest?
1 - 4 hours
Dabigatran fastest: peak action 0.5-2 hours after oral admin
Edoxaban: 1-2 hours onset of action
Apixaban and rivaroxaban take around 2-4 hours to peak
What is the difference between Phytomenadione and Phenindinone?
Phytomenadione (vit k) is the reversal agent for warfarin overdose
Phenindinone is another oral anticoagulant (coumarin) like warfarin!
What baseline tests do patients need before commencing on a NOAC? Which NOAC is least likely to be chosen with renal impairment ?
Baseline renal function - dose reduction required in renal impairment
Dabigatran has most caution with renal function: it is CI if CrCl is under 30 ml/min
Which NOACs should not be used in severe liver disease?
All
We know that warfarin interacts with a lot of the CYP enzyme inhibitors and inducers, Which NOACs also have a similar problem? Can you think of any interactions?
All
CYP3A4 inhibitors (sickfaces.com) effect these: ketoconazole, itraconazole, Inducers effect these: carbamazepine, rifampicin, phenytoin, St. John’s wort
Which NOAC cannot be put in a compliance aid?
Dabigatran
Which DOAC needs the warning label “swallow whole, do not chew or crush”
Dabigatran
Which is more problematic if a dose is missed, warfarin or the NOACs?
NOACs - shorter half life so if dose is missed there is more time without coagulation If miss a dose of a NOAC
What is the reversal agent for LMWHs?
Protamine sulfate
Name me three LMWHs
Dalteparin Enoxaparin Tinzaparin
When in pregnancy should warfarin be avoided?
First trimester
Crosses the placenta especially in the third trimester
Safe in breast feeding
When used for the prophylaxis of stroke in AF what are the 3 characteristics which are used to identify if a dose reduction is required.
age 80+
body weight 60kg or less
Serum creatinine of 133 or greater
Which NOAC causes the most GI side effects?
Rivaroxaban: constipation, diarrhoea, abdo pain, nausea, vomiting
Also causes: pain in extremities, Pruritis (itching), Rash
What is heparin induced thrombocytopenia and which heparins is it more common with?
Development of very low platelet count
It is an immune mediated reaction that can develop after 5-10 days
More common with UFH than LMWHs
Management: stop the heparin, use something else like Heparinoids