Anticoagulant Flashcards
list 2 drug that reduce rivaroxaban level
- p-gp inducer
- CYP3A4 inducer
what is the pharmacokinetic of the anticoagulant action of oral warfarin
onset: 24-72hrs
peak: 5-7 days
duration: 2-5 days (due to the long half life of some of the factor eg II T1/2 50hrs)
where is warfarin metabolise + which enzyme
in the liver, primary by CYP2C9
list 3 a/e of heparin/LMWH
- bleeding
- thrombocytopenia (lesser risk w LMWH)
- increase risk of epidural/spinal haematoma & paralysis in pt receiving epidural/spinal anaesthesia or spinal puncture
what is the pharmacokinetic for dabigatran
onset: ~1hr
peak: 3h
duration: 3-5 days
list examples of significant drug-drug interactions with warfarin
- paracetamol >2 weeks at high dose >2g/day (increase risk of bleeding)
- allopurinol, NSAIDS, salicylates, PPI, metronidazole (increase risk of bleeding)
- barbiturates, corticosteroids, spironolactone, thiazide diuretic (reduce drug effect)
list 1 adverse effect of rivaroxaban
bleeding
list example of drug-drug interaction with dabigatran that increase the risk of bleeding
- antiplatelet
- anticoagulants
- fibrinolytic
- NSAIDS
- ketoconazole
what is the pharmacokinetic of heparin
onset: 5-25min
duration: 4hr
list 1 drug-drug interaction that increase the risk of bleeding with heparin/LMWH
SSRI (selective serotonin reuptake inhibitor)
what is the 4 contraindication over the use of heparin/LMWH
- hypersensitivity to pork product
- active bleeding
- thrombocytopenia
- antiplatelet antibodies
list example of drug-drug interaction with rivaroxaban that increase the risk of bleeding
- antiplatelets
- anticoagulants
- NSAIDS
- p-gp inhibitor
- CYP3A4 inhibitor
name a reversal agent for rivaroxaban
andexanet alfa
does dabigatran have a short or long bioavailability, what advice should be given to patient
short, instruct pt to swallow the medication whole (enteric coated)
a 62 y/o man admitted with DVT is stabilised and restarted on a lower dose of LMWH overlapped with warfarin in preparation of discharge. why is warfarin more appropriate for outpatient therapy
a) warfarin can easily be administered orally
b) warfarin is a safe drug with no drug-drug or drug-food interactions
c) the risk of bleeding with warfarin is less than any other anticoagulant
A
list the 3 adverse effects of warfarin
- haemorrhage/bleeding
- hepatitis (greater risk in >60 y/o, male, warfarin <1 month)
- cutaneous necrosis due to reduce blood supply to adipose tissue, typically 3-5 days after treatment initiated
what does anticoagulant block in haemostasis (2)
- block the activation of clotting factor
- block the activation of fibrin polymerization
list examples of significant drug-food interactions with warfarin
- traditional herb eg. gingko, ginseng, cranberry juice (increase risk of bleeding)
- vitamin k food eg. green tea, leafy green veg (reduce drug effect)
list 5 contraindications over the use of warfarin
- active/risk of bleeding
- severe/malignant HTN
- severe renal/hepatic disease
- subacute bacterial endocarditis, pericarditis, pericardial effusion
- pregnancy (teratogen cause severe birth defects in CNS & bones, drug also cause hemorrhagic disorder in fetus)
what is the antidote for heparin/LMWH
IV protamine sulfate
incomplete reversal of LMWH
what class of drugs inhibits secondary haemostasis
anticoagulant
list 5 caution over the use of warfarin
- diverticulitis, colitis
- mild-mod HTN
- mild-mod renal/hepatic disease
- breast feeding women
- drainage tube in any orifice
what is the difference between heparin & LMWH in terms of inactivating clotting factors
LMWH are more selective towards factor Xa & to a lesser extend factor IIa
a 62 y/o man is admitted to the ED & diagnosed to have DVT in a lower limb, why was he not administered warfarin immediately
a) the risk of bleeding is too great before the patient is stabilised
b) heparins are more potent as they directly inhibit activation of thrombin
c) warfarin is only antiplatelet not anticoagulant
d) the onset of clinical action of warfarin is too slow
D
list 2 a/e of dabigatran
- bleeding
- GI disturbance eg. dyspepsia, abdominal discomfort
what is the pharmacokinetic of LMWH
onset: 5-25min
duration: 20hr
what is the 3 advantage of LMWH over heparin
- longer half life
- longer bioavailability
- lesser risk of thrombocytopenia
list examples of drug-food interaction that increase the risk of bleeding with heparin/LMWH
gingko, ginseng, ginger, garlic
name 4 pharmacological classes of oral anticoagulant drugs
- vitamin k antagonist
- direct oral anticoagulants (DOAC): factor IIa inhibitor
- direct oral anticoagulants (DOAC): factor Xa inhibitor
- heparin/LMWH
what is the drug name of the inactive form of dabigatran
dabigatran etexilate
what is the pharmacokinetic for rivaroxaban
peak: 2.5-4hr
duration: 1-2 days
list 3 caution over the use of heparin/LMWH
- risk of bleeding
- elderly
- pt w renal insufficiency (for LMWH)
a patient is discharged with dual therapy consisting of LMWH overlapping with oral warfarin. what commonly available OTC drug that can increase the risk of bleeding with warfarin must the patient avoid?
a) paracetamol
b) antihistamines
c) aspirin
d) vitamin supplements
C
name a reversal agent for dabigatran
idarucizumab
what is the MOA of heparin/LMWH (2)
- it potentiate the action of antithrombin III to inactivate thrombin (IIa)
- heparin-ATIII complex also inactivate other factors: IXa, Xa, XIa, XIIa
name a drug that can be used to reverse the anticoagulation action of warfarin
vitamin k
what is the 2 route for heparin/LMWH
SC/IV
list 1 drug that reduce dabigatran level
rifampin
a 62 y/o man admitted with DVT and administered LWMH develops bleeding. which of the following is the most appropriate cause of action?
a) immediately discontinue LMWH & replace with warfarin
b) immediately discontinue LMWH & administer protamine sulphate
c) continue the LMWH & administer idarucizumab
d) switch to dabigatran
B
list one drug example of LMWH
enoxaparin
which coagulation factors does oral warfarin inhibit
II, VII, IX, X
what is the MOA of warfarin
it inhibit the vitamin k reductase enzyme, preventing the reactivation of oxidised vitamin k
