Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PR3154 > IC3 Anticoagulants > Flashcards

IC3 Anticoagulants Flashcards

1
Q

Which step of hemostasis do Anticoagulants block?

A
  • Secondary hemostasis
  • Block activation of fibrin polymerization by preventing conversion of fibrinogen to fibrin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

List & classify the Anticoagulants according to their route of administration

A

Oral
Warfarin
Dabigatran
Rivaroxaban

Parenteral
Heparin
LMWHs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which oral Anticoagulants are antagonists of Vitamin K & which are not?

A

Vitamin K Antagonist
Warfarin

Non-Vitamin K Antagonist
Dabigatran
Rivaroxaban

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the MOA of Warfarin?

A
  • Active Vitamin K = reduced form
  • Inactive Vitamin K = oxidised form
  • Active Vitamin K is oxidised to inactive Vitamin K in a step that is coupled to the carboxylation of glutamic acid residues (on coagulation factors II, VII, IX & X)
  • Carboxylation activates the factors II, VII, IX & X
  • Warfarin inhibits Vitamin K reductase, the enzyme that reactivates the oxidized Vitamin K → Prevents activation of clotting factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the reversal agent for Warfarin?

A

Vitamin K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the onset, time to peak plasma concentration & duration of action of Warfarin?

A

Onset
24 to 72h for oral, effects kick in when endogenous reserves of active vitamin K are depleted

Time to peak, plasma
2 to 8h for oral

Duration of action
2 to 5 days

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How long is needed before full therapeutic effect can be achieved for Warfarin? Suggest why

A
  • 5 to 7 days
  • As some of the coagulation factors have a long half-life
    e.g. Factor II (prothrombin) has T1/2 = 50 h
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How well absorbed is Warfarin & how is it excreted?

A

Absorption
Rapid & complete oral absorption

Excretion
Urine & faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is Warfarin metabolised & what is its half life elimination?

A
  • Metabolised by liver, primarily via CYP2C9
  • Half-life elimination is 20-60 hours, highly variable among individuals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why does Warfarin have a variable response?

A
  • Mostly due to genetic polymorphisms in 2 genes
    CYP2C9 & Vit K reductase complex, subunit 1 or VKORC1
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the 2 main parameters used to monitor & titrate Warfarin dose?

A
  • International normalized ratio (INR)
  • Prothrombin time (PT)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a common adverse effect of Warfarin?

A

Haemorrhage / bleeding 🩸
Signs include blood in stools or urine, melaena (sticky, tar-like stools), excessive bruising, petechiae, persistent oozing from superficial injuries, excessive menstrual bleeding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the rare adverse effects of Warfarin? State the risk factors if any

A

Hepatitis
Greatest risk if >60 y/o, male, on warfarin < 1 month

Cutaneous necrosis & infarction of breast, buttocks and extremities
Likely due to ↓ blood supply to adipose tissue
Typically occurs 3 to 5 days after initiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the contraindications of Warfarin?

A
  • Hypersensitivity to drug
  • Bleeding associated: Active bleeding, risk of pathologic bleeding, after recent major surgery
  • Severe or malignant hypertension
  • Severe renal or hepatic disease
  • Subacute bacterial endocarditis, pericarditis, or pericardial effusion
  • Pregnancy (teratogenic: severe defects in bone & CNS, can cause haemorrhagic disorder in fetus)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In whom should cautions be taken for Warfarin?

A
  • Breast-feeding women
  • Diverticulitis, colitis
  • Mild or moderate hypertension
  • Mild or moderate renal / hepatic disease
  • Drainage tubes in any orifice
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the drugs that may increase bleeding risks when used concomitantly with Warfarin?

A
  • Paracetamol (warn patients! can get OTC easily)
    when used long term (>2 weeks) at high doses (> 2g/day)
  • CYP2C9 inhibitors (allopurinol, NSAIDs, salicylates, PPI, metronidazole)
  • Other antiplatelets or anticoagulants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the traditional medicines/herbs/supplements/food that may increase bleeding risks when used concomitantly with Warfarin?

A
  • Gingko 🍁
  • Ginseng
  • Reishi mushrooms 🍄
  • Cranberry juice
18
Q

What drugs may reduce the efficacy of Warfarin when used concomitantly?

A

CYP2C9 inducers
* Barbiturates
* Corticosteroids
* Spironolactone, thiazide (diuretics)

19
Q

What are the traditional medicines/herbs/supplements/food that may reduce the efficacy of Warfarin when used concomitantly?

A
  • Vitamin K containing supplements
  • Vitamin K-rich foods (mustard greens, spinach)
    Ask patients to avoid excess vitamin K intake
  • Green tea
20
Q

What should we monitor for drug-drug or drug-food interactions that may reduce efficacy of Warfarin?

A

Regular INR monitoring to ensure appropriate anticoagulant control

21
Q

Which DOAC is a prodrug?

A

Dabigatran etexilate
rapidly converted to dabigatran

22
Q

What is the difference between the target(s) of Dabigatran vs Rivaroxaban?

A
  • Dabigatran & its acyl glucuronide metabolites are competitive reversible non-peptide antagonists of thrombin (factor IIa) while
  • Rivaroxaban is a competitive reversible antagonist of activated factor X (Xa)
23
Q

Which drug is Idarucizumab used as a reversal agent? Explain what it is & when it is indicated

A
  • Dabigatran
  • Is a humanized mAb fragment that binds Dabigatran & its acyl glucuronide metabolites with higher affinity than Dabigatran to thrombin
  • Indicated for
    1. Emergency surgery or urgent procedures
    2. Life-threatening or uncontrolled bleeding
24
Q

Which drug is 🥨 Andexanet alfa used as a reversal agent? Explain what it is

A
  • Rivaroxaban or other -xabans
  • Off-label for LMWHs
  • Is a recombinant modified human factor Xa decoy protein
25
Q

What are the advantages of DOACs over Warfarin?

A
  • Less drug, food interactions
  • Less interindividual variability
    But DOACs are more expensive
26
Q

Does Dabigatran etexilate or Rivaroxaban take a shorter time for reversal?

A
  • Rivaroxaban
  • Takes 1-2 days as half life is shorter, at 5 to 9h
  • vs Dabigatran etexilate whose reversal takes 3-5 days as half life is longer, at 12 to 17h
27
Q

Compare the adverse effects of Dabigatran etexilate & Rivaroxaban

A
  • Both may cause bleeding
  • Dabigatran etexilate may also cause GI symptoms
28
Q

Does Dabigatran etexilate or Rivaroxaban have better bioavailability?

A
  • Rivaroxaban (80 to 100%)
  • Dabigatran etexilate (3 to 7%…so administered as enteric coated formulation)
29
Q

Compare the drugs that increase bleeding risks of Dabigatran etexilate & Rivaroxaban

A

Dabigatran etexilate
Antiplatelets, anticoagulants, NSAIDs, fibrinolytics & ketoconazole

Rivaroxaban
Antiplatelets, anticoagulants, NSAIDs, P-gp & CYP3A4 inhibitors

30
Q

Compare the respective drugs that reduce the levels of Dabigatran etexilate & Rivaroxaban

A

Dabigatran etexilate
RifamPIn

Rivaroxaban
P-gp & CYP3A4 inducers

31
Q

What is the MOA of Heparin & LMWHs?

A
  • Potentiate the action of antithrombin III (AT III), thereby inactivating thrombin
  • Thrombin is needed for conversion of fibrinogen to fibrin
  • Without fibrin, clot formation is impeded
  • Active heparin molecules bind tightly to AT III → cause a conformational change which exposes AT III’s active site for more rapid interaction with proteases → accelerate inactivation of coagulation factors
32
Q

What are the factors inactivated by Heparin vs LMWHs?

A

Heparin
🥨 Heparin-AT III complex inactivates thrombin (Factor IIa), IXa, 🥨 Xa, XIa & XIIa

LMWHs e.g. enoxaparin
🥨 Factor Xa & to a lesser extent, IIa

33
Q

Which parenteral anticoagulant is good at blocking surface contact triggered coagulation?

A
  • Heparins (not LMWHs)
  • Also used in tubes for blood samples
34
Q

What are the features of LMWHs that make them favourable over Heparin?

A
  1. Longer half-life (4h vs 1h)
  2. Higher bioavailability (86 to 98% vs 30%)
  3. Less need for INR monitoring as response is more consistent
  4. Lower risk of heparin-induced thrombocytopenia
35
Q

Parenteral anticoagulants are administered _______

A

IV, subcutaneously

36
Q

How is LMWHs vs Heparin excreted?

A

LMWHs are excreted renally but Heparins are via nonrenal mechanisms

37
Q

What are the adverse effects of parenteral anticoagulants?

A

1. Bleeding
(in 1-5 % of patients treated with IV heparin)
Anticoagulant effect disappears within hours of discontinuation

2. ↑ Risk of epidural or spinal haematoma & paralysis
in patients receiving epidural, spinal anaesthesia or spinal puncture

3. Heparin-induced thrombocytopenia
Binds to platelet factor 4 (PF4) on activated platelet surface, triggering formation of IgG antibody against the heparin-PF4 complex
Even after discontinuation, antibodies sometimes continue to attack platelets
(Lower risk with LMWHs)

38
Q

How can effects of parenteral anticoagulants be reversed?

A
  • IV infusion of 🥨 Protamine sulfate
  • Mainly for heparin, incomplete reversal if used for LMWHs
  • Is a highly basic peptide that binds stably to negatively charged heparin → neutralise anticoagulant properties of heparin
39
Q

Are parenteral anticoagulants safe for use in pregnancy?

A
  • Both Heparin & LMWH do not cross the placenta (unlike Warfarin)
  • Not been a/w fetal malformations
40
Q

What are the contraindications for parenteral anticoagulants?

A
  • Hypersensitive to heparins or pork products (those hypersensitive to pork showed cross reactivity to heparins)
  • Active major bleeding
  • Thrombocytopenia or antiplatelet antibodies
41
Q

In whom should caution be exercised for parenteral anticoagulants?

A
  • Elderly patients
  • Risk of bleeding
    Including patients with prosthetic heart valves, major surgery, regional or lumbar block anaesthesia, blood dyscrasias, recent childbirth, pericarditis or pericardial effusion & (LMWHs) renal insufficiency
42
Q

What are the drug/food/herb interactions with parenteral anticoagulants?

A

All ↑ risk of bleeding
Drugs
Antiplatelets, anticoagulants, fibrinolytics, NSAIDs, SSRIs

Herbs/foods
Chamomile, fenugreek, garlic, ginger, ginkgo & ginseng

PR3154 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions