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Pharm > Antithrombotics > Flashcards

Antithrombotics Flashcards

1
Q

Explain the formation of a blood clot

A

2 coagulation pathways: Intrinsic pathway from contact with damaged surface, and extrinsic pathway from trauma

  • Come together at the activation of FX to a common pathway of fibrin formation.

-Factor Xa converts prothrombin (FII) to thrombin (FIIa) with the help of calcium and phospholipids from activated platelet membrane and factor Va.

  • Thrombin (FIIa) activates factor XIII to XIIIa to form a “net” that catches RBCs -> forming a clot
  • Fibrin retracts to form a thrombus.
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2
Q

What are the three antithrombotic drugs classifications?

A

Antiplatelet agents
Anticoagulants
Thrombolytics

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3
Q

What are the examples of antiplatelets agents and what do they do?

A

-ASA (aspirin)

They inhibit platelet aggregation.

Used for acute coronary syndromes and MI.

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4
Q

What are the examples of anticoagulants and what do they do?

A

-Direct acting: Heparin, factor Xa inhibitors, DTI (direct thrombin inhibitors)
-Indirect Acting: Warfarin

Used for Stroke, PE and DVT

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5
Q

What are examples of thrombolytics and what do they do?

A

They lyse existing clots in patients with stroke, MI and PE.

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6
Q

What are the three kinds of laboratory monitoring used for these drugs?

A

Bleeding time
Activated Partial thromboplastin time PTT or aPTT
Prothrombin time PT now called INR

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7
Q

What does bleeding time measure and which antithrombotic medications affects it?

A

-Measures ability of platelets to initiate clotting
Increased by anti-platelet drugs.

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8
Q

What is PTT or aPTT and which medication affect it?

A

Activated partial thromboplastin time
-Measures ability of intrinsic pathway to form thrombus
Increased by DIRECT ACTING anticoagulants to 1.5-2.5 the normal pace

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9
Q

What is PT and which medications affect it?

A

Prothrombin time
-Measure the ability of extrinsic pathway to form a thrombus
Increased by INDIRECT ACTING anticoagulant.

PT is now reported as INR (international normalized ratio)

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10
Q

What are the three “methods” antiplatelets block aggregation targets?

A

COX-I inhibitor
ADP or P2Y12 Receptor antagonists
GP2b/3A inhibitors

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11
Q

What does a COX-I Inhibitor do?

A

Platelets hace an enzyme called cyclooxygenase (COX-I) that synthesized to create thromboxane A2 (TA2) that promotes platelet aggregation.

COXI Inhibitors blocks the enzyme.
ASPIRIN

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12
Q

What doe P2Y12 Receptor antagonists do?

A

“Stimulated” platelets release ADP which interacts with P2Y12 receptors on the platelet membrane to produce aggregation.

P2Y12 receptor antagonists block the receptor
- Clopidogrel bisulfate
- Ticlopidine hydrochloride
- Prasugrel hydrochloride
- Ticagrelor

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13
Q

What do the GP 2b/3a inhibitors do?

A

After activation, platelets express the IIb/IIIa glycoprotein receptor, which mediates cross link between fibrinogen molecules and platelets.

GP2b/3a are competitive antagonists, that block the formation.

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14
Q

After you take a PO dose, apsirin acts as a _ converting into _.

A

Prodrug, salicylates

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15
Q

Does salicylates bind reversible or irreversibly to COXI?

A

Irreversibly- the affected platelets cannot synthesize new COXI either, so no new TA2 either.

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16
Q

What is aspirin used for prophylactically?

A

To lower the incidence of MI, transient ischemic attacks, ischemic stroke, re-occlusion of coronary re-vascularization procedures and stent implantation.

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17
Q

What should you not give with Aspirin? Why not?

A

NSAIDs because they also block COXI and they become competitive antagonists for ASA

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18
Q

What is a symptom sensitive patients might get from aspirin use?

A

Tinnitus

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19
Q

Aspirin is?

A

An anti-platelet drug

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20
Q

What two anti-platelet medications put together inhibit platelet aggregation even more than ASA alone?

A

Clopidogrel and low dose ASA

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21
Q

Name ADP/P2Y12 Receptor Antagonists

A

Clopidogrel
Prasugrel
Ticagrelor
Cangrelor
Ticlopidine

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22
Q

What is the difference between Clopidogrel, Prasugrel vs. Ticagrelor, Cangrelor? What do they have in common?

A

All 4 inhibit binding of ADP to P2Y12 receptors on platelet cell membrane, and inhibit ADP-dependent platelet activation.

Clop + Pras = irreversible antagonists
Tica + Cang= Reversible antagonists

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23
Q

Which ADP/P2Y12 receptor antagonist/s are of limited use nowadays? Why?

A

Ticlopidine- neutropenia toxicity

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24
Q

What are ADP/P2Y12 receptor antagonists used for?

A

They treat and prevent acute coronary syndrome, MI, strokes, peripheral vascular disease, and prevent re-occlusion during/after PCT

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25
Q

Name the CYP used to metabolize Clopidogrel

A

CYP2C19

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26
Q

What drug interaction would you suspect to interfere with clopidogrel?

A

Protein pump inhibitors or any drug that uses CYP2C19

27
Q

What makes Prasugrel possibly better than clopidogrel?

A

Has a shorter 1/2 life so it has a rapid and consistent effect
Esterase metabolism-> abundantly available in the body

28
Q

Which ADP/P2Y12 receptor antagonist is independent of CYP?

A

Cangrelor

29
Q

What does heparin do?

A

Anti-thrombin III (ATIII) is a weak inhibitor of activated clotting factors (thrombin, Xa).

Heparin increases the interaction between circulating ATIII to Xa and to IIa for immediate and irreversible inhibition of Xa-mediated conversion of II to IIa.

30
Q

What are the two kinds of heparin?

A

Unfractionated
LMWH

31
Q

Name the three LMWH

A

Enoxaparin
dalteparin
tinzaparin

32
Q

What is LMWH different from heparin?

A

Fractionated from heparin (BIG MOLECULE) to lower affinity to thrombin.

Inhibits Xa but less inhibitory effect towards thrombin (F II)

33
Q

What is fondaparinux?

A

It is a drug that is similar to LMWH, given subcutaneously.
It inhibits Xa but not FIIa.

34
Q

What is the difference in administrating LMWH vs heparin?

A

LMWH is subcutanous only, and heparin can be given through IV and subcutaneously

35
Q

What’s the difference in half life between LMWH vs heparin?

A

LMWH= 3-5 hrs
Heparin= 1-2 hrs

36
Q

How do the ADRs of LMWH vs heparin differ?

A

LMWH has a lower incidence of bleeding, thrombocytopenia, skin necrosis in comparison to heparin.

37
Q

Which can be given in pregnancy? LMWH vs heparin?

A

Both, only LMWH is better for preganancy.

38
Q

What is the antidote for LMWH and heparin?

A

Protamine

39
Q

LMWH has a _ reversal from protamine

A

Partial

40
Q

What is heparin induced thrombocytopenia?

A

Heparin binds to platelet F4 and antibodies against the F4-complex bind on the platelet and aggregate.

DC all heparin and start using DTI, Xa inhibitor or Warfarin

41
Q

What is the name of the indirect-acting anticoagulant?

A

Warfarin

42
Q

What are the inactive clotting factors that are dependent on vitamin K for activation?

A

II, VII, IX, X

43
Q

What enzyme is used to activate II, VII, IX, X?

A

Vitamin K reductase

44
Q

What drug inhibits vitamin k reductase?

A

Warfarin

45
Q

What 2 facts about warfarin makes it significantly metabolized by the liver?

A

99% bound to proteins
CYP mediated

46
Q

Which CYPs are used for warfarin?

A

CYP2C9 for S-warfarin
CYP1A2, CYP2C19, CYP3A4 R-warfarin

47
Q

What drugs increase the effects of Warfarin- why?

A

Fluconazole, amiodarone, bactrim, metronidazole.

They use the same CYPs.

NSAIDS and ASA- they work on the platelet, too.

48
Q

What drugs lower the effects of warfarin?

A

Carbamazepine
Rifampin
phenytoin (vitamin K) duhh

49
Q

What foods have a high vitamin K?

A

Kale, collard greens, spinach, turnip greens, brussel sprouts, broccoli

50
Q

Genetic variations in which two enzymes can change the sensitivity and metabolism of warfarin?

A

VKORCI
CYP2C9

51
Q

What are the ADRs of warfarin?

A

Increased bruising, bleeding teratogens.

52
Q

What 2 ways can the ADRs of warfarin be reversed?

A

Phytonadione (vitamin K)
Fresh frozen plasma with the four factors

53
Q

What is warfarin used for?

A

Prophylaxis and treatment of thromboembolic disorders and embolic complications from atrial fibrillation or valve replacement.

54
Q

Due to warfarin’s narrow TI, what should the INR be between?

A

2-3

55
Q

Name the direct oral Xa inhibitors

A

Rivaroxaban,
Edoxaban
Betrixaban
Apixaban,

56
Q

Name the DTI- direct thrombin inhibitor

A

Dabigatran

57
Q

What are the benefits of direct oral Xa inhibitors?

A

Smaller DDI, food effects, better predictability, no monitoring required, no effect on PT.

58
Q

What is the reversal agent of DTI?

A

Ida-rucizu-mab

59
Q

What is the reversal agent for the direct Xa inhibitors?

A

Andexanet

60
Q

What are the names of 3 thrombolytics t-PA?

A

Alteplase
Reteplase
Tenecteplase

61
Q

What is a major ADR involved with thrombolytics?

A

Hemorrhage

62
Q

What reverses thrombolytics?

A

A2-antiplasmin, aminocaproic acid, tranexamic acid, whole blood, packed RBC, fresh frozen plasma.

63
Q

How do thrombolytics (t-PA) work?

A

After completion of normal vascular repair, tissue plasminogen activator t-PA released from vascular endothelial cells. Cleaves plasminogen to plasmin which degrades fibrin net.
Lyses fibrin strands w/i clot.

Pharm (11 decks)

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