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MHD/Pharm Block 4 > Pharm: Heparin Anticoagulants > Flashcards

Pharm: Heparin Anticoagulants Flashcards

1
Q

Describe where heparin is found naturally within the body

A

Found in mast cell granules with histamine and serotonin

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2
Q

Describe the chemical structure of heparin

A

Strongly acidic mucopolysaccharide with repeating units of sulfated glucuronic acid and sulfated glucosamine

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3
Q

Describe the size of heparin

A

Heterogenous

Molecular weight varies between 2kDa and 40kDa

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4
Q

What is the mechanism of action of heparin?

A

Inhibits action of Xa, IIa, XIIa, Xia (2,10,11,12)

by binding to ATIII and increasing ATIII affinity for these factors

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5
Q

What are the actions of heparin?

A

Plasma clearing
Neutralization of vascular lining
Release of tissue factor pathway inhibitor (TFPI)

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6
Q

What is the route of administration of heparin?

A

IV or subcutaneous

Not absorbed orally or rectally

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7
Q

How is heparin therapy monitored?

A

Heparin therapy is carefully monitored using APTT

Target APTT is 2-2.5x baseline

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8
Q

How is heparin metabolized?

A

25% excreted in urine
Some metabolized in liver by heparinases
Mast cells take up heparin
Endothelium binds heparin

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9
Q

Describe the pharmacokinetics of heparin

A

PK of heparin is dose dependent

Higher doses, longer half life

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10
Q

What are the endogenous modulators of heparin action?

A

ATIII
Heparin cofactor II
Tissue factor pathway inhibitor (TFPI)
Platelet factor 4 (PF4)

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11
Q

What are the side effects of heparin?

A

Hemorrhagic complications
Heparin induced thrombocytopenia
Osteoporosis –> fracture risk
Alopecia (loss of hair)

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12
Q

What are the clinical uses of heparin?

A

Therapeutic, surgical and prophylactic ANTICOAGULATION
Unstable angina
Adjunct therapy with thrombolytic drugs
Thrombotic and ischemic strokes

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13
Q

What is the antagonist of heparin?

A

Protamine: very basic protein derived from fish sperm
Combines with heparin to form stable salt with no anticoagulant activity
1:1 antagonism

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14
Q

Describe the structure of chemically synthesized heparin

A

Composed of pentasaccharide

Mimics the sequence repeats found in natural heparin in order to maintain ATIII interaction

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15
Q

How does the bioavailability of LMW heparin differ from native heparin?

A

LMW heparin has 100% bioavailability unlike native heparin which has ~30% bioavailability

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16
Q

What are the clinical advantages of LMW heparin

A

Better bioavailability, longer duration of action, less bleeding, lesser thrombocytopenia

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17
Q

What are the clinical uses of LMW heparin

A

DVT: Prophylaxis and treatment
Acute coronary syndromes management
Anticoagulation during procedures

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18
Q

What are antithrombin concentrates clinically used for?

A

Congenital antithrombin deficiency

Sepsis and DIC

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19
Q

What is hirudin?

A

A thrombin inhibitor derived from leaches

Used for anticoagulation in thrombocytopenic patients

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20
Q

What is argatroban?

A

A synthetic anti-thrombin agent used as an anticoagulant alternative to heparin for patients with heparin induced thrombocytopenia

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21
Q

What is bivalirudin?

A

A synthetic antithrombin that is a combination of hirudin and a tripeptide
used for anticoagulation during stent placement and angioplasty

22
Q

What is fondaparinux?

A

Pentasaccharide
Complexes with ATIII in order to inhibit factor Xa
Used for management of DVT

23
Q

What is the most common side effect of heparin and related drugs?

A

Bleeding

24
Q

What is the mechanism of action of argatroban, bivalirudin and hirudin?

A

Directly inhibits IIa (thrombin)

25
Q

What is the main oral anticoagulant prescribed in the US?

A

Warfarin

26
Q

What are the clinical uses of warfarin?

A

Prophylaxis for thrombotic disorders

Treatment of established thrombus

27
Q

What class of drugs does warfarin belong to?

A

Vitamin K antagonists (VKAs)

28
Q

What coagulation factors does warfarin act on?

A

II, VII, IX, X

29
Q

Warfarin is an analogue of _________

A

Vitamin K

Warfarin and Vit K have similar chemical structures

30
Q

What is the mechanism of action of warfarin?

A

Inhibit II, VII, IX, X by preventing carboxylation of glutamic acid, thus preventing Ca2+ binding

31
Q

What is the route of administration for warfarin?

A

Oral

32
Q

Is warfarin plasma bound?

A

Yes, 97% bound to albumin

This gives warfarin a long half life

33
Q

How is warfarin metabolized?

A

Liver: hydroxylated in hepatic ER into inactive compound

34
Q

What lab test is used to monitor warfarin therapy?

A

PT is used to monitor warfarin and its effect on the extrinsic pathway

35
Q

How is INR calculated?

A

INR is a normalized PT value

INR = PT_patient / PT_normalcontrol

36
Q

What factors effect the dose of oral anticoagulants?

A

Nutrition, anemia, liver disease, biliary obstruction, drugs

37
Q

What are the main drug-drug mechanisms leading to potentiation of warfarin’s effect?

A 
Causing vit K deficiency (ABX)
Displacing warfarin from albumin
Decreasing clotting factor synthesis
Decreasing metabolism
Antiplatelet aggregating properties
38
Q

What are the main drug-drug mechanisms leading to inhibition of warfarin’s effect?

A

Decreasing absorption of warfarin

Increasing metabolism of warfarin

39
Q

What are the main side effects of warfarin?

A

Bleeding due to hypoprothrombinemia (ecchymoses, purpura, hematuria, hemorrhage)

40
Q

Is warfarin safe to give to pregnant women?

A

No. Warfarin passes the placental barrier and can cause fetal malformation

41
Q

How does warfarin cause necrosis?

A

Impaired functionality of protein C due to inhibition of gamma carboxylation of glutamic acid

42
Q

What is the treatment of warfarin overdose?

A
  • Replacement of factors II, VII, IX, X via whole fresh blood infusion or frozen plasma
  • Recombinant factor VIIa
  • Vitamin K
43
Q

What are the therapeutic uses of vitamin K?

A
  • Antidote for drug-induced hypoprothrombinemia
  • Intestinal disorders and surgery
  • Hypoprothrombinemias in newborns
44
Q

What are the anti-Xa drugs?

A

Apixaban
Edoxaban
Rivaroxaban

45
Q

What are the interactions with anti-Xa drugs?

A

Anti-Xa drugs are potent CYP3A4 inhibitors

46
Q

What is the target of Dabigatran?

A

Factor IIa (thrombin)

47
Q

Do the new oral anticoagulants require coagulation monitoring?

A

No.

48
Q

What is a contraindication for dabigatran?

A

Renal failure

Dabigatran is 100% cleared by the kidney

49
Q

What class of drugs does dabigatran interact with?

A

Proton pump inhibitors

50
Q

What are the indications for the anti-Xa drugs?

A

Stroke prevention in AFib patients

Prophylaxis of DVT

51
Q

What is the indication for dabigatran?

A

Stroke prevention in AFib patients

MHD/Pharm Block 4 (25 decks)

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