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CPT > 11. Anticoagulants > Flashcards

11. Anticoagulants Flashcards

1
Q

What do anticoagulant drugs do?

A

Prevent thrombus formation and thrombus growing

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2
Q

What is an important cofactor in many of the coagulation cascade steps?

A

Calcium

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3
Q

What is the role of heparin?

A

Inhibit coagulation in vitro and in vivo- enhance antithrombin III activity

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4
Q

How is unfractionated heparin given?

A

IV bolus and infusion

SC for prophylaxis with low bioavailability

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5
Q

What is the action of unfractionated heparin?

A

Binding to antithrombin III causing conformational change and increased activity of ATIII
To catalyse inhibition of thrombin (IIa), heparin needs to simultaneously bind ATIII and IIa
Xa inhibition only needs ATIII binding

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6
Q

Name some low molecular weight heparins (LMWH)

A

Dalteparin

Enoxaparin

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7
Q

How are LMWH administered?

A

Almost always SC

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8
Q

What is the action of LMWH?

A

Inhibition of Xa specifically - by enhancing activity of ATIII

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9
Q

What are the indications for heparin?

A

Prevention of venous thromboembolism, perioperative prophylaxis with LMWH
During pregnancy used - monitored with caution
DVT and PE - initial treatment, long term in some patients
Acute coronary syndromes

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10
Q

What are the ADR of heparins?

A

Bruising and bleeding - intracranial, at site of infection, GI, epistaxis
Heparin induced thrombocytopenia
Hyperkalaemia - inhibition of aldosterone secretion
Osteoporosis

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11
Q

What are the contraindications for heparins?

A

Clotting disorders, renal impairment

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12
Q

What are the DDI for heparins?

A

Other anti thrombotic drugs

ACEi/ARB and spironolactone

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13
Q

Name a reversal for heparin

A

Protamine sulphate - dissociates heparin from ATIII, irreversible binding

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14
Q

Name a vitamin K antagonist

A

Warfarin

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15
Q

What is the action of warfarin?

A

Inhibit activation of vitamin K dependent clotting factors

Inhibits conversion of vitamin K to active reduced form - competitive inhibition of VKOR

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16
Q

Which clotting factors require vitamin K as cofactor for activation?

A

II, VII, IX, X

17
Q

What are the indications for warfarin?

A 
Venous thromboembolism
PE
DDVT and secondary prevention
Superficial vein thrombosis 
Atrial fibrillation with high risk of stroke
Heart valve replacement
Longer term anti coagulation
18
Q

What are the contraindications for warfarin?

A

Avoided at least in 1st and 3rd trimesters of pregnancy

Hepatic disease

19
Q

What is the response of warfarin affected by?

A

CYP2C9 and others
Vitamin K intake
Alcohol

20
Q

What are the ADR of warfarin?

A

Bleeding

Epistaxis and spontaneous retroperitoneal bleeding

21
Q

What are the DDI for warfarin?

A

Inhibition of hepatic metabolism esp. CYP2C9 - amiodarone, clopidogrel, intoxicating dose of alcohol
Cephalosporin antibiotics - reduce vit K
NSAIDs, drugs that decrease GI absorption of vit K
Barbiturates, phenytoin, rifampicin, St Johns wort - acceleration of warfarin metabolism

22
Q

What must be monitored in patients taking warfarin?

A

INR - clotting time against a standard
DVT, PE, AF - INR 2.5
Recurrent DVT or PE - INR 3-3.5

23
Q

Name some direct acting oral anticoagulants (DOAC)

A

Apixaban (Xa)
Edoxaban (Xa)
Rivaroxaban (Xa)
Dabigatran (IIa)

24
Q

What is the action of direct Xa DOACs?

A

Inhibit both free Xa and that bound with ATIII, do not directly effect thrombin (IIa)

25
Q

What is the action of direct IIa DOACs?

A

Selective direct competitive thrombin inhibitor, both circulating and thrombus bound IIa

26
Q

What are the ADR of DOACs?

A

Bleeding

27
Q

What are the contraindications of DOACs?

A

Dabigatran contraindicated in low creatinine clearance, others are at ver low creatinine clearance
Avoid in pregnancy and breastfeeding

28
Q

What are the DDI of DOACs?

A

Affected by CYP inhibitors and inducers
Carbamazepine, phenytoin, barbiturates
Macrolides

CPT (30 decks)

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