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Pharm OTL > Blood Thinners > Flashcards

Blood Thinners Flashcards

1
Q

Whats anti-coagulants are prescribed to pts after an MI?

A

Aspirin - forever

Clopidigrel - 12mths

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2
Q

What is the MoA of the cyclo-oxygenase inhibitor aspirin?

A

Inhibits COX-1 to stop the formation of thromboxane A2 from arachadonic acid.

Therefore inhibits plt aggregation irreversibly for the lifespan of the plt (7-10 days).

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3
Q

State two indications for aspirin

A
  • Secondary prevention of stroke and TIA
  • Secondary prevention of ACS
  • Prevention of an MI in stable angina or peripheral vascular disease
  • Post PPCI and stent
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4
Q

What is the non-analgesic dose of aspirin?

A

75mgs

700mgs for analgesia

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5
Q

Name an ADP/P2Y12 receptor antagonist

A

Clopidigrel

Prasugrel

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6
Q

What is the MoA of ADP receptor antagonists?

A

Irreversibly stops ADP from activating plts via the P2Y12 receptor.

This prevents the activation of GPIIb/IIIa receptors by calcium.

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7
Q

Clopidigrel has a slow onset of action. How can this be overcome?

A

Loading dose

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8
Q

Name a glycoprotein IIb/IIIa inhibtor

A

Abciximab

Tirofiban

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9
Q

What is the MoA of GPIIb/IIIa inhibitors?

A

Blocks the receptors, to prevent the binding of fibrinogen.

Abciximab binds irreversibly, and has >80% reduction in aggregation.

Tirofiban binds reversibly.

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10
Q

State a side effect of GPIIb/IIIa inhibitors

A

Thrombocytopenia

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11
Q

Name a phosphodiesterase inhibitor

A

Dipyridamole

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12
Q

What is the MoA of phosphodiesterase inhibitors?

A

Inhibits phosphodiesterase to prevent the breakdown of cAMP and cGMP. This keeps intracellular calcium low to prevent plt activation.

Inhibits cellular uptake of adenosine, leading to more adenosine in the plasma. This inhibs TXA2 receptors to inhibit activation.

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13
Q

State two indications for dipyridamole

A
  • Secondary prevention of stroke of TIA +/- aspirin.

- Adjuct to other anti-coagulants in pts with prosthetic heart valves.

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14
Q

Name four antiplatelets

A

Aspirin
Clopidigrel
Abiximab
Dipyridamole

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15
Q

Name a fibrinolytic

A

Streptokinase
Alteplase
Tenecteplase

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16
Q

What is the MoA of fibrinolytics?

A

Activates plasminogen

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17
Q

Why can streptokinase be given acutely for coronary artery occlusion, but can’t be given repeatedly?

A

Antigenic - immune system will mount response

18
Q

What is the MoA of warfarin?

A

Inhibs the reduction of vitamin K to it active form.

Therefore vitK can’t be used to make the clotting factors II (prothrombin), VII, IX and X.

19
Q

Why does warfarin take a few days to take effect?

A

Circulating clotting factors are still active.

Takes a few days for them to be cleared.

Therefore need heparin cover for the first few days if anticoagulation is needed immediately.

20
Q

Warfain is a racemic mixture. What is this?

A

Has equal amounts of left and right handed enantiomers

21
Q

What is the half-life of warfarin?

A

36-48hrs

22
Q

State three indications of warfarin

A

DVT and PE prophylaxis and treatment
AF with high risk of stroke
Protein C and S deficiency
Following a major surgery with long stasis e.g. orthopaedic

23
Q

State three effects of drug-drug interactions that increase the INR reading (increased risk of bleeding) and give three example drugs

A
  • Inhibition of CYP2C9 e.g. amiodarone, clopidigrel, binge alcohol, metronidazole
  • Inhibition of platelet function e.g. aspirin
  • Reducing vitK production by eliminating gut bacteria e.g. cephlosporin antibiotics
  • Reducing vitK absorption from the gut e.g. NSAIDs
  • Displacement from albumin by other drugs e.g. sodium valproate
24
Q

Why should pregnant women avoid warfarin?

A

Crosses the placenta.

In the first trimester it’s teratogenic.

In the third trimester can cause brain haemorrhage.

25
Q

State an effect of drug-drug interaction that decreases the INR (increased risk of clotting) and give three example drugs

A

Induction of the metabolic pathway e.g. carbamazepine, oral contraceptive, St John’s Wort, rifampicin, azathioprine

26
Q

A target INR of 2.5 is recommended for which three conditions?

A

DVT prophylaxis
PE prophylaxis
AF

27
Q

A target INR of 3.5 is recommended for which three conditions?

A

Recurrent DVT when pt is already on anticoag

Recurrent PE when pt is already on anticoag

Mechanical prosthetic valve

28
Q

What are the similarities and differences between the MoA of unfractionated heparin, and low molecular weight heparin?

A

Both bind to antithrombin III

Both catalyse the inhibition of factor Xa

Only UFH catalyses the inhibition of thrombin

29
Q

What is the difference in dose response between UFH and LMWH?

A

UFH is non-linear and unpredictable. Bioavailability is variable, and UFH can bind to different things e/g/ endothelium and macrophages

LMWH is linear and predictable. Bioavailability is constant 90%

30
Q

What is the difference in monitoring between UFH and LMWH?

A

UFH has to be monitored using PTT

LMWH doesn’t have to be monitored

31
Q

What is the administration of UFH and LMWH?

A

UFH: IV bolus then IV infusion

LMWH: s/c injection once or twice a day (can be used at home)

32
Q

What are the half-lives of UFH and LMWH?

A

UFH: 30mins, 2hrs at higher doses

LMWH: 2hrs

33
Q

State three indications for using heparins

A
  • Bridging agent before warfarin for DVT, PE and AF prophylaxis
  • Anticoagulation after major surgery
  • During pregnancy as it doesn’t cross the placenta
  • After an MI or unstable angina
34
Q

State two adverse effects of heparins

A
  • Bruising and bleeding
  • Heparin-induced thrombocytopenia due to an autoimmune reaction (HIT) more likely with UFH
  • Osteoporosis (rare, higher risk with UFH and pregnancy)
35
Q

How can you reverse heparin?

A

Give protamine sulphate - dissociates heparin from antithrombin III

Greater effect with UFH and LMWH

36
Q

What is the MoA of fondaparinux?

A

Selectively inhibits Xa by binding to ATIII

37
Q

Name a direct acting oral anticoagulant

A

Apixiban
edoxaban
rivaroxaban

38
Q

What is the MoA of DOACs?

A

Inhibits both free Xa and Xa bound to ATIII

39
Q

Name a direct thrombin inhibitor

A

Argatroban

Dabigartran

40
Q

How can you reverse warfarin?

A

VitK

Prothrombin complex concentrate

41
Q

What is the MoA of the anti-fibrinolytic tranexamic acid?

A

Inhibit the activation of plasminogen

Can be used in menorrhagia, PPH

Pharm OTL (18 decks)

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