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Sem 5 Pharm > Anticoagulants/Antiplatelets > Flashcards

Anticoagulants/Antiplatelets Flashcards

1
Q

Warfarin is metabolised how?

A

Hepatic metabolism- by CYP450 enzyme

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2
Q

What is Warfarins distribution once absorbed?

A

Heavily protein bound to albumin 99%

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3
Q

What drugs would increase the conc of warfarin in the blood? (2 mechanisms)

A

By displacing warfarin bound to albumin- NSAIDs

By inhibiting CYP450- cimetidine, amiodarone, alcohol, metronidazole

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4
Q

How long is Warfarins onset of action?

A

Slow and so may need heparin to cover initially

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5
Q

How fast or slow is Warfarins offset?

A

Half life ~48 hrs

Therefore need to stop 3 days prior to surgery to allow for making of new clotting factors

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6
Q

Side effects of Warfarin

A

Bleeding, epistaxis, GI bleeding, intracranial

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7
Q

How can you reverse warfarin?

A

Parenteral vitamin K (acts slowly)
Fresh frozen plasma (acts quickly)
Can also give Prothrombin Complex Concentrate (ii, ix, x)

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8
Q

What cautions do you need to be wary of with warfarin?

A

Teratogenic in 1st trimester

Can cause brain haemorrhage in 3rd trimester

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9
Q

What is INR?

A

Patients prothrombin time OVER average prothrombin time

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10
Q

Which common drugs should be avoided in warfarin use?

A

Antiepileptics
St Johns Wort
Rifampicin

(All induce hepatic enzymes)

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11
Q

Mechanism of action of warfarin?

A

Vitamin K antagonist.

Vitamin K is needed for the production of active factors II, VII, IX, X

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12
Q

What is Virchow triad?

A

Hypercoaguability
Blood stasis
Endothelial damage

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13
Q

Mechanism of action of heparin

A

Binds reversibly to anti-thrombin therefore
Almost instant inactivation of factors IIa, Xa
Therefore prevents progression of existing clots

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14
Q

Name two examples of a LMWH

A

Dalteparin

Enoxaparin

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15
Q

Give three advantages of LMWH over unfractionated

A 
Absorbed better/better absorption predictability
Higher bioavailability (90%)
More predictable dose response curve
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16
Q

Name three negatives of unfractionated heparin

A

Non linear dose response curve
Poor absorption from gut therefore needs to be IV or SC
Can’t be eliminated in haemodialysis

17
Q

Name three adverse drug reCtions of unfractionated heparin

A

Bruising/bleeding
Osteoporosis
Thrombocytopenia (immune phenomenon)

18
Q

How can you reverse heparin?

A

Stop the heparin asap

Use Protamine Sulfate (dissociates the heparin from the antithrombin)

19
Q

Name an advantage of LMWH over warfarin

A

Is safe to use in pregnancy

20
Q

Name three DOACs

A

Rivoroxaban
Apixaban
Dabigatran

21
Q

What is the mechanism of action of Rivoroxaban

A

Competitive antagonist of factor Xa

22
Q

What is the mechanism of action of Dabigatran

A

Competitive antagonist of Thrombin

23
Q

Name a positive of DOACs

A

No monitoring required
No antidote available
Have more predictable pharmacokinetics

24
Q

Name one drug you should avoid while taking Dabigatran

A

PPI

they reduce absorption

25
Q

How are DOACs excreted?

A

Renal

Therefore in renal exposure, you will get increased drug exposure

26
Q

Name three anti-platelet drugs

A

Aspirin
Clopidogrel
Dipyridamole

27
Q

Mechanism of action of aspirin

A

Irreversibly binds to COX enzyme
COX produces pro-inflammatory prostaglandins and thromboxanes
Thromboxanes facilitate platelet aggregation

28
Q

Side effects of aspirin

A

Bronchospasm
GI upset
Hypersensitivity reactions

29
Q

Contraindications of aspirin

A

Asthma
Peptic ulcer
If pt has hypersensitivity to NSAID

30
Q

Mechanism of action of clopidogrel

A

Prevents binding of ADP to platelet receptor which stops the cross linking of fibrin

31
Q

How is clopidogrel metabolised?

A

Clopidogrel is a pro drug that is metabolised by CYP450 to become active.
Then metabolised by the liver

32
Q

Side effects of clopidogrel

A

Abdo pain
Diarrhoea
Dyspepsia
Bleeding disorder

33
Q

How is clopidogrel excreted

A

50% renal, 50% excreted

34
Q

What is the half life of aspirin

A

15 minutes but then increases as the dose increases

35
Q

Mechanism of action of dipyridamole

A

Adjunct to other antiplatelets

Phsophodiesterase inhibitor, prevents breakdown of cAMP, cAMP usually inhibits platelet function.

36
Q

Metabolism of dipyridamole

A

Hepatic and excreted with bile

37
Q

Side effect of dipyridamole

A

Positive inotrope and vasodilator(tf flushing and headaches)

Sem 5 Pharm (10 decks)

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