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Haematology BL > Antiplatelets - BB > Flashcards

Antiplatelets - BB Flashcards

1
Q

4 Classes of antiplatelet agents:

A
  1. Aspirin (NSAIDs)
  2. ADP Blockers
  3. IIb/IIIa Inhibitors
  4. Phosphodiesterase inhibitors
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2
Q

Targets for antiplatelet drugs:

A
  1. Thromboxane A2 (TXA2)
  2. ADP
  3. cAMP reduction - via ADPIIb/IIIa receptor blockers
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3
Q

Aspirin MOA:

A

Inhibits cyclooxygenase (COX1+2)

Which blocks the conversion of arachadonic acid to TXA2

TXA2 is a powerful platelet activator

(COX also converts arachadonic acid to prostaglandins - which is where it gets its analgesic effects)

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4
Q

3 Eicosanoids groups

A

All converted from arachidonic acid

  1. Leukotrienes (by Lipoxygenase)
  2. Thromboxanes (COX)
  3. Prostaglandins (COX)
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5
Q

Which eicosanoid mediates many of the effects we associate with inflammation?

A

PGE2

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6
Q

Difference between Aspirin and other NSAIDs for antiplatelet activaity

A

Aspirin irreversibly inhibits COX-1/-2 enzyme

Other nsaids reversibly inihibit them

Means that aspirin is preferred as its activity is for the lifetime of the platelet

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7
Q

Examples of other NSAIDs (x5)

A 
Ibuprofen
Naproxen
Indomethacin
Ketorolac
Diclofenac
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8
Q

Common uses for aspirin

A

Coronary disease:

  • Acute MI/ Unstable angina
  • Secondary prevention

Stroke:

  • Acute ischaemic stroke
  • Secondary prevention
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9
Q

Adverse effects of aspirin

A
  • Bleeding
  • Gastritis/ulcers (like all NSAIDs)

*Tinnitus
Caused by salicylate (aspirin metabolite - salicylic acid)
Alters cochlear nerve function
RARE - usually occurs with very high doses - and resolves when discontinued

*Reye’s syndrome:
* Severe adverse effect
* Liver failure and encephalopathy
* Associated with use in children - therefore not given to kids (except in kawasaki)

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10
Q

Thienopyridines: (name 3 drugs)

A

Ticlopidine
Clopidogrel
Prasugrel

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11
Q

Thienopyridines - mechanism of action and general uses

A

Irreversible P2Y12 receptor blockers
Blocks effects of ADP on platelets

USES:

  • Used in aspirin allergy
  • Added to aspirin in prevention of MI, Stroke
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12
Q

Adverse effects of thienopyridines:

A

Major adverse effect is bleeding

TTP - Rare dangerous side effect (strongest association with ticlopidine)

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13
Q

TTP as an adverse event from thienopyridines

A

Severe thrombocytopenia
MAHA
Neurologic abnormalitites
deficient activity of ADAMTS13 - some suggest antibodies to it

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14
Q

Ticagrelor - general

A

Cyclo-pentyl-triazolo-pyrimidine (CPTP)

Not associated with TTP

Similar mechanism of action as the theinopyridines - however different structure
Causes reversible inhibition of the P2Y12 - (ADP) receptor blockers

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15
Q

Unique side effect of ticagrelor

A

Dyspnea - mechanism unclear

also not associated with TTP

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16
Q

Phosphodiesterase inhibitors: (name the 2 drugs)

A

Dipyridamole

Cilostazole

17
Q

PDE Inhibitor mechanism of action:

A

inhibits PDE III in platelets

  • PDE breaks down cAMP
  • Therefore inhibition leads to increased cAMP
  • Increased cAMP leads to decreased platelet activation
18
Q

Dipyridamole - mechanism of action

A
  1. PDEIII inhibitor – Inhibits platelet activation
  2. Also bocks adenosine uptake by cells (vasodilation)
    - Adenosine is a vasodilator
    - reduced uptake - raises adenosine levels in blood
    - Causes vasodilation
19
Q

Uses of Dipyridamole:

A
  1. Used with aspirin for stroke prevention - (antiplatelet)
  2. Used in chemical cardiac stress testing - (vasodilator)
    • In ptx who are unable to walk on treadmill for a conventional stress test
    • Vasodilation can be used to induce coronary steal
20
Q

Cilostazol - mechanism of action

A

PDEIII inhibitor - inhibits platelet activation

Also raises cAMP in vascular smooth muscle (vasodilator)

Rarely used for antiplatelet effects - but used for vasodilator effects

21
Q

Cilostazol - uses

A

Used as a vasodilator in peripheral arterial disease - to reduce symptoms of claudication

Rarely used for antiplatelet effects

22
Q

Side effects of PDE inhibitors:

A

Many side effects related to vasodilation:

  • Headache : meningeal vasodilation
  • Flushing
  • Hypotension
23
Q

IIb/IIIa Receptor blockers (name the drugs)

A

Abciximab

Eptifibatide

Tirofiban

24
Q

IIb/IIIa Receptor blockers - mechanism of action

A

Bind and block IIb/IIIa receptors

Abciximab - is a Fab fragment of antibody to the receptor

25
Q

IIb/IIIa Receptor blockers - uses

A

All 3 drugs are used as:
- IV drugs in ACS and stenting

Risk of thrombocytopenia within hours of administratoin
- Must monitor platelet count after administration

Haematology BL (14 decks)

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