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Pharmacology > Anti-platelets and Thombolytics > Flashcards

Anti-platelets and Thombolytics Flashcards

1
Q

Give some examples of anti-platelet drugs

A

Aspirin

Di-pyridamole

Clopidogrel

Glycoprotein IIb/IIIa inhibitors

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2
Q

How does aspirin work as an anti-platelet?

A

Irreversible COX-1 inhibition by covalent acetylation of serine

Stops production of prostaglandin 2 and therefore thomboxane A2

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3
Q

How does clopidogrel work?

A

Inhibits ADP-dependent aggregation of platelets

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4
Q

Indications of clopidogrel?

A

Acute coronary syndrome - MI, angina

After a PCI (percutaneous coronary intervention)

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5
Q

How does dipyridamole work as an antiplatelet?

A

Phosphodiesterase inhibitor

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6
Q

ADRs of dipyridamole and why?

A

Positive inotrope and vasodilator

  • flushes
  • headaches
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7
Q

Indication for dipyridamole?

A

Secondary prevention of stroke

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8
Q

How do glycoprotein IIb/IIIa antagonists work?

A

Fibrinogen normally binds to these receptors causing platelet aggregation
Antagonists block this final pathway

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9
Q

Name some glycoprotein IIb/IIIa antagonists

A

Abciximab
Eptifibatide
Tirofiban

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10
Q

Uses of glycoprotein IIb/IIIa receptor antagonists?

A

High risk acute coronary syndrome
Post-PCI
-increases risk of bleeding compeicatioms but decreases acute thrombosis and re-stenosis

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11
Q

How are thrombi normally cleared?

A

Plasmin activated from plasminogen cleaves fibrin by binding to fibrin strands within a thrombus

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12
Q

How is plasminogen cleaved to plasmin?

A

Plasminogen activators

  • tissue plasminogen activator (tPA)
  • urokinase-type plasminogen activator (uPA)

Activate plasminogen that is bound to fibrin

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13
Q

What regulates the fibrinolytic system?

A

Circulating inhibitors such as PAI-1

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14
Q

Mechanism of action of streptokinase?

A

Promotes cleavage in plasminogen to produce plasmin

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15
Q

Why can streptokinase not be used twice in the same patient?

A

It is a bacterial protein so is antigenic

Generates blocking antibodies which persist for many years leading to allergic reactions

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16
Q

Other ADRs of streptokinase?

A

Transient hypotension when being infused (slow infusion to increase blood pressure)
Haemorrhage

17
Q

What is alteplase? Mechanism of action?

A

A recombinant tPA

Converts plasminogen to plasmin when plasminogen is bound to fibrin - clot-specific as only works in presence of fibrin

18
Q

Indications for fibrinolytic drugs?

A

Acute MI
PE
Major venous thrombosis
Ischaemic stroke

19
Q

Why must fibrinolytics be given within a short amount of time if the event?

A

Consequence of vascular occlusion can become irreversible

Thrombi become more resistant to lysis so that potential benefit decreases while risk of haemorrhage (stroke) remains the same

20
Q

How long can fibrinolytics be given given for after an event?

A

Ischaemic stroke - up to 3 hours

Coronary occlusion - up to 12 hours

21
Q

Difference between fibrinolytics and thrombolytics?

A

Fibrinolytics breakdown fibrin inside a thrombus eg streptokinase, alteplase (tPA)

Thombolytics break down the thrombus eg heparin

22
Q

Criteria for a fibrinolytic therapy to be given to a patient who has had an MI?

A

Clear evidence from history and ECG of MI within last 12 hours
No contra-indications

23
Q

Criteria for fibrinolytic treatment in PE?

A

Clear diagnosis
Significant haemodynamic compromise
Absence of major contraindications

24
Q

Contra-indications of fibrinolytics?

A

Active peptic ulcer or other potential bleeding source
Recent trauma/surgery
History of cerebral haemorrhage or stroke of uncertain aetiology
Uncontrolled hypertension
Coagulation defect
Streptokinase should not be given to a patient twice

25
Q

ADRs with fibrinolytics?

A

Haemorrhage

  • brain
  • GI tract
26
Q

Treatment of severe allergy/anaphylaxis to streptokinase?

A 
Adrenaline
Oxygen 
IV fluids 
Antihistamine
Hydrocortisone
27
Q

Treatment of a cerebrovascular event after fibrinolytic therapy?

A

CT or MRI to find out cause
-haemorrhagic - treatment related
-ischaemic - embolus from heart
Both equally likely after MI

28
Q

Treatment of serious bleeding after fibrinolytic therapy?

A

Blood transfusion or volume expanders
Inhibition of further fibrinolysis with tranexamic acid or aprotinin
Specific recombinant or pooled clotting factors

29
Q

What are the different ways that anti-platelets can work?

A

Stop platelet adhesion
Stop platelet activation
Stop platelet aggregation

Pharmacology (23 decks)

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