Fibrinolytics

Question 1

What is haemostasis?

Answer 1

Cessation of blood loss from a damaged vessel.

Question 2

What is thrombosis?

Answer 2

A pathological condition resulting from inappropriate activation of haemostatic mechanisms.

Question 3

What characterizes venous thrombosis?

Answer 3

Usually associated with stasis of blood; small platelet component and large component of fibrin.

Question 4

What characterizes arterial thrombosis?

Answer 4

Usually associated with atherosclerosis; large platelet component.

Question 5

Define thrombus.

Answer 5

A blood clot formed in situ within the vascular system, impeding blood flow.

Question 6

What is the role of thrombin in blood clotting?

Answer 6

Converts soluble fibrinogen to an insoluble meshwork of fibrin.

Question 7

What are the two limbs of the clotting cascade?

Answer 7

In vivo (extrinsic) pathway - Rapid; in vitro (intrinsic) pathway - Slow.

Question 8

What is the function of calcium ions in coagulation?

Answer 8

Essential for activation of factors IXa, VIIa, and Xa.

Question 9

What is haemophilia A caused by?

Answer 9

Lack of factor VIII.

Question 10

What is the primary use of antithrombotic drugs?

Answer 10

To treat thrombosis.

Question 11

What are the three classifications of antithrombotic drugs?

Answer 11

• Antiplatelet drugs
• Anticoagulants
• Fibrinolytic agents

Question 12

What is the action of heparin?

Answer 12

Inhibits plasma antithrombin III.

Question 13

What are common adverse effects of heparin?

Answer 13

• Bleeding
• Thrombocytopaenia
• Hypersensitivity reactions
• Osteoporosis

Question 14

What is the mechanism of action of low molecular weight heparins?

Answer 14

Accelerates action of antithrombin III, increasing inactivation of factor Xa.

Question 15

What is the main use of direct thrombin inhibitors?

Answer 15

Directly inhibit thrombin without relying on antithrombin III.

Question 16

What is dabigatran used for?

Answer 16

Prevention of venous thromboembolism and stroke in atrial fibrillation.

Question 17

What is the mechanism of action of warfarin?

Answer 17

Inhibits the reduction of vitamin K, preventing carboxylation of factors II, VII, IX, and X.

Question 18

What is streptokinase and its primary use?

Answer 18

A plasminogen activating protein used to reduce mortality in acute myocardial infarction.

Question 19

What are the adverse effects of streptokinase?

Answer 19

• Nausea
• Headache
• Dizziness
• Low blood pressure
• Mild fever
• Bleeding

Question 20

What is epsilon amino-caproic acid (EACA)?

Answer 20

A lysine analogue that inhibits plasminogen activation and is used to check fibrinolysis associated bleeding.

Question 21

What is the treatment for overdose of heparin?

Answer 21

Protamine sulfate.

Question 22

Fill in the blank: The drug _______ is a recombinant tissue plasminogen activator.

Answer 22

Alteplase

Question 23

True or False: Direct thrombin inhibitors require monitoring of activated partial thromboplastin time (aPTT).

Answer 23

False

Question 24

What is the primary indication for using antifibrinolytic drugs?

Answer 24

To counteract the effect of fibrinolytic agents and bleeding due to their use.

Question 25

What can rapid intravenous injection of certain drugs cause?

Answer 25

Hypotension, bradycardia, and possible arrhythmias.

Question 26

What is a limitation of the large dose needed for specific treatments?

Answer 26

Tranexamic acid is mostly preferred.

Question 27

What is the initial priming dose of tranexamic acid?

Answer 27

5 g oral/i.v., followed by 1 g hourly till bleeding stops (max. 30 g in 24 hrs).

Question 28

What is the mechanism of action of tranexamic acid?

Answer 28

Inhibits plasminogen activation and thus prevents fibrinolysis.

Question 29

List some clinical uses of tranexamic acid.

Answer 29

* Treat bleeding or risk of bleeding following prostatectomy or dental extraction * Menorrhagia (excessive menstrual blood loss) * Life-threatening bleeding following thrombolytic drug administration.

Question 30

How much more potent is tranexamic acid compared to EACA?

Answer 30

7 times more potent.

Question 31

What are the main side effects of tranexamic acid?

Answer 31

* Nausea * Diarrhoea.

Question 32

What can occur infrequently as a side effect of tranexamic acid?

Answer 32

* Thromboembolic events * Disturbed colour vision * Allergic reactions.

Question 33

What is the typical dosage range for tranexamic acid?

Answer 33

10–15 mg/kg 2–3 times a day or 1–1.5 g TDS oral, 0.5–1 g TDS by slow i.v. infusion.

Question 34

What are antiplatelet drugs used for?

Answer 34

Interfere with platelet function and are useful in the prophylaxis of thromboembolic disorders.

Question 35

What receptors do platelets express on their surface?

Answer 35

Several glycoprotein (GP) integrin receptors.

Question 36

What happens when reactive proteins like collagen react with platelet receptors?

Answer 36

Platelet activation and release of pro-aggregatory and vasoconstrictor mediators.

Question 37

What forms a 'platelet plug' in arteries?

Answer 37

The binding of fibrinogen and von Willebrand factor (vWF) to platelet GPIIb/IIIa receptors.

Question 38

In which type of thrombosis are antiplatelet drugs more useful?

Answer 38

Arterial thrombosis.

Question 39

Which substance synthesized in the intima of blood vessels inhibits platelet aggregation?

Answer 39

Prostacyclin (PGI2).

Question 40

What is the role of platelets in atherogenesis?

Answer 40

They play a role in atherosclerotic plaque formation leading to coronary artery heart disease.

Question 41

What is the mechanism of action of aspirin as an antiplatelet drug?

Answer 41

Inhibits cyclo-oxygenase irreversibly and inhibits platelet thromboxane (TX)A2 synthesis.

Question 42

What are the gastrointestinal side effects of aspirin?

Answer 42

Irritation of the stomach lining, gastrointestinal upset, ulcers, and bleeding.

Question 43

What is clopidogrel and how does it function?

Answer 43

A prodrug that irreversibly inhibits P2Y12 receptors and inhibits platelet aggregation.

Question 44

What is the clinical effect of clopidogrel in relation to aspirin?

Answer 44

Its clinical effect is additive with aspirin.

Question 45

What is prasugrel used for?

Answer 45

Acute coronary syndrome (ACS).

Question 46

How does ticagrelor differ from other antiplatelet drugs?

Answer 46

It is reversible but non-competitive.

Question 47

What do antagonists of GPIIb/IIIa receptors do?

Answer 47

Inhibit diverse agonists activating GPIIb/IIIa receptors.

Question 48

What is dipyridamole used for?

Answer 48

As a vasodilator for angina pectoris and in addition to aspirin for stroke or transient ischemic attack.

Question 49

List some clinical uses of antiplatelet drugs.

Answer 49

* Acute myocardial infarction * Prevention of myocardial infarction in patients at high risk * Cerebral ischemic attack (ministrokes) or thrombotic stroke * Prevent recurrence in atrial fibrillation.

Question 50

What is the primary action of antiplatelet drugs?

Answer 50

To prevent arterial thrombosis.