Episode 6 Anticoagulants, Thrombolytics (Fibrinolytics), Antiplatelet Agents and Antifibrinolytics

Question 1

What are the four major categories of Anticoagulants?

Answer 1

Indirect Thrombin Inhibitors (heparin), Coumarin Anticoagulants (warfarin), Direct Thrombin Inhibitors, and Direct Factor X Inhibitors

Question 2

Why can’t heparin be administered orally?

Answer 2

It is a protein which will be broken down in the GI tract

Question 3

What are the two most common heparin preparations?

Answer 3

Ufractionated heparin (UFH) - Heparin Sodium.
Low-molecular-weight heparin (LMWH) - Fragmin, Innohep, Lovenox

Question 4

How does heparin work?

Answer 4

It stimulates Antithrombin, which shuts down FX (and other clotting factors as well)

Question 5

What does the lack of thrombin result in?

Answer 5

Inability to convert fibrinogen into fibrin

Question 6

Why is heparin called an indirect thrombin inhibitor?

Answer 6

B/c stimulates Antithrombin to inhibit FX, which inhibits, Prothrombin from becoming thromobin. Without thrombin there is no fibrin conversion from fibrinogen. Therefore it is an indirect inhibitor

Question 7

What does heparin stimulate also besides antithrombin?

Answer 7

Heparin cofactor II (which inhibits thrombin)

Question 8

Why is UFH monitored with APPT?

Answer 8

UFH response varies greatly among patients

Question 9

What is the main difference in how UFH and LMWH can be used?

Answer 9

UFH is mainly used in hospitals and LMWH can be used both in hospital or on an outpatient basis

Question 10

How are LMWH administered?

Answer 10

Subcutaneously but not intravenous

Question 11

What is the difference between UFH and LMWH?

Answer 11

UFH is isolated from different animals and vary in size. LMWH is selected for small (low molecular weight) heparins. LMWH will not interact (thereby reducing its anticoagulation effectiveness) with plasma proteins as much as UFH.

Question 12

T/F LMHWs do not need to be monitored with lab tests such as APPT, while UFH do.

Answer 12

T

Question 13

T/F Warfarin is found in rodent poison

Answer 13

T

Question 14

How does warfarin affect the blood clotting cascade?

Answer 14

It works in the liver by preventing the liver to make vitamin K dependent clotting factor (II, VII, IX, X)

Question 15

What is warfarin used for prophylactially?

Answer 15

Venous thrombosis and Pulmonary Embolism

Question 16

What is the ideal INR for someone taking warfarin?

Answer 16

2.0-3.0 - a balance between reducing clot formation and not causing spontaneous bleeding

Question 17

What is a major disadvantage of warfarin?

Answer 17

Has many drug-drug interactions

Question 18

What is a common effect of DDIs on warfarin?

Answer 18

Inhibition of warfarin breakdown (INR will go up very high)

Question 19

Which two drugs stimulate warfarin metabolism?

Answer 19

Chronic alcohol use and Phenytoin (Dilantin)

Question 20

What effects do oral contraceptive have on warfarin?

Answer 20

Increase synthesis of many clotting factors and can reduce the effects of warfarin

Question 21

What effects to foods rich in vitamin K (green leafy vegetables and cereals) have on warfarin?

Answer 21

Decrease effects of warfarin by stimulating synthesis of vitamin K dependent clotting factor

Question 22

How can warfarin overdoses be treated?

Answer 22

with vitamin K and transfusions

Question 23

Why is warfarin contraindicated during pregnancy?

Answer 23

It can cross the placenta and is teratogenic (causes birth defects)

Question 24

What is the first direct thrombin inhibitor to come on to the market?

Answer 24

Pradaxa (dabigatran)

Question 25

What is the advantage of dabigatran over warfarin?

Answer 25

Do not required INR tests

Question 26

Any drug that ends in xaban is what kind of drug?

Answer 26

Direct Factor X inhibitor - rivaroxaban, apixaban, edoxaban

Question 27

How are thrombolytics usually administered?

Answer 27

IV, they catalyze the formation of plasmin from plasminogen

Question 28

What do thrombolytics activate?

Answer 28

tPA (tissue plasminogen activator)

Question 29

What are the three main classes of antiplatelet agents?

Answer 29

Cyclooxygenase inhibitors (aspirin), Thienopyridines (ADP Inhibitors), and GPIIb/IIIa inhibitors

Question 30

What does aspirin shut down?

Answer 30

Cycloxygenase enzyme is shutdown and platelets do not make their prostaglandin TXA2 (helps make platelets more sticky and more likely to aggregate)

Question 31

How do thienopyridines work?

Answer 31

prevent binding of ADP to its receptors on platelets, inhibiting a pathway that leads to platelet aggregation

Question 32

How are GPIIb/III inhibitors administered?

Answer 32

Administered via IV

Question 33

How do antifibrinolytics like tranexamic acid work?

Answer 33

They inhibit the activation of plasminogen to plasmin, prevent the destruction of clots, help to stop bleeding in patients with prolonged bleeding time

Question 34

What has a higher risk of death, withholding warfarin or continuing warfarin during most dental procedures?

Answer 34

Withholding increases risk of death more than continuing

Question 35

What is the recommended INR before dental procedures for someone on warfarin?

Answer 35

Less than 4

Question 36

Which antifibrinolytic is often recommended over tranexamic acid?

Answer 36

Aminocaproic acid, easier to make and less expensive