5: Anticoagulant drugs

Question 1

Which clotting times are used to monitor

a) warfarin
b) heparin

activity?

Answer 1

a) INR (which is a standardised method of measuring PT)
b) APTT

Question 2

What are two indications for anti-coagulant drugs?

Answer 2

Venous thrombosis

Atrial fibrillation (increases likelihood of thrombosis)

Thrombophilia

Question 3

Atrial fibrillation can cause (venous / arterial) thrombosis.

Answer 3

either

depending on heart chamber where the blood clots

Question 4

What blood components are activated in

a) venous thrombosis
b) arterial thrombosis?

Answer 4

a) Fibrin

b) Platelets

Question 5

Because of their short half life, Protein C and S levels drop first when a patient is given anticoagulant drugs.

What is the effect of this?

Answer 5

Increased risk of thrombosis (temporary)

Question 6

Which anticoagulant drug enhances the activity of antithrombin?

Answer 6

Heparin

Question 7

What are the two forms and routes of administration of heparin?

Answer 7

Unfractionated heparin (IV)

LMWH (subcut)

Question 8

Name an example of LMWH?

Answer 8

Dalteparin sodium

Question 9

Heparin enhances the activity of ___.

Answer 9

antithrombin

Question 10

Heparin potentiates the activity of antithrombin, a protein which inactivates clotting factors.

Unfractionated heparin enhances the activity of antithrombin against ___.

LMWH enhances the activity of antithrombin against ___.

Answer 10

unfractionated: thrombin

LMWH:Xa

Question 11

Which anticoagulant drugs are monitored using

a) INR
b) APTT?

Answer 11

a) Warfarin

b) Heparin

Question 12

Which clotting time is used to monitor the activity of unfractionated heparin?

Answer 12

APTT

Question 13

Does LMWH require monitoring?

Answer 13

No

But you can using Anti-Xa assay

Question 14

What is the main side effect of heparin?

Answer 14

Bleeding

Question 15

Heparin can trigger an autoimmune reaction causing which deficiency?

Answer 15

Thrombocytopaenia

Question 16

Name three side effects of heparin.

Answer 16

Bleeding

Thrombocytopaenia (autoimmune)

Osteoporosis (long term use)

Question 17

What happens if you overdose a patient on heparin?

Answer 17

Bleeding

Question 18

Heparin has a (short / long) half life.

Answer 18

short half life

so if bleeding or requiring a procedure you can just stop it

Question 19

In emergencies, which drug can be used to reverse the effects of heparin?

Answer 19

Protamine sulphate

Question 20

Which clotting factors does

a) unfractionated
b) LMW

heparin act on?

Answer 20

a) Thrombin

b) Xa

Question 21

Which anticoagulant drug inhibits the action of Vitamin K?

Answer 21

Warfarin

Question 22

What is the mechanism of action of warfarin?

Answer 22

Inhibits action of Vitamin K

REDUCING ACTIVATION FACTORS II, VII, IX AND X

Question 23

Where are clotting factors produced?

Answer 23

Liver

Question 24

What is required for the production of factors II, VII, IX and X in the liver?

Answer 24

Vitamin K

Question 25

Do patients on warfarin still produce clotting factors? What is the significance of this?

Answer 25

**Yes** **The clotting factors are non-functional, need to be activated by Vitamin K** Vitamin K can be used to reverse the effects of warfarin

Question 26

**Warfarin** has a **narrow ___ \_\_\_.**

Answer 26

**therapeutic index**

Question 27

Which family of enzymes **metabolises** warfarin in the liver?

Answer 27

**Cytochrome P450**

Question 28

**Warfarin dosage** depends on what?

Answer 28

**Patient's INR after first dose of 5 - 10 mg** i.e liver clearance of warfarin by CYP450

Question 29

When should **warfarin** be taken?

Answer 29

**Same time every day**

Question 30

Which clotting time is used to measure warfarin response?

Answer 30

**INR** Which is a different way of measuring PT

Question 31

Which clotting factors does warfarin affect?

Answer 31

**II** **VII** **IX** **X**

Question 32

What is **INR?**

Answer 32

**International normalised ratio** **Standardised method of measuring a prothrombin time** since people were using different reagents to do the test

Question 33

What is the main side effect of warfarin?

Answer 33

**Bleeding**

Question 34

**Warfarin** ___ with other drugs.

Answer 34

**interacts**

Question 35

Which **substance** inhibits the liver's ability to metabolise warfarin?

Answer 35

**Alcohol** Alcohol intake increases bleeding risk in patients on warfarin

Question 36

What is the **half life** of warfarin compared to **heparin?** What does this mean in the context of bleeding?

Answer 36

**T1/2 warfarin \> T1/2 heparin** Omitting warfarin won't control bleeding as effectively as heparin omission

Question 37

**Apart from stopping warfarin**, what can be done to reverse warfarin overdose?

Answer 37

**Vitamin K PO / IV** **Clotting factors (give FFP)**

Question 38

Why is **warfarin omission** and **oral Vitamin K** attempted before giving warfarin patients clotting factors via FFP?

Answer 38

**Exposure to BBVs** (inc. ones we don't know about)

Question 39

How long does **Vitamin K** require to take effect?

Answer 39

**6 hours** ish

Question 40

How long does **FFP** require to take effect?

Answer 40

**Immediate**

Question 41

Which **clotting factor** does **rivaroxaban** act on?

Answer 41

**Xa** 'xa' in the name hints that the drug is a Factor Xa inhibitor

Question 42

Which clotting factor does **dabigatran** ​act on?

Answer 42

**Thrombin**

Question 43

Which clotting factor do rivaroxaban, apixaban and edoxaban ​act on?

Answer 43

**Xa** 'xa' in the name

Question 44

**How are NOACs taken?**

Answer 44

**PO**

Question 45

What is an **a) advantage** **b) disadvantage** of using NOACs versus warfarin?

Answer 45

**a) Arguably more effective; No monitoring required** **b) No antidote**

Question 46

**Protamine sulphate** is used to reverse **(heparin / warfarin)** overdose.

Answer 46

**heparin overdose**

Question 47

**Vitamin K** is used to reverse **(heparin / warfarin)** overdose.

Answer 47

**warfarin overdose**