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Pharmacodynamics > Heparin > Flashcards

Heparin Flashcards

1
Q

Where is heparin found in the body?

“BE SPECIFIC.”

A

They are found in the mast cells of the lungs // liver // intestinal mucosa.

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2
Q

What is the charge of a heparin molecule?

A

Negative.

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3
Q

By how much does heparin INCREASE anti-thrombin activity?

A

By x2,000 to x10,000

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4
Q

What components does heparin act on?

A 
Antithrombin
Thrombin
IXa
Xa
XIa
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5
Q

What is the purpose of heparin?

A

It is a blood thinner = Known as an anticoagulant.

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6
Q

What type of site does anti-thrombin have?

A

Positively charged LYSINE sites.

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7
Q

What happens when heparin binds to anti-thrombin?

A

A conformational change in anti-thrombin occurs.

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8
Q

What does Factor IIa need to bind to in order form a complex?

A

Needs to bind to active site of arginine and heparin in order to form a complex.

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9
Q

What happens after a factor IIa complex is formed?

A

Removed by an endothelial system.

Then, heparin leaves (INTACT) in order to bind to more in the future.

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10
Q

What is the key difference for Factor Xa when it’s binding in order to form a complex?

A

Heparin ONLY needs to react with anti-thrombin.

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11
Q

What is fractionation?

A

This is when unfractionated heparin is MODIFIED in order to reduce the size of polysaccharide chains.

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12
Q

What is the name given for heparin molecules which undergo fractionation?

A

Low molecular weight heparin (LMWH).

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13
Q

Name the 3 main LMWH products used commercially.

A

Enoxaparin
Tinzaparin
Dalteparin

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14
Q

How is enoxaparin formed?

A

Benzylation followed by alkaline depolymerisation.

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15
Q

How is tinzaparin formed?

A

Enzymatic depolymerisation.

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16
Q

How is dalteparin formed?

A

Nitrous acid depolymerisation.

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17
Q

What is the mean molecular weight of LMWH molecules?

A

4 - 5 kDa.

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18
Q

What is the mean molecular weight of unfractionated heparin?

A

10 - 40 kDa.

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19
Q

Which out of UFH and LMWH has the higher bioavailability?

A

LMWH

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20
Q

What is the main route of administration for unfractionated heparin?

A

Intravenous Infusion

21
Q

What is the main route of administration for LMWH?

A

Subcutaneous Injection

22
Q

What is the half life for LMWH?

A

4 - 6 hours -> thus, has a SLOWER renal clearance.

23
Q

What is heparin induced thrombocytopenia?

A

This is the development of a LOW platelet count.

24
Q

Where is LMWH metabolised?

A

The liver.

25
Q

What happens to the duration and effect when the dosage shifts from low to therapeutic?

A

There is an increase in duration and effect.

26
Q

By how much is the effect of subcutaneous injection delayed?

A

1 - 2 hours.

27
Q

What is the difference in terms of duration between iv and sc administration?

A

Subcutaneous injection is short term compared to iv infusion.

28
Q

What is thromboprophylaxis?

A

This is a medical treatment to prevent development of thrombosis.

29
Q

What is APTT?

A

It is blood test which characterises coagulation of the blood.
Thus, measures how LONG it takes for a clot to form.

30
Q

What is ACT?

A

This measures the activated clotting time.

31
Q

What is reflected by the administration of anti Xa?

A

Reflects the concentration of heparin in the patients plasma.

32
Q

When is monitoring required in terms of administering Anti Xa?

A

When the patient has:

  • Extreme Body Weight
  • Renal Impairment
33
Q

What are the 4 adverse reactions of heparin treatment?

A

HIT
Osteopenia
Injection Site Reactions
Bleeding

34
Q

What is HIT?

A

This is when there is a LOW platelet count.

35
Q

What is the scoring system for HIT?

A

4T scoring system = 2 points per factor.

  • Thrombocytopenia
  • Thrombosis
  • Timing
  • Other causes of thrombocytopenia
36
Q

What are the other causes of thrombocytopenia?

A

Septicaemia

37
Q

What happens if the HIT score is greater than 4?

A

Heparin is stopped and instead an alternative anticoagulant is given.

38
Q

What is an alternative anticoagulant given?

A

Argatroban

39
Q

What is the optimal timing for viewing the results of heparin administration?

A

5 days after starting heparin.

40
Q

Why can heparin induced thrombocytopenia (HIT) occur?

A

This is due to the body producing an IgG antibody towards heparin.

41
Q

What is osteopenia?

A

This is the thinning of the bones due to dose and duration.

42
Q

What can occur due to injection site reactions?

A

Bleeding
Ecchymosis
Erythema
Skin Necrosis

43
Q

What is ecchymosis?

A

Easier bruising

44
Q

What is erythema?

A

Redness of the skin

45
Q

In terms of bleeding, which type of heparin produces LESS bleeding as an adverse reaction?

A

LMWH.

46
Q

What partially reverses LMWH?

A

Protamine.

47
Q

What are the side effects of taking protamine?

A

Hypotension

Bradycardia

48
Q

Who can’t take protamine?

A

Those allergic to fish as it’s made from fish sperm.

Pharmacodynamics (21 decks)

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