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Pharm block 4 hemostasis and cardiac > Heparin Anticoagulants I > Flashcards

Heparin Anticoagulants I Flashcards

1
Q

where is heparin naturally found

A

in the granules of MAST cells (along with histamine and serotonin)

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2
Q

chemically what is heparin made up of

A

strongly acidic (highly ionized) mucopolysaccharide composed of repeating units of sulfated glucuronic acid and sulfated glucosamine.

is heterogenous - found in different weights

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3
Q

what part of heparin is required to bind its co-factor

A

penta-saccaride sequence

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4
Q

why is there variation in heparin

A

comes from swine and different species produce different potencies of heparin

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5
Q

what 2 methods are used to standarize heparin

A

anti-Xa and anti-IIa assays

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6
Q

how is heparin dosed

A

in units

1 unit equals 8-12mg depending on potency

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7
Q

Actions of Heparin

A

Inhibits the action of activated factor Xa and factor IIa (Thrombin).

Inhibits the action of several other serine protease enzymes (XIIa, XIa).

Inhibits the aggregation of platelets (at high concentration).

Plasma clearing effect

Binds to vascular lining and neutralizes the positive charge.

Causes a release of Tissue Factor Pathway Inhibitor (TFPI).

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8
Q

heparin mainly affects which pathway

A

intrinsic (contact activation) pathway

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9
Q

heparin’s MOA

A

Heparin binds to AT III and induces a conformational change in AT III resulting in 1000x greater binding affinity to clotting factor proteases.

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10
Q

heparin requires what co-factor

A

antithrombin III

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11
Q

plasma clearing affect of heparin

A

Turbid plasma is rapidly cleared of fat chylomicrons by a release of lipase from the blood vessels.

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12
Q

heparin’s route of administration

A

IV and subcutaneous (mostly used inpatient)

not absorbed orally or rectally

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13
Q

APTT therapeudic range for heparin

A

2- 2.5 times baseline

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14
Q

how do you monitor heparin

A

APTT (effects are not well correlated with patient weight)

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15
Q

what enzyme metabolizes heparin

A

heparinase in the liver

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16
Q

how is heparin excreted

A

20-25% of heparin is excreted in urine

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17
Q

what happens to heparin that is not excreted

A

Some heparin is picked up by mast cells

Endothelium is able to bind heparin

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18
Q

what is the duration and onset of heparin

A

Biologic T 1/2 of intravenous heparin is 1-3 hours, depending on the dose. (dose dependent effect)

Onset of action is 5-10 minutes (as measured by APTT method).

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19
Q

Endogenous modulators of heparin action (what affects heparin’s actions)

A

AT(main heparin co-factor) needed for heparin to have affects

Heparin cofactor II (second cofactor) can only inhibit thrombin when heparin binds

Tissue Factor Pathway Inhibitor (TFPI)
Platelet factor 4 (heparin neutralizing protein)

20
Q

Side Effects of Heparin

A

Hemorrhagic complications
 (Adrenal, gut, etc.)
Heparin induced thrombocytopenia (HIT)
Osteoporotic
Alopecia

21
Q

Heparin induced thrombocytopenia (HIT)

A

Generation of antiheparin platelet factor 4 antibodies. (Ab to the complex) These antibodies activate platelets and endothelial cells.

can lead to limb loss - monitor platelet counts for drops of around 50%

22
Q

clinical uses of heparin

A 
Therapeutic anticoagulation
Surgical anticoagulation
Prophylactic anticoagulation
Unstable angina and related coronary syndromes
Adjunct therapy with thrombolytic drugs
Thrombotic and ischemic stroke
23
Q

Protamine

A

is a powerful heparin antagonist. It has a low molecular weight and is a highly basic protein found in the sperm of certain fish.

It combines with strongly acidic heparin to form a stable salt with loss of anticoagulant activity. (an advantage to using heparin is that an antagonist is available)

24
Q

how much protamine is needed to neutralized 1 unit of heparin?

A

about 10 ug

2500 units is neutralized by 25 mg

25
Q

Low Molecular Weight Heparins & Synthetic Heparin Pentasaccharide are made by

A

Prepared by fractionation or depolymerization of native heparin.

26
Q

bioavailability of LMW heparin vs heparin

A

LMW heparin 100% (advantage it can be given orally)

heparin

27
Q

Clinical Advantages of LMW Heparins

A
  • Better bioavailability
  • Longer duration of action
    Less bleeding
    Lesser thrombocytopenia
28
Q

do LMW heparins require a co-factor

A

yes! they still require AT III

29
Q

clinical uses of LMW heparin

A

Prophylaxis of DVT (once a day dosing advantage over heparin)
Treatment of DVT (can be sent home on it)
Management of acute coronary syndromes
Other uses such as anticoagulation for surgical and interventional cardiovascular procedures

30
Q

Antithrombin- Concentrates (AT) uses

A

Antithrombin-concentrate is used to treat patients with acquired or congenital antithrombin-deficiency AT is also useful in *sepsis and *disseminated intravascular coagulation

pts with AT III deficiencies are more prone to DIC and sepsis

31
Q

Hirudin

A

is a protein from the saliva of the medicinal leech (Hirudo medicinalis) which contains several pharmacologically active substances.

direct thrombin inhibitor

32
Q

refludan

A

commercial preparation of r-hirudin is used in the anticoagulant management of heparin induced thrombocytopenic patients.

33
Q

Argatroban

A

Thrombin Inhibitor, a synthetic anti-thrombin agent which is currently used as an anticoagulant in patients who can not be treated with heparin, special usage in the management of heparin induced thrombocytopenia.

34
Q

Bivalirudin

A

is a synthetic antithrombin agent. This agent is a hybrid molecule between a component of hirudin and a tripeptide. This drug is approved for PTCA anticoagulation.

used for stent placement

35
Q

LMW heparins MOA

A

Complex with AT and inhibit factors Xa and IIa

36
Q

fondaparinux (pentasaccaride) MOA

A

complex with AT and inhibits factor Xa

37
Q

argatronban MOA

A

directly inhibits IIa

38
Q

Bivalirudin MOA

A

directly inhibits IIa

39
Q

Hirudin MOA

A

directly inhibits IIa

40
Q

Antithrombin concentrate MOA

A

Directly inhibits IIa

41
Q

protamine sulface MOA

A

heparin antagonist

42
Q

Argatroban, Bivalirudin, and Hirudin indications

A

Anticoagulant management of HIT patients

43
Q

Antithrombin concentrate indications

A

DIC, sepsis, thrombophilia, hypercoagulable state

44
Q

fondaparinux (pentasaccharide) indications

A

management of a DVT

45
Q

protamine sulfate adverse effects

A

Bradycardia, hypotension

Pharm block 4 hemostasis and cardiac (12 decks)

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