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Pharm Exam 2 > Topic 13 > Flashcards

Topic 13 Flashcards

1
Q

Anticoagulants: Indirect thrombin inhibitors=

A

Warfarin (Coumadin)
Unfractionated heparin
Low-MW heparin (Lovenox)
Fondaparinux (Arixtra)

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2
Q

Anticoagulants: Direct thrombin inhibitors=

A

Lepirudin (Refludon)
Argatroban
Bivalirudin (Angiomax)

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3
Q

Warfarin

A

(Coumadin)

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4
Q

Low-MW heparin

A

(Lovenox)

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5
Q

Fondaparinux

A

(Arixtra)

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6
Q

Lepirudin

A

(Refludon)

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7
Q

Bivalirudin

A

(Angiomax)

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8
Q

Anticoagulants inhibit

A

one or more steps in the clotting cascade that lead to fibrin formation

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9
Q

Anticoagulants do NOT

A

dissolve clots

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10
Q

Heparin is a mix of

A

straight-chain polymers consisting of extremely anionic repeating dissacharide units.

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11
Q

Heparin is one of the most acidic molecules in a critter’s body because so many

A

carboxyl and sulfate groups are attached
(and virtually all critters produce heparin, even ones lacking “traditional blood”, so it’s an ancient molecule
on the evolutionary tree.)

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12
Q

Heparin lives in

A

mast and basophils

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13
Q

Unfractionated heparin (the kind that’s used the most) is a mixture of molecules ranging from

A

5000-30,000 Daltons

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14
Q

heparin is measured in

A

units (not by weight)

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15
Q

What’s One (1) Unit of Heparin?

A

“The quantity of heparin required to keep 1 milliliter of blood fluid for 24 hours at 0°C”

This is ~~0.002 mg of heparin/unit

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16
Q

Two Main Sources of Heparin

A
  1. Insteninal
  2. Lung
    - Porcine intestinal -derived heparin may be better in preventing some complications (such as heparin-induced thrombocytopenia)
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17
Q

Heparin is always given

A

parenterally

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18
Q

“Fractionated heparin” = “Low molecular weight heparin” (LMWH): how many daltons?

A

5500

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19
Q

LMWH is much more….

A

uniform, contains less “contaminants” and inactive forms of heparin

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20
Q

Heparin performs a lot of poorly-described functions in critters, but isn’t really

A

an anticoagulant all by itself.

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21
Q

Heparin + AT-III =

A

> 1000X more active anticoagulant activity than AT-III by itself

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22
Q

Interaction of antithrombin with heparin and LMWH is mediated by a

A

pentasaccharide sequence

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23
Q

Unfractionated heparin accelerates interaction of

A

antithrombin with both thrombin and factor Xa

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24
Q

LMWH selectively accelerates interaction of

A

antithrombin and Factor Xa

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25
Q

IV half life: Heparin and LMWH

A

Heparin: 2 hours
LMWH: 4 hours

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26
Q

Anticoagulant response: Heparin and LMWH

A

Heparin: Variable
LMWH: Predictable

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27
Q

Bioavailability:Heparin and LMWH

A

Heparin: 20%
LMWH: 90%

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28
Q

Major adverse effect: Heparin and LMWH

A

Heparin: Frequent bleeding
LMWH: Less frequent bleeding

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29
Q

Setting for therapy:Heparin and LMWH

A

Heparin: Hospital
LMWH: Hospital and out patient

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30
Q

Heparin time to effect

A

Intravenous (IV): a few minutes

Subcutaneous (SQ): 1-2 hours

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31
Q

Heparin is cleared by

A

binding to macrophages and being depolymerized and

desulfonated in the liver…and the metabolites are excreted in the urine

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32
Q

heparin’s half-life is prolonged by either

A

renal &/or liver dysfunction.

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33
Q

Unfractionated heparin’s half-life is

A

~1-2 hours

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34
Q

Fractionated (LMWH) has a much longer half-life

A

3-7 hours

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35
Q

Lower doses of heparin are cleared at a

A

faster rate than higher doses

implying that the process is saturable

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36
Q

Since it’s a metabolic process, heparin clearance is (naturally) slower

A

at lower temps and accelerated at higher temps

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37
Q

Heparin is chemically reversed with

A

Protamine

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38
Q

Heparin side effects

A

Excessive bleeding

Heparin-Induced Thrombocytopenia (HIT) I & II

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39
Q

A synthetic LMWH (a pentasaccharide) (name the drug)

A

Fondaparinux

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40
Q

Fondaparinux: half life? Eliminated how?

A

~20 hours and eliminated unchanged in the urine

41
Q

Fondaparinux major advantage

A

is the elimination of the risk of “bad” (Type II) HIT.

42
Q

Warfarin is a widely prescribed

A

orally administered anticoagulant

43
Q

Warfarin works by inhibiting

A

Vitamin K

44
Q

Other names for vitamin K

A

(phytonadione / Mephyton)

45
Q

Warfarin blocks an enzyme called

A

Vitamin K epoxide reductase

46
Q

Vitamin K epoxide reductase is required to allow the

A

liver to “recycle” spent (oxidized) Vitamin K so eventually stores of Vitamin K are simply depleted.

47
Q

Warfarin is NOT a Vitamin K

A

antagonist
(it doesn’t have antagonist kinetics)
…so giving the critter Vitamin K readily reverses the effects of warfarin.

48
Q

Liver requires Vitamin K to produce what factors

A 
II: Prothrombin
VII: Proconvertin
IX: Plasm Thromboplastin Component
X: Stuart-Power Factor 
 2 7 9 10
49
Q

Warfarin Blocks the γ-carboxylation sites of factors II, VII, IX, & X as well as

A

Proteins C and S

–Consequently, the liver produces incomplete, biologically inactive molecules instead of functioning clotting factors

50
Q

Proteins C and S are also anticoagulants via their

ability to block factors

A

Va and VIIIa

51
Q

Takes a while for Warfarin to exert its clinical

effect (____ hours) since those Vitamin K stores have to be depleted

A

8-24 hours

52
Q

Warfarin peak effects occur

A

~2-4 days (once those stores are completely empty).

53
Q

Warfarin’s half-life and duration of action are insanely variable because

A
  1. it’s highly protein-bound

2. Drugs, genetics, foods, spices (!), etc. all effect how long it lasts

54
Q

Warfarins normal half life is

A

~ 40 hours

55
Q

Warfarin Side Effects

A

Bleeding
Birth/fetal deformities &/or death.
Warfarin necrosis

56
Q

Warfarin dose

A

5-7mg/day with adjustments made after ∽ one week

57
Q

Warfarin typically monitored via the ______. Normal time? Normal value?

A

prothrombin time (PT)
Typically this is 12-13 seconds
“normal” PTs is 12.5 seconds

58
Q

PT measures the activity of which factors

A

VII, X, V, II, I (7, 10, 5, 2, 1)

59
Q

What is added to the critter’s plasma before an optical measurement is made of the subsequent clot formation

A 
Tissue Factor (Factor III) 
Calcium (Factor IV)
60
Q

INR stands for

A

“International Normalized Ratio”

61
Q

INR= [formula]

A

Critters PT / Labs normal PT mean

62
Q

Direct Thrombin Inhibitors All bind directly to

A

thrombin

63
Q

Direct Thrombin Inhibitors Vary in their

A

affinities for thrombin, half-lives, and how they are cleared from the body.

64
Q

What Irreversibly binds to and deactivates thrombin, Contains many contaminants and is hard to produce

A

Hirudin

65
Q

What is a synthetic, purified form of hirudin that Bivalently and irreversibly binds to thrombin

A

Lepirudin (Refludan)

66
Q

Lepirudin

A

(Refludan)

67
Q

Unlike heparin, lepirudin is not

A

dependent on interactions with AT III for its function

68
Q

One molecule of lepirudin binds to

A

one molecule of thrombin

69
Q

how is Lepirudin given

A

parenterally

70
Q

Lepirudin is Cleared by the

A

kidneys

71
Q

Lepirudin half life

A

1 hour, but can increase to several days in renal insufficiency/failure patients!

72
Q

what drug is Very antigenic

A

Lepirudin

73
Q

~50% of patients who receive Refludan courses of therapy develop

A

antibodies to the lepirudin-thrombin complex

74
Q

the lepirudin-thrombin complex prevent Lepirudin’s

A

clearance by the kidneys and increases its anticoagulant effect &/or can cause an anaphylactic reaction.

75
Q

Critters on Lepirudin must there have BOTH their ___ and ___ monitored.

A

aPTTs and renal functions

76
Q

Lepirudin is used as a therapy for HIT and/or as an

A

alternative anticoagulant (in place of heparin)in patients with HIT

77
Q

Lepirudin: Unlike heparin, NO …

A

REVERSAL AGENT EXISTS!!!

78
Q

What is a completely synthetic yet chemically smaller

“cousin” of hirudin

A

Bivalirudin (Angiomax)

79
Q

Bivalirudin

A

(Angiomax)

80
Q

Bivalirudin Like hirudin, it’s also a

A
  • bivalent direct thrombin inhibitor
  • operates independent of AT III
  • Is given parenterally
81
Q

Bivalirudin Less renal clearance (___%) than lepirudin (the remainder being metabolized)

A

~20%

82
Q 
Bivalirudin half life
Normal?
Mod. renal dysfunction?
Severe renal dysfunction?
Dialysis patient?
A

Normal= 20-25 minutes
Mod. renal dysfunction= 35 minutes
Severe renal dysfunction= 1 hour
Dialysis patient= 3.5 hours

83
Q

Bivalirudin Can be removed by

A

hemoconcentrators

84
Q

Bivalirudin: Very commonly used during

A
  • -PTCAs to prevent platelet activation

- -anticoagulation for patients with HIT

85
Q

Bivalirudin Monitoring:

  • Ideally , anticoagulation (as on bypass) is measured with the ______.
  • Practically monitored with _____.
A 
Ideally= “ecarin clotting time” (ECT)
Practically= ACT’s
86
Q

what is a parenterally-administered small molecule direct thrombin inhibitor.

A

Argatroban

87
Q

Argatroban half life

A

~40-50 minutes

88
Q

Argatroban: Clinical use similar to Angiomax but monitored with

A

aPTTs

89
Q

Argatroban is eliminated by

A

hepatic clearance

90
Q

Angiomax vs. Argatroban

•Essentially, the choice is made by whether the patient has

A

intact renal or hepatic function

…and ease of monitoring the anticoagulation

91
Q

Oral Anticoagulants: drug names

A 
Dabigatran etexilate (Pradaxa)
Apixiban (Eliquis) 
Rivaroxaban (Xarelto)
92
Q

Dabigatran etexilate

A

(Pradaxa)

93
Q

Apixiban

A

(Eliquis)

94
Q

Rivaroxaban

A

(Xarelto)

95
Q

Dabigatran etexilate (Pradaxa) =

A

An oral anticoagulant cleared by the kidneys that also acts as a direct thrombin inhibitor

96
Q

what drug is a possible future replacement for oral warfarin (don’t need to test INRs, fewer drug interactions, less variable half-life)

A

Dabigatran etexilate (Pradaxa)

97
Q

Dabigatran etexilate (Pradaxa) is currently used for

A

A-Fib

98
Q

Apixiban (Eliquis) and Rivaroxaban (Xarelto) are both…

A

oral anticoagulants that directly inhibit Factor Xa

–Both are cleared renally and used for a-fib

Pharm Exam 2 (9 decks)

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