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Pharm '14 test 2 > Anticoagulants > Flashcards

Anticoagulants Flashcards

1
Q

The three basic mechanisms of hemostasis are

A

Vasoconstriction, platelets, and clotting factors

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2
Q

Basic steps in hemostasis

A

1) Vasoconstriction
2) Formation of platelet plug
3) Activation of clotting cascade
4) Formation of fibrin blood clot
5) Clot retraction and dissolution

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3
Q

Primary hemostasis

A

Occurs immediately

Results in platelet plug

Exposed subendothelial collagen attracts platelets which start to adhere to each other

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4
Q

Factors involved in primary hemostais (also causes local vasoconstriction)

A

vWF
CF VIII
ADP

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5
Q

Adhered platelets release ________ and use _____ and _____ as a connecting agent

A

TXA2

Fibrinogen and vWF

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6
Q

Platelet degranulation agents

A

5-HT, Histamine- vasoconstrictors

Thromboxane- vasoconstriction/degranulation

ADP- promotes adherence and degranulation

CF Va, VIIIa, IXa

Platelet factor 4 (heparin neutralizing factor)

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7
Q

Secondary hemostasis takes place over what kind of time frame?

A

Minutes to hours

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8
Q

What is the end product of the coag cascade in secondary hemostasis?

A

FIBRIN

This forms the meshwork of protein that helps to stabilize the platelet plug and trap other cells

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9
Q

Basic intrinsic pathway (PTT)

A

Factor XIIa–> Xa–>Prothrombin–> Thrombin

Fibrinogen–> Fibrin

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10
Q

Basic extrinsic pathway (PT)

A

Tissue factor and Factor VIIa–> Xa–>
Prothrombin–> Thrombin
Fibrinogen–> Fibrin

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11
Q

Natural anticoagulants

A 
PCI2
Antithrombin III
Heparin
Protein C
Protein S
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12
Q

After a clot forms and stabilizes, it then

A

Retracts

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13
Q

How does clot retraction work?

A

Platelets trapped in the fibrin mess contain actinomyosin-like contractile proteins, which squeeze out protein-free serum. This mostly takes place within the first hour.

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14
Q

Describe the fibrinolytic system

A

Mediated by plasmin,which becomes activated by coagulation and inflammation substances

Plasmin splits fibrin and fibrinogen into fibrin degradation products

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15
Q

Antiplatelet aggregation agents

5 oral

3 IV

A

Oral agents- aspirin, ticlopidine, clopidogrel, prasugrel, ticagrelor

IV- abciximab, eptifibatide, tirofiban

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16
Q

What does aspirin inhibit? What type of inhibition is it?

A

COX inhibitor

Irreversible! Remember platelets are around for about 10 days.

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17
Q

Aspirin is indicated for

A

Prevention of recurrent ischemic events, such as stroke, MI, and symptomatic PVD

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18
Q

ASA dose

A

81-325mg qday

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19
Q

ASA precautions

A

Children (Reye’s syndrome)
Pregnancy
CV- blocks ACE, BB, and diuretic effects d/t prostaglandin inhibition
Asthmatics- results in increased leukotriene production
Increased bleeding with other anticoags

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20
Q

Treatment for over anti-coagulation with ASA?

A

Platelet transfusion, otherwise you gotta wait a long time

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21
Q

How does ticlopidine (ticlid) work?

A

Blocks APD receptor on platelets and inhibits fibrinogen binding

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22
Q

When is ticlopidine used?

A

Same indications as ASA, usually used for ASA intolerance

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23
Q

Ticlopidine is bad news bears because…

A

It causes extreme neutropenia, thrombotic thrombocytopenic purpura, GI upset (really..?), and its also teratogenic

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24
Q

Clopidogrel (Plavix) works by

A

Irreversibly blocking ADP receptor on platelet and inhibits fibrinogen binding

Used for same stuff as ASA, usually as dual therapy with ASA (more effective, also more bleeding)

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25
Clopidogrel dosing
Loading dose of 300mg or 600mg Daily dose of 75mg
26
Clopidogrel precautions
Metabolized by CYP2C19, may need increased dosing due to genetic variation Inhibits CYP450 Severe renal/hepatic disease, reduce dose
27
For alllllll of these drugs using more than one will...
Increase your risk of bleeding
28
Clopidogrel pts most at risk of bleeding?
Elderly, underweight, previous TIA/stroke
29
Bleeding treatment on clopidogrel
Stop drug GIve platelets
30
Prasugrel (Effient) what is it? When might a pt be on it?
New thienopyridine, better risk reduction than clopidogrel, but also causes more fatal bleeding events Often used in clopidogrel non-responders
31
Prasugrel dosing and precautions
10mg qday Active bleeding Previous stroke/tia, underweight, >75- consider 5mg qday Risk of bleeding during CV surg is 4x greater than clopidogrel. Don't use pre-cath.
32
Ticagrelor (Brilinta) works by ______? How does it compare to clopidogrel?
Blocks ADP receptors by allosteric antagonism Better than clopidogrel for mortality reduction post MI/stroke, but also more bleeding and much higher rate of fatal ICH
33
Ticagrelor uses and dosing
Prevention of recurrent ischemic events after stroke, ACS, and post PCI 180mg once, 90mg bid thereafter Always as dual therapy with ASA unless contraindicated
34
Ticagrelor precautions
ASA more than 100mg aday Hepatic dysfunction Hold for >5 days pre-surg BID dosing Contraindications- active bleeding, ICH history
35
How do GPIIb/IIIa inhibitors work? Uses? 3 drugs-
Block GPIIb/IIIa receptor, which prevents fibrinogen binding Used for ACS and PCI Abciximab (ReoPro), Eptifibatide (Integrilin), Tirofiban (Agrastat)
36
Abciximab (ReoPro) is used for _______? When used with heparin what's the aPTT goal? Downsides?
Used in ACS with planned PCI aPPT goal of 60-85 sec Most expensive in its class and most prolonged effects
37
Eptifibatide uses and dosing considerations
Used for ACS and PCI Dosing based on serum creatinine <2.0 mg/dl- 2.0 mcg/kg/min for up to 72 hours 2.0-4.0 mg/dl- 1.0mcg/kg/min for up to 72 hours
38
GPIIb/IIIa inhibitors- How do you treat bleeding?
Abciximab (ReoPro)- reverse with platelets Eptifibatide (Integrilin) and Tirofiban- turn it off and wait
39
Temporary interruption of anti-platelet therapy should take place _______ prior to surgery
7-10 days
40
Anti-platelet therapy should resume ________ post-op as long as hemostasis is achieved
within 24 hours or next AM
41
For pts at high risk of CV events, when should ASA/Clopidogrel be stopped?
ASA should NOT be discontinued Clopidogrel should be stopped at least 5 days prior to surg
42
How does heparin work and what is it used for?
Activates antithrombin III--> increases inhibition of thrombin IIa and Factor Xa 1000 fold Used for DVT prophylaxis/treatment, PE treatment, ACS, when warfarin is started or contraindicated
43
Heparin dosing for DVT prophylaxis
5000 units SubQ q8hrs (q12hr dosing sometimes...for NeuroSurg, ESRD)
44
IV infusion heparin dosing
Weight-based bolus Weight-based infusion Protocol adjusted by aPTT or anti-Xa values (q6hrs until stable, then qday)
45
Drawbacks of heparin
Variable effect, frequent titration DOES NOT inhibit clot-bound thrombin
46
Heparin reversal agent
Protamin 1mg/100u of heparin
47
Incidence of HIT
1% @ 7 days | 3% @ 14 days
48
HIT type I
Non-immune mediated, BENIGN Mild drop in platelets, <4 days, not progressive nor associated with thrombosis
49
HIT type II
Immune mediated, more typical onset and MORE BAD Always follows heparin exposure (check history) Reduction in platelets to <150,000 OR 50% reduction from PRE-HEPARIN exposure Typically 7-14 after initial exposure, but may be much shorter if pt was exposed in the past
50
Thrombocytopenia occurs what percent of the time with heparin therapy? More common in UF or LMWH?
about 2-5 More common in UF heparin
51
Typical pt/platelet count/onset time for thrombocytopenia
Surg>med>OB 38,000-60,000 Typical onset (66%)- exposure of 5-14 days Delayed (3-5%)- exposure of 2-6 weeks Rapid (25-30%) hours-days (usually has history of heparin exposure and circulating antibodies from previous 100 days)
52
HITT (HIT with thromboembolism) % of cases Venous vs Arterial Mortality rate and amputation rate
10-25% of cases Venous (4x more common)- DVT, PE, venous limb gangrene, dural sinus thrombosis Arterial- CVA, limb ischemia, skin necrosis, MI, gut ischemia, adrenal/renal/spinal artery infarcts 25-30% mortality, 25% amputation rate
53
HIT lab tests
ELISA - measures titer of IgG to heparin-PF4 complex - simple and readily available - 90% sensitive, 80% specific SRA - detects platelet activation - labor intensive, usually a send-out lab
54
Management of HIT
Stop all pro-thrombocytopenic drugs STOP heparin (FOREVER) and START non-heparin anti-coag (usually Argatroban) Check history for heparin exposure Remove all sources of heparin (flushes, coated devices, sq DVT prophylaxis)
55
LMWH (Enoxaparin) MOA and uses
~5,000 daltons in size Binds antithrombin III and inhibits factor Xa Used for DVT prophylaxis, ACS, and VTE treatment
56
How can the effects of LMWH be checked?
Anti-Xa levels, but this is not routinely done
57
In what pt population on LMWH therapy would you want to monitor anti-Xa levels
Pregnant women
58
Precautions with LMWH
Use weight based dosing for obese pts Not recommended in severe renal insufficiency, decrease dose by 50% if no alternative Contraindicated in spine surg and patients with epidural catheters
59
Can protamine reverse LMWH?
Yes, but only ~60% reversal
60
How does Fondaparinux (Arixtra) work? What is it used for?
It is a synthetic factor Xa inhibitor. Binds with anti-thrombin III to potentiate Xa inhibition (300x). No effect on IIa (thrombin). Used in ACS, PE/DVT prophylaxis, DVT treatment
61
Fondaparinux dosing, contraindications, reversal
7.5mg subq qday for prophylaxis, 10mg for VTE or wt >100kg Contraindicated for CrCl< 30 ml/min, spinal puncture/anesthesia No known reversal, FFP ineffective. Discontinue drug and provide supportive care.
62
Direct thrombin (IIa) inhibitors
Hirudin, lepirudin, desirudin, hirulog, argatroban (reversible), bivalirudin Used in HIT (argatroban, lepirudin) PCI (Bivalirudin)
63
Toxicities, interactions, and bleeding treatment for direct thrombin inhibitors
Bleeding Lepirudin and Desirudin can only be used once on a patient d/t anaphylaxis risk Increased bleeding with other anti-coagulants Stop infusion, may respond to factor VII, FFP, and cryoprecipitate
64
What does warfarin interfere with?
Production of vitamin K dependent clotting factors (II, VII, IX, X) and carboxylation of natural anticoagulants protein C and protein S
65
What is warfarin used for?
DVT, a-fib, mechanical heart valve thrombosis prevention Long-term VTE treatment
66
The INR goal for most warfarin indications is
2. 0-3.0 | 2. 5-3.0 in high risk pts
67
For uncomplicated DVT/PE what is the normal duration of warfarin therapy?
3 months
68
When transitioning to warfarin, how long should heparin or LMWH overlap for?
1-2 days
69
What genetic variants can require changes in warfarin dosing?
Variations in CYP2C9 can decrease warfarin metabolism Variations in vitamin k expoxide reductase can require dose reductions
70
Warfarin toxicities
Bleeding, birth defects, cutaneous necrosis
71
Warfarin interactions
``` Increased effect- Amiodarone CImetidine Acetaminophen Phenylbutazone ``` ``` Decreased effect- Sucralfate Cholestyramine Spironolactone Barbiturates Vitamin k containing foods ```
72
Warfarin reversal
Vitamin K, IV or PO FFP
73
In terms of surgery, when should warfarin be stopped and restarted?
5 days prior to OR Restarted 12-24 hours post-op if normal hemostasis has been achieved High risk patients can be bridged with heparin up to 4-6hrs pre-op
74
What does dabigatran (pradaxa) inhibit? What is it used for?
It is a direct thrombin inhibitor (IIa) Stroke prevention in non-valvular a-fib and VTE prophylaxis after total knee/hip replacement 110mg bid for high bleeding risk or renal impairment , otherwise 150mg bid
75
How does dabigatran to warfarin?
150mg dose is superior for reduction of stroke and systemic embolism with no difference in bleeding. 110mg dose in noninferior for prevention and has a 20% reduction in bleeding risk
76
All of the new oral anticoagulants (dabigatran, rivaroxaban, and apixaban) have what disadvantages?
High cost (bid dosing for apixaban), no antidote, no assay for monitoring, and no long term data.
77
Rivaroxaban (Xarelto) MOA, uses, and dosing
Direct factor Xa inhibitor Used for stroke and systemic embolism prevention in a-fib 20mg qday
78
How does rivaroxaban compare to warfarin?
noninferior, similar bleeding risk, but decreased risk of ICH and fatal bleeding
79
Advantages of dabigatran
No routine monitoring needed Less influenced by diet and other drugs Rapid time to peak action (1 hr) Short half like (12-14 hrs) in pts with normal renal function
80
Apixaban (Eliquis) MOA, uses, dosing
Direct Xa inhibitor Used for stroke and systemic embolism prevention in a-fib 5mg bid
81
How does apixaban compare to other anti-coags
Clear benefit over ASA for patients unable to take warfarin Superior to warfarin for prevention and reduced risk of bleeding, in particular lower rates of ICH and mortality
82
Fibrinolytic drugs and how they work
Streptokinase, Urokinase, t-PA, Tenecteplace (TNK-ase) Plasminogen activators convert plasminogen to plasmin--> plasmin causes fibrinolysis
83
Uses for fibrinolytics
Acute ST-elevation MI Acute ischemic stroke (within 6 hours of symptom onset) t-PA only Urokinase only for PE or central line de-clotting
84
tPA dosing vs TNKase dosing
tPA 10 units over 2 min, repeat in 30 minutes TNKase 30-50mg given as a one time bolus over 5 seconds
85
Absolute contraindications for fibrinolytics
Previous hemorrhagic stroke Ischemic stroke in last 3 months or acute within last 3 hours Known intracranial neoplasm Active internal bleeding, excluding menses Suspected aortic dissection SIgnificant closed head or facial trauma within 3 months
86
Relative contraindications for fibrinolytics
BP > 180/110, treating it is ok in terms of removing this contraindication Severe chronic HTN INR>2.5, use of other anticoagulants Known bleeding disorder Non-compressible vascular puncture Recent trauma within 2-4 weeks (traumatic CPR) Major surg <3 weeks Recent internal bleeding or PUD (2-4 weeks) Pregnancy For streptokinase allergy or prior exposure (5 days to 2 years)

Pharm '14 test 2 (5 decks)

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