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Pharmacology > Anticoagulants and Antiplatelets > Flashcards

Anticoagulants and Antiplatelets Flashcards

1
Q

What is hemostasis?

A

Process that stops bleeding

  • Formation of a platelet plug
  • Production of fibrin
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2
Q

What does the clotting cascade create? What are the 2 pathways?

A

Results in fibrin - a clot forming substance

Coagulation cascade is divided into intrinsic and extrinsic pathways

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3
Q

When should anticoagulants be used? How do they function?

A

Used prophylactically to prevent clot formation (thrombus) or an embolus (dislodged clot). Works on different points of cascade depending on drug

Does not impact existing blood clots

Should be used in cases of:

  • MI
  • Unstable angina
  • Atrial fibrillation
  • DVT eg. major orthopedic surgery
  • Indwelling devices (mechanical heart valves)
  • Pulmonary embolism
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4
Q

What 4 drugs prevent clot formation?

A
  1. Heparin
  2. Low-molecular-weight heparins (LMWH)
  3. Warfarin - oral
  4. Direct Factor X and Thrombin inhibitors
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5
Q

When should anticoagulants not be used?

A
  • Drug allergy
  • Acute bleeding process
  • Thrombocytopenia
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6
Q

Which anticoagulant drug is contraindicated in pregnancy?

A

Warfarin

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7
Q

What are the adverse effects (5) of anticoagulants?

A

Bleeding risk increases with increased dosages

  1. Gums bleed
  2. Nosebleeds
  3. Unusual bruising
  4. Anemia/low Hct (hematocrit)
  5. Tarry stool
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8
Q

How does Heparin impact the clotting cascade?

A

Indirectly affects Thrombin II, Factor Xa, and other factors in the *intrinsic pathway

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9
Q

What is a common issue with Heparin dosing?

A

It’s very unpredictable (due to varying lengths of molecules)

  • It’s monitored by activated partial thromboplastin times (aPTT)
  • Measures the intrinsic pathways
  • aPTTs need to be 1.5-2.5 greater than control
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10
Q

How is Heparin given, and what are some of its characteristics?

A

Given IV or SC

Effective within minutes

Short half life (1-2 hours)

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11
Q

When should Heparin use be stopped? What’s the antidote?

A

When Heparin-induced thrombocytopenia (HIT) occurs

  • 1-5% of population
  • Stop heparin administration and use alternatives

Hypersensitivity reactions
- Urticaria, fever, chills

Protamine sulfate - antidote

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12
Q

What is an example of LMWH and how is it different from Heparin?

A

*Enoxaparin

More predictable anticoagulant response
Does not require frequent laboratory monitoring
- Often given at home
Given SC
- Indirectly inhibits Factor X only
- Less thrombocytopenia than heparin
- Protamine sulphate - same antidotes
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13
Q

What are 2 alternatives to Heparin

A
  1. Danaparoid
    - SC or IV
    - Structurally distinct from heparin
  2. Fondaparinux
    - Synthetic
    - SC or IV
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14
Q

What are some client implications for Heparin and LMWHs?

A

Heparin:
Double check dosages with another RN
SC doses must be SC not IM
Preferred site is abdomen

LMWH:
SC in abdomen only
Rotate sites around lower abdomen below umbilicus

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15
Q

How does Warfarin work?

A
  • Very similar to coumarin.
  • Vitamin K antagonist.
  • Vitamin K is essential for production of several clotting factors (VII, IX, X, prothrombin)
  • Max effect may take 3-5 days
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16
Q

How is Warfarin monitored?

A

Through a clotting lab test (prothrombin time (PT))
- Needs to be 1.3-1.5 times the normal level to be therapeutic

INR (international normalization reference ratio)

  • Corrects for lab-to-lab variability in testing
  • Normal target INR range needs to be 2-3 x control
  • The highest therapeutic range needs to be at 2.5-3.0. Normal is 0.8-1.2

These both measure activity of extrinsic pathway

17
Q

What happens to warfarin effectiveness when too much or too little vitamin K in diet?

A

Vitamin K decreases the effect of warfarin because it’s a key part in the clotting cascade.

Too much vitamin K = lowered effect of Warfarin

Too little vitamin K = increased effect of Warfarin

18
Q

Patient teaching on Warfarin

A

Keep intake of vitamin K constant (tomatoes, dark leafy green vegetables)

Be careful in taking other meds or natural products (drug-drug interactions

19
Q

What are 2 examples of Direct-Acting Oral Anticoagulants (DOACs), and what’re the advantages?

A 
Dabigatran
Direct thrombin inhibitor
- Rapid onset
- Fixed doses
- No blood test
- Few drug-drug interactions
- No dietary concerns
- Lower risk of bleeds

Rivaroxaban
Direct Factor Xa Inhibitor
Similar advantages as dabigatran

20
Q

What’re the adverse effects for all anticoagulants?

A

Increased bleeding (mild-life threatening)

21
Q

Patient education on all anticoagulants?

A

Importance of regular lab testing, signs of abnormal bleeding (bleeding gums, unexplained nosebleeds, bruising, heavier menstrual bleeding, bloody or tarry stools, vomiting blood, bloody urine or sputum, abdominal pain)

22
Q

What is the function of Antiplatelet agents, and what are 2 examples?

A

To prevent platelet activation by inhibiting cyclooxyrgenase pathway

Acetylsalicylic acid causes the irreversible inhibition of COX in platelets

Clopidogrel (Plavix) is a irreversible ADP receptor blocker

23
Q

When should you use antiplatelet agents?

A

To prevent clots and reduce risk of fatal and nonfatal strokes

24
Q

What are the benefits and consequences of combining ASA and clopidogrel?

A

Produces additive antiplatelet activity, but increases bleeding potential

25
Q

What is the function of thrombolytic agents and what’s a newer agent?

A

Break down preformed clots

Recombinant tissue plasminogen activator (tPA)
- Alteplase

26
Q

How do thrombolytic agents work?

A

Activates fibrinolytic system to break down clots in blood vessels

Re-establishes blood flow to hear muscle via coronary arteries (MI), and to brain after strokes

27
Q

When should we use Thrombolytic agents?

A

Acute MI, arterial thrombolysis, DVT, occlusion of shunts or catheters, pulmonary embolism.

28
Q

What are are the two major adverse effects of thrombolytic agents?

A

Bleeding (internal, intracranial, superficial)
Dysrhythmias

Other effects: nausea, vomiting, hypotension, anaphylactoid reactions

29
Q

What function do antifibrinolytic agents have?

A

Prevents the breakdown of fibrin in existing clots, and promote clot formation/maintenance

30
Q

What is an example of an antifibrinolytic agent and how does it work?

A

Aminocaproic acid

Inhibits fibrinolysis
Acts as an antidote to thrombolytic agents (eg. alteplase)

Used to treat excessive bleeding, hyperfibrinolysis, surgical complications, excessive oozing from surgical sites, and decrease total blood loss in postoperative period

31
Q

Contraindications for antifibrinolytic agents?

A

Allergy and in patients with DIC (disseminated intravascular coagulation)

Pharmacology (29 decks)

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