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Drugs for Coagulation disorders

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Title: Drugs for Coagulation disorders


1
Drugs for Coagulation disorders
2
  • There are a number of different categories of
    drugs which modify the coagulation process
  • I. Anticoagulants
  • II. Antiplatelet agents
  • III. Thrombolytics

3
I. AnticoagulantsA. The coagulation cascade
  • The coagulation cascade begins when injured cells
    release thromboplastin.

4
  • Thromboplastin converts the clotting factor
    prothrombin to thrombin.

5
  • Thrombin then converts the plasma protein
    fibrinogen to long strands of fibrin and
    activates several clotting factors (V, VIII,
    XIII, and protein C)

6
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7
  • The fibrin strands form an insoluble web

8

9
B. Types of anticoagulants
  • The mechanism of action of anticoagulant
    medications involves either the inactivation of
    various existing coagulation factors, or

10
  • preventing the synthesis of coagulation factors
    (the vitamin K antagonists)

11
  • Anticoagulant medications do NOT dissolve clots.

12
1. heparins
  • a. standard heparin
  • b. low molecular weight (LMW) heparins

13
  • Heparins are indicated for the treatment of
  • deep vein thrombosis (DVT)
  • prophylaxis and treatment of venous thrombi,
    alone
  • prophylaxis and treatment of venous thrombi in
    conjunction with pulmonary emboli

14
  • Heparins are NOT direct thrombin inhibitors.

15
  • Instead, heparins prevent thrombin formation by
    binding to clotting factors in the circulation.

16
  • These clotting factors then bind to and
    inactivate thrombin, the major enzyme in the
    clotting pathway.

17
  • The main commercial sources of standard heparin
    are the lungs and intestines of cattle (bovine)
    and pigs (porcine).

18
  • LMW heparins are derived from porcine heparin.

19
  • They are smaller in size as they only contain the
    anticoagulant fraction of heparin, and not the
    additional saccharide chains that standard
    heparin has.

20
a. Standard heparin
  • Standard heparin has an immediate onset of action
    if administered IV, it peaks within 5-10 minutes,
    and its duration is 2-6 hours.

21
  • Standard heparin has an onset of action of 20
    minute 1 hour if administered SC, it peaks
    within 2 hours, and its duration is 8-12 hours.

22
  • Standard heparin IV administration bolus of
    10,000 12,000 units followed by 5,000-10,000
    units every 4-6 hours

23
  • Standard heparin SC administration bolus of
    10,000 12,000 units followed by 15,000-20,000
    units every 12 hours

24
b. Low molecular weight (LMW) heparins
  • LMW heparins are ONLY administered SC, have a
    rapid onset of action, generally peak within 3-6
    hours, and have a duration of 12-24 hours
    depending on the agent. Specific LMW heparins
    include

25
  • i. dalteparin (Fragmin)
  • Indicated for prophylaxis of Deep Vein Thrombosis
    (DVT) in patients undergoing abdominal surgery or
    hip replacement surgery.

26
  • ii. enoxaprin (Lovenox)
  • Indicated for prophylaxis of DVT in patients
    undergoing abdominal, hip, or knee surgery.

27
  • iii. fondaparinux (Arixtra)
  • Indicated for both the treatment of and
    prophylaxis of DVT and pulmonary embolism (PE).

28
  • iv. tinzaparin (Innohep)
  • Indicated for both the treatment of and
    prophylaxis of DVT.

29
  • LMW heparins have certain advantages over
    standard heparin
  • 90 bioavailability (standard heparin has 30)

30
  • LMW heparin can be dosed based on body size
    without coagulation test monitoring (if patient
    has normal kidney function)

31
  • Adverse effects of heparins
  • hemorrhage
  • anemia in elderly with Lovenox, due to decreased
    clearance
  • fever
  • hair loss
  • thrombocytopenia (? in no. of platelets)

32
  • Black box warning for LMW heparin use in patients
    concurrently receiving epidural or spinal
    anesthesia as it increases the risk for epidural
    or spinal hematomas

33
2. thrombin inhibitors
  • Unlike the heparins, these drugs bind directly
    to thrombin. They are all administered IV.

34
  • a. argatroban (Argatroban)
  • indicated for patients with, or at risk for
    thrombocytopenia who are undergoing percutaneous
    coronary intervention (PCI).

35
  • b. bivalirudin (Angiomax) used, along with
    aspirin, in patients with unstable angina who
    undergo PCI. This treatment is intended to reduce
    the risk of acute ischemic complications

36
  • c. lepirudin (Refludan) derives from the natural
    product hirudin, found in leech saliva.

37
  • Leeches have been used for bloodletting since the
    times of the ancient Greeks.

38
3. anticoagulants which prevent the synthesis of
coagulation factors
  • This category of anticoagulant is significantly
    different from the heparins in that it can be
    administered orally.

39
  • This type of anticoagulant has a longer onset
    because of the time required to clear the normal
    clotting factors from the circulation before an
    effect can be observed.

40
  • The only drug in this class is warfarin sodium
    (Coumadin) 2-10 mg

41
  • Its onset of activity is about 12-72 hours.

42
  • However, its duration of action is longer (2 to
    10 days) even after drug administration has been
    discontinued.

43
  • Coumadin is indicated for the treatment of DVT
    and prevention of myocardial re-infarction

44
  • Adverse effects include
  • GI disturbances
  • hypotension
  • hair loss
  • headache
  • hemorrhage (most serious)

45
  • A black box warning indicates that there is an ?
    risk of hemorrhage in
  • patients over 65
  • patients with a history of GI bleeding
  • INR gt 4

46
  • INR (international normalized ratio) is a test
    used to monitor coagulation status.

47
  • People not on anticoagulants have an INR of 1
  • An INR of 2 3 is needed for a therapeutic
    effect with warfarin

48
II. Antiplatelet agents
  • Antiplatelet agents exert an anticoagulant effect
    by interfering with various aspects of platelet
    function.

49
  • Antiplatelet agents are indicated for the
    treatment of
  • thrombocytopenia
  • acute coronary syndrome
  • prevention of myocardial re-infarction
  • and reducing coronary events

50
  • The 2 subclasses of antiplatelet agents are
  • A. nonselective COX inhibitors
  • B. adenosine diphosphate (ADP) receptor blockers

51
A. nonselective COX inhibitors
  • Normally, the cyclooxygenase enzyme pathway in
    platelets results in the production of
    thromboxane A2, a potent platelet aggregator.

52
  • Aspirin, in doses from 81 mg (baby aspirin) to
    325 mg (adult analgesic dose) irreversibly blocks
    a step in this pathway, preventing the synthesis
    of thromboxane A2.

53
  • Therefore, thromboxane will not be active until
    new platelets are formed.

54
B. ADP receptor blockers
  • These drugs interfere with a receptor on the
    membrane of platelets, preventing them from
    aggregating.

55
  • Adenosine diphosphate (ADP) normally binds to
    these membrane receptors in platelets, resulting
    in the coagulation of the platelets.

56
  • The drugs in this class block the receptor so
    that ADP cannot bind.

57
  • All of the drugs in this class are administered
    orally.

58
  • 1. ticlopidine (Ticlid) 250 mg, bid
  • 2. clopidogrel (Plavix) 75 mg
  • 3. cilostazol (Pletal) 100 mg, bid
  • 4. prasugrel (Effient) 5 10 mg with food
  • 5. anagrelide (Agrylin) 1.0 mg, bid

59
III. Thrombolytics
  • Thrombolytics are enzymes used to dissolve blood
    clots.

60
  • They convert plasminogen to plasmin, which is
    then able to degrade the fibrin present in clots.

61
  • Their primary functions are to break apart
    pulmonary emboli and coronary artery thromboses
    during acute MI.

62
  • They need to be administered as soon as possible
    once it has been established that a clot or
    infarct has occurred.

63
  • Other disorders for which they may be indicated
    are
  • DVT
  • stroke
  • occluded central venous access devices

64
  • For the treatment of acute MI administer the
    drug within 1-6 hours of the onset of symptoms.

65
  • There is a longer window of opportunity for use
    of these drugs in treating a pulmonary embolism.
    Here the time for initiation of therapy may be up
    to a few days.

66
  • All drugs in this class are enzymes that must be
    administered IV.

67
A. streptokinase
  • Streptokinase (Streptase, Kabbikinase)
    generally, 250,000 IU over 30 minutes, then
    100,000 IU/hour for up to 72 hours
  • Larger doses may be used in the treatment of MI

68
B. urokinase
  • urokinase (Abbokinase) IV 4400-6000 IU
    administered over several minutes to 12 hours

69
  • A symptomatic ulnar artery occlusion before and
    after urokinase infusion therapy.

70
C. thrombolytics produced via recombinant DNA
  • alteplase (Activase, Cathflo), reteplase
    (Retavase) and tenecteplase (TNKase) are
    thrombolytic enzymes produced through recombinant
    DNA technology

71
  • alteplase based on patient weight, not to exceed
    100 mg. Generally, a 15 mg bolus, followed by 50
    mg over next 30 minutes then 35 mg over the next
    60 minutes

72
  • reteplase 10 unit bolus over 2 minutes, wait 30
    minutes, repeat

73
  • tenecteplase a single bolus, over 5 seconds
    based on body weight, not to exceed 50 mg
  • Generally used in conjunction with aspirin and
    heparin therapy

74
  • Adverse effects of the thrombolytics
  • hemorrhage
  • rash/itching
  • headache
  • nausea
  • bronchospasm
  • cardiogenic shock or arrhythmias with the
    recombinants
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