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Sys. Pharm Week4 > Antiplatalet And Thrombolytic Drugs > Flashcards

Antiplatalet And Thrombolytic Drugs Flashcards

1
Q

Drugs affect thrombosis in three distinct
ways ,

A

• Blood coagulation (fibrin formation)
•Platelet function
• Fibrin removal (fibrinolysis)

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2
Q

ANTIPLATELET DRUGS: ASPIRIN
MoA

A
  • Low-dose aspirin profoundly (> 95%) inhibits platelet TXA2 synthesis
    • Irreversible inhibition of cyclo-oxygenase 1 (COX-1)
  • Oral administration is relatively selective for platelets because of pre-systemic elimination
  • TXA2 synthesis does not recover until the affected cohort of platelets is replaced in 7–10 days (no nucleus)
  • Low dose (75mg once daily) usually recommended for thromboprophylaxis in high risk patients (e.g. post-MI)
  • For acute administration (e.g. thrombotic stroke,
    MI) single dose of 300mg given to achieve rapid
    and extensive inhibition of TxA 2
  • Followed by 75mg daily doses
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3
Q

Aspirin: AE

A
  • GI irritation and bleeding
  • May stimulate attack in asthmatics
  • Reye’s syndrome in children
  • Tinnitus, vertigo, nausea and vomiting – high doses
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4
Q

PURINERGIC RECEPTORS IN PLATELETS

A

‘P2Y1
- Gq-coupled: induces a shape change and
aggregation initiation

P2Y 12
- Couples to Gi
- Further promotes and amplifies platelet
aggregation

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5
Q

ADENOSINE (P2Y12) RECEPTOR ANTAGONISTS

Examples

A

Ticlopidine: first to be introduced
- Causes neutropenia and thrombocytopenia limiting its clinical use

Main drugs
- Clopidogrel, prasugrel
, Irreversible inhibition of P2Y12 receptors

-Ticagrecol
 Reversible, non-competitive inhibitor of P2Y12 receptors

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6
Q

‘Clopidogrel, prasugrel, ticagrecol MoA

A

Clopidogrel is a prodrug
- Converted into its active sulfhydryl metabolite by CYP enzymes in the liver including CYP2C19
- Patients with variant alleles of CYP2C19 (poor
metabolisers) are at increased risk of therapeutic
failure
- Potential for interaction with other drugs (e.g.
omeprazole) metabolised by CYP2C19
- Current labeling recommends against use with proton pump inhibitors for this reason

Prasugrel and ticagrecol action is more
independent of CYP450 variations

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7
Q

ADVERSE EFFECTS

ADENOSINE (P2Y12) RECEPTOR
ANTAGONISTS

A
  • Increased risk of hemorrhage ‘’
  • Serious blood dyscrasias are rare
  • Dyspepsia
    -, Diarrhea
  • Rash
  • Angioedema
  • Dyspnea
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8
Q

‘DIPYRIDAMOLE
Inhibits platelet aggregation by several mechanisms

A

 Inhibition of phosphodiesterase (PDE)
 Blockade of adenosine uptake
 Inhibition of TXA 2 synthesis

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9
Q

DIPYRIDAMOLE also used in + one disadvantage

A

‘-Vasodilator-angina prophylaxis
-Clinical effectiveness has been uncertain
• Reduced risk of stroke and death in transient ischemic attacks (15%)—similar to aspirin

[ not that effective]

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10
Q

DIPYRIDAMOLE
Main side effects

A

‘ Dizziness, headache and GI disturbances
 Unlike aspirin, it does not increase risk of bleeding

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11
Q

GLYCOPROTEIN IIB/IIIA RECEPTOR ANTAGONISTS
Examples

A

-Abciximab (IV)
-Tirofiban: synthetic non-peptide
-Eptifibatide: cyclic peptide based on the Arg–
Gly–Asp (‘RGD’) sequence ligand binding site

They Should inhibit all pathways of platelet
activation

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12
Q
  1. Abciximab (IV)
    Is what
A

Hybrid murine–human monoclonal
antibody Fab fragment

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13
Q

Abciximab (IV)

A

-Use in high-risk patients undergoing
coronary angioplasty, as an adjunct to
heparin and aspirin
-Reduces risk of restenosis at expense
of increased risk of bleeding
- Immunogenicity limits its use to a
single administration

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14
Q

Tirofiban + eptifibatide
Clinical use + route of administration

A

-Given IV as adjunct to aspirin and a heparin
preparation
- Reduce early events in acute coronary syndrome
- Use in high-risk patients undergoing coronary
angioplasty

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15
Q

Adverse effects of GLYCOPROTEIN IIB/IIIA RECEPTOR ANTAGONISTS

A
  • Increase the risk of bleeding
  • May cause thrombocytopenia
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16
Q

OTHER ANTIPLATELET DRUGS

A

Epoprostenol (PGI 2)

17
Q

Epoprostenol (PGI2) what is it

A

-IV infusion
-Agonist at prostanoid IP receptors
•Causes vasodilatation
• Inhibits platelet aggregation

18
Q

Epoprostenol (PGI 2)
Clinical uses

A

Clinical uses
- Added to blood entering the dialysis circuit to prevent thrombosis during haemodialysis
-Severe pulmonary hypertension
- Circulatory shock

19
Q

Adverse effects of Epoprostenol

A

flushing, headache, hypotension

20
Q

Main anti platelet drug:
And second line tx:

A

1.Aspirin
- dipyridamole, clopidogrel
( can be used in pts. Who are intolerant of aspirin)

21
Q

Antiplatelet drug uses:

Relate mainly to arterial thrombosis

A
  • Acute MI
  • high risk of MI, hx of MI,, angina, intermittent claudication
  • after coronary artery bypass grafting
  • unstable Coronary syndromes (clopidogrel w/ aspirin)
  • after coronary artery angioplasty (abciximab w/ aspirin)
  • transient cerebral ischaemic attack (mini strokes) or thrombotic thrombotic stroke to prevent recurrence (dipyridamole w/ aspirin)
  • Afib if oral anticoagulant is CO
  • epoprostenol : in haemodialysis
22
Q

FIBRINOLYSIS (THROMOBOLYSIS)

A

 Fibrinolytic system set in motion with
coagulation system activation
 Via endogenous plasminogen activators
 Plasminogen is deposited on the fibrin strands
within a thrombus
 Plasminogen activators diffuse into thrombus
and cleave plasminogen to release plasmin
 Plasmin digests not only fibrin but fibrinogen;
factors II, V and VIII; and many other proteins

23
Q

FIBRINOLYTIC DRUGS use

A
  • Principally used to reopen occluded
    arteries in patients with acute MI or stroke
    • Now less widely used in acute myocardial
    infarction: emergency angioplasty service
  • Less commonly in patients with life-
    threatening VT or PE
24
Q

STREPTOKINASE

A

Extracted from streptococci
 Activates plasminogen

25
Q

STREPTOKINASE
Clinical use

A

IV infusion
- Reduces mortality in acute MI
- Additive beneficial effects with aspirin

  • Action blocked by antibodies 4 days or more
    after the initial dose
    •Its use should not be repeated after this time has
    elapsed
26
Q

Recombinant Tissue Plasminogen Activator (tPA)
Examples

A

Alteplase, duteplase, reteplase

-More active on fibrin-bound plasminogen than on
plasma plasminogen: ‘clot selective’
- Not antigenic

27
Q

Alteplase, duteplase, reteplase: recombinant tPA
Clinical use

A

-IV infusion
- Available for clinical use in MI, acute ischemic stroke

28
Q

Alteplase, duteplase, reteplase: recombinant tPA
+ streptokinase

ADVERSE EFFECTS

A
  • Bleeding
    • GI haemorrhage and haemorrhagic stroke
  • May be treated with aminocaproid and
    tranexamic acids, fresh plasma or
    coagulation factors
  • Streptokinase: allergic reactions and low-
    grade fever, hypotension
29
Q

Fibrinolytic drug use ( streptokinase, altepase)

A
  • main use: acute thrombotic stroke within 3h of onset
  • Clearing thromboses shunts and cannulae
  • acute art. Thromboembolism
  • DVT and Pulm. Embolism (streptokinase)
30
Q

ANTIFIBRINOLYTIC AND HAEMOSTATIC DRUGS

A

Tranexamic acid

31
Q

Tranexamic acid MoA + route of Admin.

A
  • Inhibits plasminogen activation
  • Prevents fibrinolysis
  • Can be given orally or IV
32
Q

Tranexamic acid clinical uses

A
  • Used to treat various conditions in which there is bleeding or risk of bleeding
    • Haemorrhage following prostatectomy or dental extraction
    • Menorrhagia (excessive menstrual blood loss)
    •Life threatening bleeding following thrombolytic drug administration

Sys. Pharm Week4 (2 decks)

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