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Drugs > Haematology Drugs > Flashcards

Haematology Drugs Flashcards

1
Q

Definition of venous thrombosis and treatment

A

Intravascular clot(red) forms in deep veins, particularly of the legs, when flow is sluggish. Fragment may bud of (embolus) and block blood vessels, often pulmonary artery

Therapy : anticoagulant drugs

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2
Q

Definition of arterial thrombosis and treatment

A

Platelets aggregate (white) usually at site of ruptured atherosclerotic plaque, then encapsulated by clot (red)

Therapy:

  • *Immediate-** dissolve existing clots with thrombolytics(fibrinolytics)
  • *long term** – antiplatelet drugs (anti-thrombolytics)
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3
Q

Haematolgical drugs categories

A

Thrombolytic drugs

  • rt-PA
  • streptokinase

Anticoagulant drugs

  • Heparins- (Unfractionated/ low molecular weight)
  • Warfarin -
  • Rivarobiban, apixaban - Factor Xa anatagonists
  • Dabgigatran - direct thrombin inhibitors

Antiplatelet drugs

  • Aspirin
  • Clopidogrel
  • Dipyridamole
  • Tirofiban
  • Abciximab
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4
Q

Oral anti-coagulants/ vitamin K antagoinst Example

A

Warfarin

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5
Q

Warfarin mechanism of action

A
  • Extrinsic pathway
  • Inhibits vitamin K epoxide reductase
  • Prevents recycling of Vitamin K to reduced form after carboxylation of coagulation factors II, VII, IX and X
  • Prevents thrombus formation
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6
Q

Indication of warfarin

A
  • Treatment of venous thromboembolism
  • Thromboprophylaxis in: AF/metallic heart valves/ Cardiomyopathy
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7
Q

Side effects of warfarin

A
  • Bleeding (risk increases with increasing INR)
  • Warfarin necrosis
  • Osteoporosis
  • crosses BBB
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8
Q

Important pharmacokinetics/pharmacodynamics of warfarin

A
  • Orally active (more convenient than heparin)
  • Numerous drug interactions / food interactions
  • Reversal by giving vitamin K
  • Polymorphisms in key metabolising enzymes (VKORC1 and CYP2C9)
  • Needs therapeutic drug monitoring and monitored loading regimen
  • Monitored with INR and dose adjusted according to indication
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9
Q

Patient information of warfarin

A
  • Need for compliance / attendance at visits for monitoring
  • Care needed with alcohol
  • Must inform doctor before starting new drugs – avoid over the counter aspirin preparations
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10
Q

How to reverse side effects of warfarin

A
  • Transfuse with plasma or coagulation factor concentrates
  • Oral vitamin K- but reversal is slow- require carboxylation to resume (1-3days)
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11
Q

Two types of heparin

A
  • Unfractionated heparin
  • Low molecular weight heparin
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12
Q

Unfracionated heparin mechanism

A
  • Intrinsic pathway
  • Enhances activity of antithrombin III. (natural anticoagulant)
  • Antithrombin III inhibits thrombin.
  • Heparins also inhibit multiple other factors of the coagulation cascade.
  • Immediate inhibition of clotting
  • This produces its anticoagulant effect.
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13
Q

Indication of unfractionated heparin

A
  • Treatment and prophylaxis of thromboembolic diseases, including induction of vitamin K antagonists.
  • Renal dialysis (haemodialysis)
  • Acute Coronary Syndrome treatment
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14
Q

Side effects of unfractionated heparin

A
  • Bleeding (Major haemorrhage risk can be as high as 3.5%)
  • Heparin-induced thrombocytopenia
  • Osteoporosis
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15
Q

Important PD/PK of unfractionated heparin

A
  • Administered by continuous intravenous infusion or subcutaneous injection
  • Complex kinetics - non-linear relationship between dose / half-life and effect – needs TDM
  • Effect monitored using activated partial thromboplastin time (aPTT)
  • Anticoagulant effect can be reversed with protamine.
  • Unfractionated heparin has a shorter duration of action than LMW Heparin.
  • Used in preference to LMW Heparin, in selected patients, due to the shorter duration of action and reversability with protamine (for example, Peri-operatively.
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16
Q

Patient information of pharmacokinetics/ pharmacodynamics

A
  • Risk of bleeding
  • Regular blood monitoring required
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17
Q

Low molecular weight heparin mechanism of action

A
  • Enhances activity of antithrombin III.
  • Antithrombin III inhibits thrombin.
  • Heparins also inhibit multiple other factors of the coagulation cascade.
  • This produces its anticoagulant effect
  • LMWH inhibits factor X only
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18
Q

Indication of low molecular weight heparin

A
  • Treatment and prophylaxis of thromboembolic diseases, including induction of vitamin K antagonists.
  • Renal dialysis (haemodialysis)
  • Acute Coronary Syndrome treatment
  • low-molecular-weight heparins do not prolong the APTT; they have a predictable anticoagulant effect and do not require monitoring unless in long-term use; in this case use the factor Xa assay to assess the degree of anticoagulation
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19
Q

Side effects of LMWH

A
  • Bleeding (Major haemorrhage risk can be as high as 3.5%)
  • Heparin-induced thrombocytopenia (Less risk than unfractionated heparin)
  • Osteoporosis (Less risk than unfractionated heparin
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20
Q

Important pharmacokinetcis/ pharmaco dynamics of LMWH

A
  • Subcutaneous injection - not orally active
  • More predictable dose-response relationship than Unfractionated Heparin.
  • 2-4 times longer plasma half-life than Unfractionated Heparin
  • Clearance is mostly via a renal pathway, thus the half-life can be prolonged in patients with renal failure, so dose adjustment may be needed.
  • Regular coagulation monitoring is not required.
  • Less readily reversed with protamine, than Unfractionated Heparin.
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21
Q

Patient information of LMWH

A
  • Risk of bleeding
  • Requires injection
  • Will need blood testing in prolonged therapy (Full Blood Count, to monitor for thrombocytopenia)
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22
Q

How are the anticoagulants monitored?

A

Warfarin- measured using INR ratio

Heparin measured using the APTT (activated partial thromboplastin time) test

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23
Q

Anti-platelet drugs examples

A
  • Aspirin
  • clopidogrel
  • dipyrimadole
  • Ticagrelori
  • Tirofibran
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24
Q

Aspirin Mechanism of action

A
  • Irreversible inactivation of cyclooxygenase (COX) enzyme
  • This reduces platelet thromboxane (TXA2) production and endothelial prostaglandin (PGI2) production
  • Reduced platelet thromboxane production reduced platelet aggregation and thrombus formation
  • Reduced prostaglandin synthesis decreases nociceptive sensitisation and inflammation
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25
Q

Indication of aspirin

A
  • Secondary prevention of thrombotic events
  • Pain relief
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26
Q

Side effects of aspirin

A
  • Bleeding (<1% Patients)
  • Peptic ulceration
  • Angiooedema
  • Bronchospasm
  • Reye’s syndrome (very rare)
27
Q

Important pharcokinetics/pharmacodyanmics of aspirin

A

Half life becomes longer with very large doses (pharmacokinetics may be non-linear in overdose)

28
Q

Avoid over the counter preparations of aspirin

A

Avoid over the counter preparations that contain aspirin.
Some patients may be advised to take a Proton Pump Inhibitor alongside long-term aspirin

29
Q

Clopidogrel mechanism of action

A
  • Irreversibly blocks the ADP-receptor on platelet cell membranes.
  • Consequently inhibits formation of GPIIb/IIIa complex, required for platelet aggregation.
  • Decreased thrombus formation.
30
Q

Indication of clopidogrel

A

Secondary prevention of thrombotic events

31
Q

Side effects of clopidogrel

A
  • Bleeding (1-10% of Patients)
  • Abdominal pain / diarrhoea (1-10% of Patients
32
Q

Important pharacokinetics/pharmacodynamics of clopidogrel

A

avoid in liver failure

33
Q

patient information of clopidogrel

A
  • Patients may be advised to stop clopidogrel before surgical procedures.
  • Patients should not stop clopidogrel without consulting their doctor if they have an arterial stent in-situ
34
Q

Mechanism of action of dipyradimole

A
  • Inhibits cyclic nucleotide phosphodiesterases à increase cyclin AMP and increases cGMP )potentiates prostacyclin and NO)
  • So inhibits platelet activation
35
Q

Indication of dipyradimole

A

dipyridamole is used in conjunction with warfarin and other anti-coagulants in the prophylaxis against thrombosis associated with prosthetic heart valves

36
Q

Adverse effects of dipyridamole

A
  • hyoptension
  • nausea
  • diarrhoea
  • headache
37
Q

Examples of glycoprotein IIb/IIIa inhibitors

A
  • abciximab
  • tirofiban
38
Q

Mechanism of action of abciximab

A
  • monoclonal antibody fragment
  • directed towards the glycoprotein IIb/IIIa receptor of platlets
  • binding and inactivation of this receptor prevents platelet aggregation
39
Q

Indication of abciximab

A
  • Used during surgical exploration/ clearing of intravascular blockage e.g coronary artery thrombosis
  • Antigenic- can be used once only
40
Q

Side effects of abciximab

A
  • haemorrhage
  • nausea
  • vomitting
  • hypotension
41
Q

Mechanism of action of tirofiban

A
  • Tirofiban prevents the blood from clotting during episodes of chest pain or a heart attack, or while the patient is undergoing a procedure to treat a blocked coronary artery.
  • It is a non-peptide reversible antagonist of the platelet glycoprotein (GP) IIb/IIIa receptor, and inhibits platelet aggregation.
42
Q

Indication of tirofiban

A
  • For treatment, in combination with heparin, of acute coronary syndrome,
  • including patients who are to be managed medically and those undergoing PTCA or atherectomy.
43
Q

Dabagitran mechanism of action

A
  • Direct thrombin inhibitor; prevents conversion of fibrinogen to fibrin
  • prevents thrombus formation
44
Q

Indication of dabigatran

A

Prophylaxis of venous thromboembolism (especially post-operative)
Thromboprophylaxis in non-valvular A

45
Q

Side effects of dabigatran

A
  • Bleeding
  • Dyspepsia
46
Q

Important PK/PD of dabagitran

A
  • Rapid onset of action
  • No food / few drug interactions (not metabolised via CYP 450)
  • No need for therapeutic monitoring
  • Currently no available antidote
47
Q

Patient information of dabagitran

A

risk of bleeding

48
Q

Rivaroxaban mechanism of action

A
  • Inhibits conversion of prothrombin to thrombin, reducing concentrations of thrombin in the blood.
  • This inhibits the formation of fibrin clots.
49
Q

Indication of rivaroxiban

A
  • Prophylaxis of venous thromboembolism (especially post-operative)
  • Thromboprophylaxis in non-valvular AF
  • Treatment of venous thromboembolism
50
Q

Side effects of rivaroxiban

A
  • bleeding
  • nausea
51
Q

Important pharmacokinetics/pharmacodynamics of rivaroxaban

A
  • Predictable drug interactions (metabolised via CYP 450, inc CYP3A4)
  • No need for therapeutic monitoring
  • Currently no available antidote
52
Q

Patient information about rivaroxaban

A

risk of bleeding

53
Q

Apixaban mechanism of action

A
  • Inhibits conversion of prothrombin to thrombin; reducing concentrations of thrombin in the blood.
  • This inhibits the formation of fibrin clots
54
Q

Indication of apixaban

A
  • Prophylaxis of venous thromboembolism following hip or knee replacement surgery.
  • Thromboprophylaxis in non-valvular AF.
55
Q

side effects of apixaban

A
  • bleeding
  • nausea
56
Q

Important pharmacokinetics/pharmaodynamics of apixaban

A
  • Predictable drug interactions (metabolised via CYP 450 and substrate for p glycoprotein)
  • 75% is metabolised by the liver, the rest being renally excreted.
  • No need for therapeutic monitoring
  • Currently no available antidote.
57
Q

Patient information of apixaban

A

risk of bleeding

58
Q

Examples of recombinant tissue plasminogen activators (rtPA)

A

Tenecteplase

alteplase

These drugs are thrombolytics/fibrinolytics

59
Q

Mechanims of action of rtPA

A
  • Recombinant form of tissue plasminogen activator
  • Catalyses conversion of plasminogen to plasmin
  • Promotes fibrin clot lysis
60
Q

Indication of rtPA

A
  • Acute ischaemic stroke within 4.5 hours of onset
  • Myocardial infarction within 12 hours of onset
  • Massive pulmonary embolism
  • N.B Not all thrombolytic drugs are licenced for all of these indications
61
Q

Side effecs of rtPA

A

Bleeding
Allergic reaction / angiooedema (1%)

62
Q

Important pharmacokinetics/pharmacodynamics of rtPA

A
  • Bolus-infusion regimen is used for alteplase
  • Tenecteplase is given as a single bolus
  • Pharmacodynamic interactions with other blood thinners (antiplatelets / anticoagulants)
63
Q

Patient information of rtPA

A
  • When using thrombolytic drugs, patients should be made aware of the risk-benefit ratio, which should include reference to the rate of bleeding complications

Drugs (8 decks)

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