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Haem > Pharmacology for clotting > Flashcards

Pharmacology for clotting Flashcards

1
Q

MOA of dipyridamole

A
  • Inhibits platelet activation and aggregation by increasing cAMP through:
  • Inhibiting adnosine reuptake -> more A2 receptor activation on platelets to increase cAMP production
  • Inhibiting PDE3 -> reduce cAMP degradation
  • Also causes dose-limiting vasodilation (used for myocardial perfusion imaging)
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2
Q

Onset of dipyridamole

A
  • Fast onset (20-30 mins after PO administration)
  • Peak in 2-2.25 hours
  • Short duration of treatment (3 hours)
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3
Q

ADR of dipyridamole

A

Vasodilatory:
- Headache
- Hypotension
- Dizziness
- Flushing

Others:
- GIT (N,V,D)

Cautions:
- Caution in pts with hypotension or severe CAD
- Hypersensitivity

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4
Q

DDI of dipyridamole

A
  • Increases serum adenosine levels
  • Reduce cholinesterase inhibitors levels (aggravates myasthenia gravis)
  • Increased risk of bleeding with heparin and other anticoagulants / antiplatelets
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5
Q

MOA of aspirin

A
  • Irreversible, non-selective COX inhibitor (COX1 > COX2)
  • Inhibits production of TXA2 in platelets (via COX1) and PGI2 in endothelial cells (via COX2)
  • Loses selectivity at high dose (low dose ~40-160 mg daily more effective than high dose ~500-1000mg daily)
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6
Q

ADR of aspirin

A
  • Upper gI events
  • Increased bleeding & bruising

Cautions:
- Caution in patients with platelet & bleeding disorders

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7
Q

DDI of aspirin

A
  • Increased risk of bleeding with other anti platelets / anticoagulants
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8
Q

Time of onset for aspirin

A
  • 3-4 hours onset after new COX-2 enzymes are regenerated to produce PGI2
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9
Q

MOA of clopidogrel & ticagrelor

A

Binds to P2Y12 receptor, preventing ADP-mediated activation of GPIIb/IIIa receptors, which regulates platelet activation and aggregation

Clopidogrel:
- Prodrug
- Irreversible binding at ADP binding site

Ticagrelor:
- Active drug & metabolites
- Reversible binding to allosteric site to inhibit G protein activation & cell signalling

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10
Q

Onset of clopidogrel

A
  • Delayed (6-8 hours)
  • Affected by CYP2C19 phenotype
  • Effect lasts for the lifetime of the platelets (7-10 days)
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11
Q

Onset of ticagrelor

A
  • Faster onset & peak
  • Recovery of effect takes 2-3 days
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12
Q

ADR of clopidogrel

A
  • Hemorrhage, bleeding (including intracranial bleeding)
  • Easy bruising
  • Dyspepsia
  • Rash
  • Bronchospasm & dyspnea
  • Hypotension

Cautions:
- Contraindicated in pts with active bleeding
- Caution for pts at high risk of bleeding
- Caution for CYP2C19 IM/PM

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13
Q

ADR of ticagrelor

A
  • Hemorrhage, bleeding (including intracranial bleeding)
  • Easy bruising
  • Bradycardia
  • Dyspnea, cough

Cautions:
- Contraindicated in pts with severe liver impairment, breastfeeding women
- Contraindicated in pts with h/o intracranial hemorrhage or active bleed
- Caution in pts with risk of bleeding, elderly and moderate hepatic failure

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14
Q

DDI of clopidogrel

A
  • Warfarin, NSAIDs and salicylates (increased bleeding risk)
  • Macrolides (reduced effect)
  • Strong/moderate CYP2C19 inhibitors (reduced effect)
  • Rifamycin (increased effect)
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15
Q

DDI of ticagrelor

A
  • Anticoagulants, fibrinolytic, long-term NSAIDs (increased bleeding risk)
  • Aspirin dose >100 mg/day (reduced ticagrelor effect but increased bleed risk)
  • CYP3A inducers e.g. dexamethasone, phenytoin (reduced ticagrelor effect)
  • CYP3A strong inhibitors e.g. clarithromycin, ketoconazole (increased ticagrelor effect)
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16
Q

MOA of warfarin

A
  • Inhibits VKORC1 which activates vit K for the carboxylation (reduction) of glutamic acid on factors II, VII, IX, X
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17
Q

Onset of warfarin effect

A
  • 24-72 hours after PO administration
  • Peak reached in 2-8 hours
  • Full effect reached in 5-7 days
  • Duration of action: 2-5 days
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18
Q

Metabolism of warfarin

A
  • Hepatic metabolism
  • CYP2C9
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19
Q

Elimination of warfarin

A
  • 20-60 hours
  • High inter individual variability
  • Excreted through urine & feces
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20
Q

ADR of warfarin

A
  • Hemorrhage, bleeding
  • Hepatitis
  • Cutaneous necrosis and infarction of the breast, butt, extremities (usually 3-5 days after start)
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21
Q

Contraindications & cautions of warfarin

A

Contraindications:
- Hypersensitivity
- Active bleeding, risk of bleed, after recent major surgery
- Severe / malignant hypertension
- Severe renal / hepatic disease
- Subacute bacterial endocarditis, pericarditis, pericardial effusion
- Pregnancy

Cautions:
- Breastfeeding
- Diverticulitis, colitis
- Mild/moderate hypertension
- Mild/moderate renal or hepatic disease
- On drainage tubes in any orifices

22
Q

DDI of warfarin

A
  • Other anticoagulants, antiplatelets, NSAIDs, SSRIs
  • Long-term high dose paracetamol therapy (>2 g per day for >2 weeks)
  • CYP2C9 inhibitors (amiodarone, flu/voriconazole, fluorouracil, metronidazole, bactrim)
  • CYP2C9 inducers (barbiturates, carbamazepine, rifampicin, st john’s wort, ritonavir)
  • CYP3A4 inhibitors
  • CYP3A4 inducers
  • Other drugs (PPI, allopurinol, spironolactone, thiazides)
  • Traditional meds, herbs e.g. gingko, ginseng, reishi mushroom
  • Foods, supplements e.g. vit K supplement, green tea, vit K-rich food, cranberry juice
23
Q

Reversal of warfarin effect

A

Vit K

24
Q

MOA of dabigatran

A
  • A prodrug (dabigatran etexilate)
  • Dabigatran & acyl glucuronides are competitive, reversible non-peptide antagonists of thrombin (factor IIa)
25
Q

Reversal of dabigatran effect

A
  • Idarucizumab
  • Binds to dabigatran & its acyl glucuronides with higher affinity than thrombin
26
Q

MOA of rivaroxaban

A
  • Competitive reversible antagonist of activated factor X
27
Q

Reversal of rivaroxaban effect

A
  • Andexanet alfa
  • Recombinant human factor Xa
28
Q

Oral bioavailability of dabigatran & rivaroxaban

A

Dabigatran: 3-7%
Rivaroxaban: 80-100%

29
Q

Peak action of dabigatran & rivaroxaban

A

Dabigatran: 3 hours
Rivaroxaban: 2.5-4 hours

30
Q

Metabolism of dabigatran & rivaroxaban

A

Dabigatran: nil
Rivaroxaban: hepatic

31
Q

Elimination of dabigatran & rivaroxaban

A

Dabigatran:
- Excreted through urine
- t1/2: 12-17 hours

Rivaroxaban:
- Excreted through urine (66%) and feces (28%)
- t1/2: 5-9 hours

32
Q

ADR of dabigatran & rivaroxaban

A

Dabigatran: bleeding, GI symptoms
Rivaroxaban: bleeding

33
Q

DDI of dabigatran

A
  • Antiplatelets, anticoagulants, fibrinolytic (increased bleed risk)
  • NSAIDs, ketoconazole (increased bleed risk)
  • Rifampin (reduced dabigatran levels)
34
Q

DDI of rivaroxaban

A
  • Antiplatelets, anticoagulants (increased bleed risk)
  • NSAIDs, PGP & CYP3A4 inhibitors (increased bleed risk)
  • PGP & CYP3A4 inducers (reduced rivaroxaban levels)
35
Q

Reversal of dabigatran & rivaroxaban effects

A

Dabigatran: 3-5 days
Rivaroxaban: 2-3 days

36
Q

MOA of heparin

A
  • Potentiate the action of antithrombin III, thus inactivating thrombin
  • Heparin binds to AT III and causes a conformational change to expose AT III’s active site for more rapid protease interaction

Heparin:
- Hepatin-AT III inactivates thrombin, factors IXa, Xa, XIa, XIIa

Enoxaparin:
- More selective for Xa

37
Q

Route of administration for heparin & LMWH

A

IV, SC

38
Q

Absorption of heparin & LMWH

A

Heparin:
- MW: 15000
- F: 30%

LMWH:
- MW: 5000
- F: 80-90%

39
Q

Elimination of heparin & LMWH

A

Heparin:
- t1/2: 1 hr
- Nil renal excretion

LMWH:
- t1/2: 4 hr
- Renal excretion

40
Q

ADR of heparin & LMWH

A
  • Bleeding
  • Increased risk of epidural & spinal hematomas & paralysis in epidural/spinal anaesthesia or spinal puncture procedures
  • Heparin-induced thrombocytopenia (less with LMWH)
41
Q

Anticoagulant for pregnancy

A

Heparin, LMWH

42
Q

Cautions for Heparin & LMWH

A

Contraindications:
- Hypersensitive to heparin / pork
- Active major bleeds
- Thrombocytopenia or presence of anti platelet antibodies

Caution:
- Elderly
- Risk of bleed (prosthetic heart valves, major surgery, regional / lumbar block anaesthesia, recent childbirth, blood dyscrasia, pericarditis, pericardial effusion, renal insufficiency)

43
Q

DDI for heparin & LMWH

A
  • Antiplatelets, anticoagulants, fibrinolytic, NSAIDs (increased bleed risk)
  • SSRI (increased bleed risk)
  • Chamomile, fenugreek, garlic, ginger, gingko, ginseng (increased bleed risk)
44
Q

MOA of alteplase

A
  • A recombinant tissue plasminogen activator
  • Binds preferentially to clot-associated plasminogen and activates it to plasmin for fibrinolysis
45
Q

Reversal of heparin effect

A
  • Protamine sulfate
  • Basic
  • Binds to -ve charged heparin
  • But incomplete reversal for LMWH
46
Q

Duration of action of alteplase

A
  • 20-30 mins
  • Longer half-life than endogenous tPA
47
Q

ADR of alteplase

A
  • Hemorrhage, bleeding
  • Ventricular arrhythmias, hypotension, edema
  • Cholesterol embolisation, venous thromboembolism
  • Hypersensi
48
Q

Cautions for alteplase

A

Contraindication:
- Patients with active bleed
- Prior intracranial hemorrhage
- Recent intracranial / intrainspinal surgery in the last 3 months
- Serious head injury
- Stroke

Caution:
- Major surgery within 10 days
- Risk of bleed (e.g. peptic ulcer)
- Cerebrovascular disease
- Mitral stenosis
- Atrial fibrillation
- Acute pericarditis or subacute bacterial endocarditis

49
Q

DDI for alteplase

A
  • Antiplatelets (especially dipyridamole, aspirin) and anticoagulants (especially warfarin & heparin) (increased bleed risk)
  • Nitroglycerin (reduced alteplase levels)
50
Q

Reversal of alteplase effect

A
  • Tranexamic acid and aminocaproic acid
  • Compete for lysine binding site on plasminogen & plasmin
  • Prevents interaction with fibrin

Haem (5 decks)

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